Immunology Part 3

T cells and cancer survival

having lots of T cells at both the center and the invasive margin of the tumor means that the patient has a very good chance of long term (10 year) survival

IgE mediated allergy

Also known as type I hypersensitivity • Requires prior exposure and sensitization (IgE)

Oral Allergy Syndrome

Gastrointestinal Food Hypersensitivity • Localized reaction with pruritus, sometimes swelling of the mouth, lips, throat • Due to fresh fruits and vegetables that cross-react with specific pollens • Reactions do not occur with cooked products

Diagnostic Features of Eczema

Essential •Pruritus •Typical morphology and Age Specific Patterns o Infants: face, neck, extensor surfaces o Any age group: flexural surfaces o Sparing of groin or axillary region •Chronic Relapsing Course Important •Early age of onset •Xerosis = dryness •May have atopy o Personal or family history o IgE reactivity Note: appears in popliteal fossa Treatment of Eczema • Moisturizers to promote skin hydration • Topical anti-inflammatory medications • Allergen avoidance • Treatment and prevention of superinfection Eczema itself may lead to or predispose the allergy

Syngeneic

Same genome, e.g. monozygotic twins or inbred mice. Genetically compatible for transplant purposes.

Detection of Allergen Specific IgEMediated Sensitivity

Skin testing: wheal and flare responses Blood testing: measurement of serum specific IgE levels -Wheal of the wheal and flare is caused by edema resulting from histamine-induced capillary permeability

Allergic Reaction Pathophysiology

Mediated by allergen binding surface-bound specific IgE on mast cells and basophils. Cell degranulation occurs when antigen crosslinks IgE. This releases "early phase" mediators within minutes which act directly on tissue (changes in vascular permeability, smooth muscle contraction) and recruit/activate additional inflammatory cells (eosinophils, basophils, others). "Late phase" reaction occurs through influx of inflammatory cells and mediators hours to days later and results in another round of vascular permeability and smooth muscle contraction, increased inflammation, remodeling of connective tissue matrix, mucus secretion.

Mast Cells

Role in IgE-mediated disease; may also serve as a regulator of innate immunity Mature and develop phenotype after arrival in the tissue Contain large cytoplasmic granules, which are filled with preformed mediators. IgE binds to FcεRI via the α chain; Crosslinking FcεRI by allergen -> Degranulation and histamine release in allergy and anaphylaxis

Inhibitors of cytokine/cytokine receptor interaction

Blockage of the IL-2/IL-2 receptor interaction Daclizumab (trade name Zenapax®) • Humanized monoclonal antibody to the IL-2Rα receptor of T cells. • FDA approval in 1997 for use in kidney transplantation (doesn't have nephrotoxicity of cyclosporine and FK506 • It is given in multiple doses --the first 1 hour before the transplant operation -- and 5 further doses given at two week intervals after the transplant A similar drug: Basiliximab

Mepolizumab (Nucala) and Reslizumab (Cinqair)

HUMANIZED Anti - IL- 5 Monoclonal Antibodies Blocking IL-5 Depletes Eosinophils in Humans

Omalizumab (Xolair)

HUMANIZED Anti - IgE Monoclonal Antibody

Inflammation & Cancer

Extent & nature of inflammation varies, but elevated inflammation tends to favor tumor progression Mechanisms: • cancer cells express cytokines that recruit immune cells • growing tumors causes cell damage - release of DAMPS - recruite immune cells • initiation of Th2 repair process - contributes to the anti-inflammatory tumor environment In an attempt to effect repair, there is angiogenesis and ECM remodeling and crosslinking (leading to stiffness) Cancer cells are restructuring the local inflammatory environment in a way that disrupts CD8 cell intervention.

Type II hypersensitivity

One of the "delayed" responses Forming IgG to antigen that is own tissue or foreign antigen that can cross react with own tissue leading to self tissue damage.

Xenogeneic

Organisms of different species. Example: Pig to human solid organ transplants.

Receptors engaged by DAMPS

-many of the receptors engaged by DAMPs are the same engaged when PAMPs are present -IL-33 and IL-25/17E produce alarmins. They are pro-inflammatory activators

Type I Reaction: Sequence of Events

1) Ag Presented 2) Th2 Response (IL-4, IL-5 and IL-13) 3) IL-4 -> IgE Production (sensitization) 4) IgE loads mast cells and basophils Sensitization (IgE production) occurs prior to the allergic reaction • Upon initial exposure, allergen/antigen is presented by Ag-presenting cells (APCs) to CD4+ Th2 cells specific to the antigen. • Th2 cells then drive B cells to produce IgE specific for the Ag (sensitization) through cytokines such as IL-4 and IL-13. This process occurs primarily in the peripheral lymphoid organs. • The specific IgE (sIgE) binds high-affinity IgE receptors (FcεRI) on mast cells and basophils.

T cell fate decisions

1) Tbet -> Th1 cell specific transcription factor that controls expression of the hallmark th1 cytokine, interferon gamma (IFN-gamma) 2) GATA3 -> induces the differentiation of Th0 cells towards the Th2 cell subtype as a transcription factor. 3) RoRgammaT -> highly restricted to expression in the thymus where it is expressed exclusively in immature CD4+/CD8+ thymocytes. DNA binding transcription factor that promotes thymocyte differentiation into pro-inflammatory T helper 17 cells (Th17 cells). 4) FoxP3 -> transcriptional regulator and functions as a master regulator of the regulatory pathway in the development and function of regulatory T cells (Tregs).

Anaphylaxis: Definition, Temporal Pattern, and Treatment

1. sudden onset of illness with involvement of skin, mucosal tissue, or both+respiratory symptoms/reduced BP 2. 2 or more organ systems involved 3. reduced BP after exposure to allergen Treatment: • Epinephrine is the drug of choice for all anaphylactic episodes. - Many patients require more than a single injection. - Different doses for children and adults. • Early and aggressive use to maintain airway, blood pressure, and cardiac output. (can give high flow O2 and saline) Other Treatment for Anaphylaxis • Antihistamines • Corticosteroids • Observe for a minimum of 4 hours After the fact, identify culprit with skin testing and IgE measuring: Must correlate with history!

The mechanism of action of CsA and FK506.

Both CsA and FK506 form complexes that block the same signal transducer: Calcineurin/protein phosphatase 2B Both target calcineurin, which has a catalytic subunit, a regulatory subunit and is regulated by calmodulin (a calcium center: if you have cytosolic calcium it becomes active and binds to various phosphatases and kinases and activates them). Cyclosporine and FK506 complexes bind to Calcineurin A/B and calmodulin in the same manner. They do not directly inhibit the active site of protein, instead they build a wall in front of the active site so they cannot bind substrate (allosteric inhibition) When T cells are exposed to CsA or FK506, the phosphatase activity of calcineurin is inhibited and NFAT remains in the cytosol even when TCR is engaged with MHCII-peptide complex. As a result, there is no secretion of cytokines such as IL2 and T cell activation is inhibited.

Pro and cons of different alternative donor sources

Cord blood wildly expensive

Immunotherapy with Checkpoints: Priming and Effector Phase

Cytotoxic T-lymphocyte associated antigen 4 (CTLA-4) is up-regulated shortly after T-cell activation and initiates negative regulation signaling on T cells during ligation with B7 costimulatory molecules expressed by antigen presenting cells. So predominantly regulates the initial stage of T cell activation. PD-1 inhibitory receptor is expressed by T cells during long-term antigen exposure and results in negative regulation on T cells during ligation with PD-L1 and PD-L2, which are primarily expressed within inflamed tissues and tumor microenvironments. The PD-1 interaction happens in the effector phase of T-cell response in peripheral tissues.

Chronic GVHD pathogenesis

Damage to thymus induced by GVHD disrupts T cell self-education in the thymus leading to chronic inflammation (autoimmune)

Direct vs. Indirect Allorecognition

Direct: even though it is an allo response, this is tight binding Indirect: presented in the context of self-MHC as foreign. this is minor histocompatibility.

What Steroids Do and Don't Do to Reduce Allergies

Do • Reduce mast cell and eosinophil numbers in the nasal mucosa Do not • Alter IgE levels or mast cell function

Immune Editing Hypothesis

Elimination: small tumors are eliminated by the immune system before they're even detectable. This can occur through NK cells, which recognize the tumor losing MHC class I, or NK activating ligands being expressed on the tumor (due to cellular stress). It can also occur due to CD8 T cells recognizing tumor antigens, which can represent either new, mutated proteins, or over-expression of a tissue-specific ligand to which tolerance is not complete. Equilibrium: Some tumors get around that, and move on to a state in which they co-exist with the immune system, in sort of an ongoing battle called equilibrium. Here the tumors try to grow, but are generally restrained by the immune system. But, for a variety of reasons, the immune system is not able to cure the tumor or eliminate it. Escape: Finally, the tumors we see in the clinic have almost certainly evolved to escape the immune system. There are a lot of ways this could happen, some of them similar to the ways virally infected cells can escape CD8 mediated attack.

CTLA-4 (CyoTotoxic Lymphocyte Antigen - 4)

For reasons not completely understood, T cells in certain environments up-regulate a molecule called CTLA-4 (CyoTotoxic Lymphocyte Antigen - 4). This is bad. CTLA-4 binds very tightly to B7 molecules, about 3 times as tightly as CD28 does. Essentially, CTLA-4 hijacks signal 2, leading to signal 1 without 2 -> i.e. anergy. Importantly, the T cells are NOT deleted, they're still there and ready to go, if only they could escape from CTLA4 Several companies have generated high affinity, human-anti human antibodies against CTLA-4. These antibodies knock CTLA-4 off B7 molecules (they bind more tightly to CTLA-4 than B7 does), and allow T cell activation to proceed. Note that this kind of therapy is predicated on the notion that patients already have some anti-tumor T cells in place. In reality: Anti-CTLA-4 Antibodies may either DEPLETE the suppressive Treg, or they may stop the from being functional Treg.

Eosinophilic Gastrointestinal Disease (EGID)

Gastrointestinal Food Hypersensitivity • Abnormal accumulation of eosinophils in the GI tract (esophagus, stomach, small intestine, colon) • Typical symptoms: poor growth, reflux, vomiting, diarrhea, abdominal pain, dysphagia, stricture • Immunopathogenesis poorly understood: IgE and non-IgE mechanisms may play a role

Inflammation

General term for the local accumulation of fluid, plasma protein, and white blood cells that is initiated by physical injury, infection, or local immune responses A homeostatic mechanism evolved to recognize cell death/tissue damage & orchestrate repair/remodeling A defense mechanism to contain and eliminate microbial pathogens that breach barriers morbidity & mortality associated with dysregulated repair/remodeling

Adoptive Cellular Therapy (ACT)

Getting the Lymphocytes From The TUMOR itself Background: Advantages of lymphocyte transfer Grow large quantities Select for high reactivity against target tumor antigen Reverse tolerizing influences in the in vivo setting Modify the host prior to transfer Modify the cells with additional tools prior to transfer You can also re-engineer a .patient's T cells to have the T cell receptor you want them to. Problem is that they already express their own T cell which can cross with the one you make and result in autoimmunity

Categories of HLA matching in HSCT

HLA-identical by descent-genotypically identical - Siblings who inherit the same haplotype from each parent HLA-identical by state-phenotypically identical; related or unrelated - 8/8 matches-HLA-A,B,C, DRB1 - 10/10 matches-HLA-A,B,C,DRB1,DQB HLA-haploidentical-e.g., parents, sibs, extended family members who share one haplotype (5/10 matches) - Partially mismatched related donors (6/10-9/10 matches

IgE Receptor/FcεR

High-Affinity IgE Receptor/FcεRI: • Tetrameric form: found on mast cells and basophils Low-Affinity IgE Receptor/ FcεRII/CD23: Found on mature B cells, activated macrophages, eosinophils, dendritic cells, and platelets May positively and negatively regulate IgE production

Types of Graft Rejection

Hyperacute - can be avoided easily; host has pre-formed antibodies to antigen in the graft. Ex: blood types. minutes to hours Acute - presence of alloantigen specific CD8 cells. Due to antibodies or activated T cells. Chronic - common; tissue response due to mostly minor histo-compatibility. Th1 T cells, IFNgamma driving a DTH (delayed type hypersensitivity) response; type IV hypersensitivity leading to macrophage activation and scarring of organ. Onion skinned look of vessels

Th2 Inflammation Tissue Repair & Remodeling

IL4 and IL13 from Th2 (and ILC2) cells activate macrophages to become M2 cells which perform wound repair and remodeling. They do this through fibroblasts which release EM repair mechanisms modulated by another group of macrophages. Within M2s there are tissue repair and tissue remodeling phenotypes -The tissue repair type communicate with fibroblasts -Remodeling ones stimulate stem cells to come in and lay down new tissue

ILC Surface & Intracellular Receptors

ILCs do not have a TCR or BCR, but do have receptors for DAMPS & cytokines -ILCs are some of the first tissue responders. -ILC2s activate in response to IL 25, 33 etc. so they are some of the first responders to the tissue damage.

Inflammation: Initiation and establishment

Initiated by tissue-resident (innate) cells that have the capacity to detect microbes (via PAMPs ) and/or cellular damage (via DAMPs & alarmins) and send alarm signals (cytokines, chemokines, complement, lipids, etc.) that recruit additional immune cells of the innate and adaptive immune system. Establish a local/regional environment that directs and facilitates transit of cells from the blood to the site of infection/injury by changes in: • blood flow • vascular permeability • endothelial adhesion • ECM composition Inflammation is activated by resident or innate cells/ we know this because it would take other cells too long to arrive and inflammation happens immediately.

Macrophage activation, metabolism & wound repair

M1 and M2 macrophages utilize different metabolic pathways. Strategies for manipulating these macrophages are based on reprogramming their metabolic status (usually in cancer therapy - supplement immune checkpoint therapies)

Chronic Inflammation

Marked by infiltrate of macrophages & lymphocytes dysregulated tissue remodeling asthma IPF cardiac fibrosis liver cirrhosis infectious fatty liver alcohol renal fibrosis tissue macrophages constantly getting signals to repair and remodel; they are constantly signaling to fibroblasts which keep making EM. this results in fibrosis. Persistent cell death or DAMPs can result in this.

Inhibitor of T cells proliferation—selective inhibitor

Mycophenolate Mofetil is a prodrug for mycophenolic acid -microbial metabolite. Highly specific and potent inhibitor of IMD (inosine monophosphate dehydrogenase). Product of this enzyme is GMP, which is a precursor of RNA and DNA synthesis. As a consequence, cells will cease to divide. • Principle of selectivity: mycophenolic acid inhibits inosine monophosphate dehydrogenase, an enzyme required for de novo purine biosynthesis. As both T and B cells rely on de novo purine biosynthesis rather than the hypoxanthine-guanine phosphoribosyl transferase salvage pathway (they lack the alternative pathway), they are selectively sensitive to inhibition of purine biosynthesis by mycophenolic acid. • Therapeutic use: Mycophenolate Mofetil has been used primarily in renal transplantation with other applications under investigation. Endothelial cells also rely on this primary pathway, thus this drug inhibits angiogenesis.

Type III Hypersensitivity

One of the "delayed" responses Immune complex mediated; also IgG mediated (other immunoglobulins don't typically form immune complexes). Complexes get deposited into tissue which activates complement leading to tissue damage and neutrophil induced inflammation. Foreign classic example=serum sickness

Type IV Hypersensitivity

One of the "delayed" responses T cell mediated; memory T cells have become sensitized to antigen. Classic: tuberculin reactions in the skin like PPD leading to activation of Th1 cells and macrophages Other classic: contact dermatitis like poison ivy; not immediate response

Provenge

Only FDA approved cancer vaccine Consists of 3 steps: 1) Take the patient's blood by leukapheresis and extract the dendritic cells 2) Incubate DCs with antigen prostatic acid phosphatase (PAP) which is present in 95% of prostate cancer cells and 3) Incubate with granulocyte-macrophage colony stimulating factor (GM-CSF) that helps APCs to mature 4) The activated blood product is reinfused into the patient.

Immune Checkpoints: PD-1

PD-1 expression is NOT really a brake by itself. T cell up-regulation of PD-1 (which is VERY characteristic of TIL) is like putting your foot over the brakes, but NOT pushing down. PD-L1 is the PUSH on the brakes, so when PD-L1 pushes on the PD-1 brake, the CD8 T cell turns off. It can't replicate, and more importantly it can not KILL it's target. As we discussed in the memory lecture, here PD-1 is a marker of exhausted, nonfunctional T cells that have been exhausted by chronic antigen exposure. PD-1 can be very effectively blocked by monoclonal antibodies against either PD-1 (the receptor) or PD-L1 (the ligand). That results in two changes in the PD-1 expressing T cells. First, the CD8 T cells reacquire their effector function, the ability to kill.

Neutrophils in the inflammatory process: egress and EM

Platelets interact with PSGL-1 clusters on polarized neutrophils Polarized neutrophils scan for activated platelets to initiate inflammation •Selectin ligand PSGL-1-transduced signals result in a redistribution of surface receptors that drive neutrophil intravascular migration •Suggests that recruited neutrophils scan for activated platelets (that are expressing P-selectin) allowing for the integration of signals present at both the endothelium & in the circulation before inflammation proceeds neutrophils displace fibrous collagen bundles from the wound center -Neutrophils release enzymes that destroy the extracellular matrix, part of the repair process is to replace that.

Allergic sensitization

Production of IgE and arming of FceRIbearing cells but does not imply clinical disease

"Vector" Vaccine for Cancer

ProstVac VF here the vaccine target is Prostate Specific Antigen (PSA), which is also expressed by nearly all prostate tumors. In order to make the antigen presenting cells that present PSA as an antigen to T cells work better, the vaccine also includes THREE molecules to enhance co-stimulation. One is the molecule that interacts with CD28 on T cells, B7-1. Excellent. The other two molecules help T cells adhere more tightly to the DC infected by the vaccine, these are ICAM-1 (which binds to LFA-1 on T cells), and LFA-3 which binds to CD2 (LFA-2) on T cells and is important in strengthening the adhesion between T cells and APCs. Unfortunately, failed to work in the ProstVac phase III trial

Inflammatory Cell Death types

Pyroptosis -Downstream of activation of inflammasomes. Done largely through caspase 1 (11 in mouse) cleavage which through gas D leads to the creation of pores. Leads to leaking of intracellular components that are DAMPS. -DAMPs engage receptors on immune cells to initiate inflammation Necroptosis -RIP-1 and RIP-3 mediate Necroptosis. MLKL forms pores -DAMPs engage receptors on immune cells to initiate inflammation Ferroptosis -iron-dependent type of cell death that is activated in cancer cells by endogenous stimuli & exogenous agents

Inhibitors of cytokine receptor mediated signal transduction

Rapamycin blocks IL-2 dependent T cell proliferation. Rapamycine had anti-fungal activity. There are currently 2 versions: -sirolimus -everolimus Rapamycin bears structural similarity to FK506. Like FK506, rapamycin also binds to FKBP. Unlike FK506, however, the FKBP-rapamycin complex does not affect calcineurin. Instead, the FKBP-rapamycin complex inhibits another protein, known as RAFT (Rapamycin and FKBP Target)/FRAP (FKBPRapamycin Associated Protein)/TOR (Target Of Rapamycin). This rapamycin target is a phospholipid kinase superfamily member and is involved in regulating both transcription and translation of a number of genes required for T cell proliferation. mTOR is a protein kinase. Brings FKBP to mTOR, preventing mTOR from accessing proteins. mTORC is a multiprotein complex that senses anergy state, growth factors, cell proliferation, etc. If you block mTORC you block proliferation

Other T cell inhibitors

Steroids Glucocorticoids are still being used as an immunosuppressants, due in part to their ability to inhibit T cell activation by blocking cytokine gene expression. Prednisone remains a widely prescribed immunosuppressant. -inhibit NFkB and do not show nephrotoxicity Cytotoxic drugs T cells are susceptible to non-specific inhibition by cytotoxic drugs, which are also used as anti-neoplastic products. These include azathioprine and cyclophosphamide. These drugs have severe side effects and have been largely replaced by the more specific immunusuppressants such as CsA and FK506.

TCR Anti-cancer affinity

T Cell/MHC+peptide interactions are very low affinity. They're in the MICROmolar range, while antibodies are usually in the nanomolar (sometimes even sub-nanomolar range). TCR's specific for cancer are even worse than average, probably because of negative selection of high-affinity receptors in the thymus and periphery. Answer: Chimeric Antigen Receptor -combine the specificity and tightness of binding of an antibody, with the killing machinery engaged by a CD8 T cell -have an extracellular domain from a high-affinity antibody, the transmembrane domain of the co-stimulation molecule CD28, the zeta chain that's critical for T cell activation AND some extra sauce

Allogeneic

Taken from different individuals of the same species. Typical transplants between non-twin humans.

Laboratory Measurement of allergen-specific serum IgE (formerly called "RAST" for RadioAllergo-Sorbent-Test)

The allergen of interest, covalently coupled to the solid phase, reacts with the specific IgE in the patient' s serum sample. After washing away non-specific IgE, enzyme-labeled antibodies against IgE are added to form a complex After incubation, unbound enzymelabeled anti-IgE is washed away and the bound complex is then incubated with a developing agent. After stopping the reaction, the fluorescence of the eluate is measured. The higher the fluorescence, the more specific IgE is present in the sample.

Sites of inhibition by immunosuppressants

The currently used immunosuppressants block different sites of the immune activation cascade. They are centered around CD4 T cells. The different sites include: 1. T cell surface receptors to prevent the engagement of TCR with MHC-peptide complex on antigen presenting cells. 2. Intracellular signal transduction pathways from TCR to the nucleus to activate cytokine production. 3. T cell surface receptor involved in the interaction between cytokines and cytokine receptors to initiate T cell proliferation and clonal expansion. 4. Intracellular signal transduction pathways emanating from cytokine receptors. 5. General T cell proliferation.

Alloreactivity

The immune response against "allo" antigens, differing due to alleles at same locus (MHC & minor determinants)

Primary Immunodeficiency

The primary immunodeficiency diseases are a heterogenous group of disorders that affect virtually every major component of the immune system. The term PRIMARY refers to the fact that the defect is intrinsic to the immune system rather than the result of some extrinsic force affecting the immune system such as radiation, a virus (e.g. AIDS), chemotherapy, etc

3 categories of cancer vaccination in the modern era

Vaccines expressing shared self-antigens up-regulated in tumor (Provenge) + Generic + Can be formulated for maximal DC targeting and DC activation -Requires sufficient differential expression relative to non-dispensable tissue -Potential for higher degree of tolerance "Endogenous" Vaccination - Turn a patient's own tumor into a vaccine (T-Vec) + Can generate responses against pt-specific neoantigens against which tolerance may be less stringent + Versatility in engineering the injected material to enhance immunity to tumor antigens -2 forms of pt variability: tumors available for injection and operator variability -Must convert "tolerizing" microenvironment to "stimulatory" microenvironment "Personalized" Vaccines created for each pt based on their tumor's mutations + Will generate responses against pt-specific neoantigens against which tolerance may be less stringent + Can (theoretically) be formulated for maximal DC targeting and DC activation -Predictive algorithms to predict best antigens from mutations are imperfect -Extremely difficult and cumbersome pt-specific process

Noninfammatory Cell Death: Apoptosis

apoptotic cells can undergo secondary necrosis and trigger immune responses, they must be swiftly removed in a noninflammatory manner - typically by macrophages This is referred to as Efferocytosis Tissue resident macrophages work to clean up apoptotic bodies. If not removed in a timely fashion, they degenerate and release DAMPS and become inflammatory The most dominant eat-me signal is Phosphatidylserine. Constant removal of apoptotic cells results in pro-resolution/anti-inflammatory signals. Failed efferocytosis is emerging as a key mechanism driving the development and progression of chronic inflammatory diseases, including: Atherosclerosis Myocardial Infarction Heart Failure Obesity Diabetes

Atopy

familial disposition towards IgE mediated allergy • "He comes from an atopic family"

Post Transplantation Cyclophosphamide (PTCy)

immunosuppresant drug used in graft transplants for HSCT alloimmune response is driven by clonal expansion If we use immunosuppresants to kill T cells in transplantation can be used to prevent GVHD in patients who receive highly HLA mismatched grafts Do we need to look in the registry? or is it better to look to a closer family member who is half a match and use immunosuppresant drugs.

T cells are primary mediators of

organ transplant rejection Antigens recognized by these T cells •Major determinants of acceptance/rejection (histocompatibility) are alleles in the major histocompatibility complex (MHC) • Minor (still important) determinants of histocompatibility are alleles that result in protein coding differences elsewhere in the genome - leads to slower graft rejection • T cell antigen is actually peptide+MHC - these are not fully distinct

Chronic activation of two pathways can lead to

pathogenic tissue fibrosis -When well ordered, type 1 and type 2 inflammation lead to diminished inflammation of the other eventually. Disruption of normal pathway leads to fibrosis

Tissue-Resident Macrophages

phagocytosis opsonized and non-opsonized pathogens remove apoptotic cells source of autolytic enzymes - lysozyme, collagenase, elastase synthesis of: complement components transferrin cytokines clotting factors fatty acid & cholesterol synthesis iron metabolism antigen processing & presentation • under homeostatic conditions tissue-resident macrophages self renew • for many tissues, with increasing antigen exposure/inflammation, tissue-resident macrophages are replaced by monocyte-derived macrophages

Food Allergy - Treatment

• AVOIDANCE! • Even minute exposures can cause severe reactions • Much more complex than it sounds due to: • Confusing terminology on ingredient labels • Substantial risk of cross-contamination, especially in food from restaurants, bakeries, etc • Widespread use of many food allergens • Must provide detailed educational materials • Treatment of reactions: consistent availability of selfinjectable epinephrine is key

Common Variable Immunodeficiency (CVID)

• Clinical syndrome - Wide heterogeneity of etiology and phenotype - Onset at any age, but usually in adulthood - Diagnosis not always clear-cut • Diagnostic criteria: - IgG level << 2 s.d. below normal for age - IgA or IgM < normal range for age - Impaired antibody responses - Other causes of hypogammaglobulinemia excluded • Treatment with monthly infusions of IVIG Causes of Acquired Antibody Deficiency in Adults • Common variable immunodeficiency • Adverse effect of drugs - Rituximab - Anti-convulsants (especially phenytoin, valproate) - Long term, high dose corticosteroids • Lymphoreticular malignancies • Late presentation of primary immunodeficiency disease - X-linked agammglobulinemia

Inhibitors of TCR-mediated intracellular signal transduction: Cyclosporine A

• CsA is a fungal metabolite; it is a very hydrophobic cyclic peptide. • It has been used as a frontline therapy to prevent rejection. Made routine organ transplant possible. • Mechanism of Action. Similar to FK506 (see below). • Administration: both IV and oral. A recent formulation by Novartis has made the oral administration more popular. • Pharmacokinetics: Peak plasma level reached within a few hours. Over 50% of the drug is sequestered in red blood cells, which serve as a reservoir for the drug. • Metabolism: CsA is extensively metabolized in the liver by the cytochrom P450 A3 system to over 30 different metabolites. CsA and its metabolites are mainly excreted through the bile into the feces with a small fraction excreted into urine. • Therapeutic use: CsA is the agent that changed the practice of organ transplantation. • Toxicity: Mainly nephrotoxicity. The toxicity has been shown to be caused by the same molecular mechanism as immunosuppression. This is inevitable

The Diagnosis of Food Allergy

• Detailed history • History may be diagnostic with some acute reactions but overall will be verified only 30 - 40% of the time with further testing (especially in atopic dermatitis and GI syndromes) Tests should not be interpreted as just positive or negative but rather as the probability of indicating true food allergy

Inhibitors of TCR-mediated intracellular signal transduction: FK506 (Tacrolimus)

• FK506 is a polyketide of bacterial origin. It is an intellectual offspring of CsA in that it is discovered using a bioassay established by the use of CsA. • FK506 is more potent than CsA (more than 10 fold higher in potency and toxicity). • Administration: both IV and oral. • Pharmacokinetics: Peak plasma level reached within a few hours, similar to CsA. • Metabolism: FK506 is also extensively metabolized in the liver. • Therapeutic use: FK506 is an alternative and sometimes complementary option for organ transplant patients. It has been most widely used in liver transplants, due in part to the unexpected stimulatory effect of the drug on hepatocyte growth. • Toxicity: Nephrotoxicity similar to CsA.

Conditions for GVHD

• Graft must contain sufficient number of immunocompetent donor cells • Host must have transplantation Ags not present in donor • Host must be incapable of rejecting donor cells • GVHD setting: • Transfer of genetically disparate donor T cells into a host incapable of rejection Risk Factors for GVHD • Degree of HLA mismatch • 35% -50% incidence with HLA-matched identical and unrelated donor, respectively. •Stem cell source •Patient age •Sex Mismatch •Conditioning regimen •Post-HSCT infections, particularly CMV The more mismatches you have in HLA loci, the higher chance of developing GVHD

HLA matching and donor selection for HSCT

• Histocompatibility - Matching at the class I and II molecules. • ABO compatibility - Both Rh compatibility and ABO compatibility are not essential for hematopoietic stem cell transplantation • Cross-matching - Recipient serum is examined for preformed donorspecific antibodies (DSA)

Dupilumab (Dupixent)

• Human monoclonal antibody against IL-4 receptor alpha that inhibits signaling of both IL-4 and IL-13. • Approved by the FDA for adults with moderate-tosevere atopic dermatitis, asthma, and chronic rhinosinusitis with nasal polyps that are not adequately controlled with standard therapies.

Group 2 Innate Lymphoid Cells (ILC2)

• ILCs are a family of hematopoietic effector cells which are heterogeneous in location, cytokine production, and effector function. • ILC2s do not express receptors for IgE or antigen. Thought to amplify the Type 2 immune response by producing Type 2 cytokines and mediators which can activate, recruit, or support additional cells.

Chronic Granulomatous Disease

• Impairment of phagocytic cell function • Susceptibility to infection by a limited number of bacteria and fungi with no apparent common features • Unless treated, usually fatal within the first decade of life Male dominant; presents early in life This disease (or syndrome) is the consequences of a number of different defects in an important metabolic pathway (see below). Some are inherited as X-linked recessive traits and some as autosomal recessive traits. The defect common to patients with chronic granulomatous disease is that their phagocytic cells lack the metabolic machinery to produce peroxide (or other forms of reduced molecular oxygen such as superoxide, etc) in response to the ingestion of microorganisms. Formation of granulomas seen on histology Treatment: • Prophylactic antibiotics - Anti-bacterial - Anti-fungal • Interferon-gamma • White blood cell transfusions • Bone marrow transplantation

Haploidentical HSCT with PTC

• Markedly expands donor availability especially for minorities - Almost everyone now has a transplant option • Shortens time to find a suitable donor • Major financial benefit-relevance for the underdeveloped countries • Expansion of PTCy application to other HLAmismatched transplants and strategies barriers to GVHD are now cancer related

Basophils: Key cells in the allergic response

• Release preformed mediators (<15 minutes) that cause symptoms of immediate allergic reactions (histamine) • Produce and release the lipid-derived mediator leukotriene C4 (responsible for late allergic reactions) ~10-30 minutes after activation via the arachidonic acid pathway • Produce and release cytokines and chemokines (minutes to days) following IgE-dependent and IgE-independent activation

The "Allo Paradox"

• Routinely, T cells do not recognize a virus presented on a non-self MHC molecule. How then does a T cell recognize an alloantigen? • Remember from Memory lecture: Only about 1 in 105-106 naïve T cells are specific for a particular peptide/MHC complex. Alloreactive cells are crossreactive 1.The structure of the allo-MHC molecule, in and of itself, is necessary and sufficient to interact with TCR and activate alloreactive T cells -the alphabeta TCR has an intrinsic affinity for MHC molecules, therefore there will be some binding to a broad range of MHC molecules (for example, 2 alleles of class I might differ by just a couple amino acids) 2.The peptides presented by the allo-MHC molecule are recognized by TCR to certain extents -host T cells have not been negatively selected for graft/donor MHC molecules with self(donor) peptides(so many self peptides that one or more of them + different surface will end up compensating enough for tight binding that in the thymus would have been deleted).

Severe Combined Immunodeficiency

• Severe impairment of humoral and cell-mediated immune function -A severe deficiency of both T and B cell function • Susceptibility to infection by virtually any microbe • Untreated, usually fatal within the first year of life • Male predominance (75% male) • Onset of symptoms 2.7 months • Death 6.8 months • Illnesses -pneumonia -diarrhea Pathogens • Bacteria - Gram positive and gram negative - Intracellular and extracellular • Viruses • Fungi • Protozoa • Organisms from all above groups not usually thought to cause disease (opportunistic pathogens) Absolute lymph count very low Deoxyadenosine and deoxyinosine are all toxic to lymphocytes. Loss of ADA can lead to SCID.

Innate lymphoid cell development & lineage commitment

•RAG-independent development in BM •seed barrier & other tissues from fetal liver •self renewing, tissue adapted •lineage negative - no antigen receptors •respond to cues from the local environment ILC innate cells are using the same transcription factors as the Th1, 2 and 17 cells.

Inhibitors of MHC/peptide-TCR interaction

Antithymocyte Globulin • Produced in animals (horse, rabbit, sheep or goat) using human thymocytes as antigens. • Administered intravenously with a half live of 3-9 days. • Used to prevent acute rejections. • Major side effects including serum sickness and nephritis caused by immune response to the animal antibodies. Anti-CD3 antibodies (Orthoclone OKT3) • Some are humanized to prevent immune response to the antibodies themselves. • Administration of anti-CD3 antibodies not only prevents T cell activation by MHC-peptide complex, but also leads to rapid depletion of circulating T cells. • Anti-CD3 antibodies also act as agonists of TCR, leading to secretion of cytokines which is responsible for the side effects. • Toxicity include "cytokine release syndrome" manifested as mild flu-like illness and more severe shock-like reaction that can be lethal.