Elements of the Immune System and their Roles in Defense (Immunology)

Humoral immunity

Immunity due to antibodies and their actions.

Mannose receptors and Dectin-1

In lectin family-recognize carbohydrates. C type lectins because calcium involved in binding.

Dendritic cells

In tissues. They have distinct star shaped morphology. Cellular messengers that are send to call adaptive immune response by leaving tissue with cargo of intact degraded pathogens. They take them to lymphoid organs that specialize in making adaptive immune responses.

Lectin Pathway

Induced by infection and requires some time (innate) mannose-binding lectin binds to pathogen surface and is second to act.

What is the adaptive immune system

2nd line of defense.

Eosinophils

2nd most abundant granulocyte. Defends against helminth worms and other intestinal parasites. They do this through release of granule contents.

Macrophage Receptor with Collagenous Structure(MARCO)

Another scavenger receptor that binds gram + and gram - bacteria.

Where do B lympocytes and T lymphocytes originate and mature?

B and T cells both originate in bone marrow. B cells mature in bone marrow and T cells migrate in blood from bone marrow and mature in thymus.

What small granular lymphocytes are responsible for adaptive immune response?

B cells and T cells. The circulate in quiescent and immature state and are functionally inactive. Recognition of pathogen results in lymphocyte selection, growth, and differentiation.

Classical Pathway

C-reactive protein or antibody binds to specific antigen on pathogen surface. Third to act.

What does C3b do? What does C3a do?

C3b tags pathogen for destruction via phagocytosis and formation of protein complexes that damage pathogens membrane. C3a acts a chemoattractant to recruit effector cells from blood to the site of infection.

T-lymphocytes (T-cells)

Cell surface receptors are T-cell receptors, never as soluble proteins.

B-Lympocytes (B-Cells)

Cell surface receptors are immunoglobulins. Effector B cells are plasma cells. Plasma cells secrete soluble forms of immunoglobulins. (antibodies)

Immune System

Collection of cells dedicated to the defense of body against disease.

Chemokine

Cytokine involved in directing WBCs to sites where their functions are needed.

Describe Granulocytes

Cytoplasmic granules, kill microorganisms, enhance inflammation and they are also called polymorphonuclear leukocytes. Some examples of these are neutrophils, eosinophils, and basophils.

What are the two types of T-cells and what do they do?

Cytotoxic T cells kill cells infected with virus or certain bacteria. Nk cells and Tc have similar effector functions except NK are innate and Tc cells are adaptive. Helper T cells secrete cytokines that help other cells become fully activated effector cells. Macrophage more active in phagocytosis. B cells to become plasma cells and regulatory T-cells control activity of other T cells.

What are antimicrobial peptides secreted by macrophage and neutrophils. They cause permeability in pathogen membrane which results in death of pathogen?

Defensins

What is cross reactivity regarding cell receptors?

Different cells express different receptors or combination of receptors.

Paroxysmal nocturnal hemoglobinuria

Disease characterized by episodes of complement mediated lysis of RBC that lack cell surface DAF, HRF, or CD59. Impaired synthesis of tail of proteins is cause.

Natural Killer Cells

Effector cells of innate immunity and function as defense against viral infections by entering infected tissue, kill virus infected cells, secrete cytokines that impede viral replication in infected cells. (Large granular lymphocyte)

True or False: The adaptive is more specific which means there is no need for the innate immune system.

False, most infections are cleared with a combination of the innate and adaptive immune systems. In addition the innate immune system activates the adaptive immune system.

Sebum

Fatty acids and lactic acid. They inhibit bacterial growth on skin.

What does the spleen do?

Filters pathogens out of blood and is filtering out damaged or old rbcs. Also responsible for blood borne pathogens such as insects. They do this by macrophage and dendritic cells in the spleen phagocytize microorganisms. These cells stimulate B and T cells arriving in blood.

Mast cells

Found in all connective tissues. Granules like basophil and its blood borne progenitor unknown. Activation and degranulation of mast cells at infection site major contributor to inflammation. Expulsion of parasites from the body through the release of granules containing histamine and other active agents.

TLR 4

Gram Negative Bacteria release LBP and picks up soluble LPS and delivers it to CD14 or if bacteria is bound to macrophage phagocytic receptors then when LPS is released from the bacteria it can be bound by CD14. CD14 acts as a coreceptor to TLR 4. It interacts with MD2 and forms a complex with CD14 and LPS. This activates TIR domain.

What is asplenia and what kind of mutations cause it? Is it a common condition?

It is when someone is born without a spleen. Deleterious mutations in gene for ribosomal protein SA which is a component of small subunit of ribosome.

Basophils

Least abundant granulocyte. Defends against parasites and extremely rare so not much known about it.

Monocytes

Leukocytes that circulate in the blood. Bigger than granulocytes and have a distinct indented nucleus. Al look the same. Circulating precursor to macrophage.

Extracellular Pathogens

Live and replicate in spaces between human cells. Accessible to soluble secreted molecules.

Edema

Lymph accumulation in tissues that results in swelling.

Draining lymph node

Lymph node nearest site of infection, to which extracellular fluid containing antigen and cells from the infection site is transported. Within lymph node B and T cells with receptors that bind pathogen are stimulated to divide and differentiate into effector cells.

Lymphocyte recirculation

Mature B and T cells move through body in blood and lymph. leave primary lymph tissue where they develop and enter blood. When they reach the capillaries they leave blood and enter lymph node. If not activated it will remain for a short time and then leave via the efferent lymph and eventually return to blood. Exception is spleen where they enter and leave in the blood.

Clonal Selection

Mechanism by which immune response derives only from individual antigen specific lymphocytes which are stimulated by antigen to proliferate and differentiate.

Antigen

Molecule or molecular fragment that is recognized by antibody, or B-cell receptor or T-cell receptor.

Macrophage

Monocytes which travel in blood to tissues. They mature into macrophages and have a "Large phagocyte." They have irregularly shaped cells. Numerous vacuoles with engulfed material. Scavenger cells of the body. Long lived. Warn other cells. 1st to sense invading microorganism. Secrete cytokines that recruit neutrophils and other leukocytes.

Neutrophils

Most abundant granulocyte, capture, engulf and kill microorganisms, effector cells of innate immunity, and are short lived and die at site of infection which is pus.

Clonal Expansion

Multiplication of lymphocytes after activation by antigen.

What are the eight myeloid progenitor cells?

Neutrophil, eosinophil, basophil, macrophage, dendritic cell, mast cell, platelets, and erythrocytes.

Does adaptive immune response against one pathogen provide immunity against another pathogen?

No only one.

Pathogen

Organism that causes disease and include bacteria, viruses, fungi, and parasites.

Scavenger Receptors

Originally observed to scavenge damaged molecules of low density lipoprotein from blood. Later shown to bind wide assortment of negatively charged microbial ligands.

What are lymphatics?

Originate in the connective tissues throughout the body. Collect plasma that leaks out of blood vessels and forms extracellular fluid. Lymph returns to the blood via thoracic duct into left subclavian vein in neck. Not pumped one way valves direct fluid away from peripheral tissues driven by movement.

Describe Megakaryocyte/erythroid progenitor Examples

Permanent residents of bone marrow, giant nucleus, fusion of multiple precursor cells, nuclei have multiple sets of chromosomes. Example: platelets and erythroblasts.

Opsonization

Phenomenon by which a coating of antibody facilitates phagocytes.

What three things make up the innate immune system?

Physical barrier, chemical barrier, and responses ready and waiting for infection. 1st line of defense.

What is the name of a virus family who has a life cycle inside and outside a cell?

Picornavirous.

Immunization

Procedure where severe disease is prevented by prior exposure to the infectious agent in a form that cannot cause disease

Adaptor Protein

Protein that has no enzymatic or other activity itself , but brings together two other components so they can intereact. (MyD88 and TRAF6

What is red pulp? What is white pulp?

Red pulp-RBC monitored and removed. White Pulp-WBC gather and provide adaptive immunity-similar to the lyph node. Main difference is pathogens enter and leave in the blood.

Intracellular Pathogens

Replicate inside human cells and not accessible to soluble secreted molecules. Defense strategy is to kill human cell in which pathogen resides.

Complement proteins?

Soluble proteins made constitutively by liver and present in the blood, lymph, and extracellular fluid.

What are cytokines?

Soluble proteins that interact with other cells and trigger immune response or inflammation. Heat, pain, redness, and swelling. Call cells into area and cause blood capillaries to get larger and cause more blood flow.

Describe how the sites of Hemotopoiesis change

Starts in yolk sac, then switches to liver and spleen. Then shortly before birth switches to bone marrow.

Immunology

Study of physiological mechanisms that humans and other animals use to defend their bodies from invasion by other organisms.

Antigen Receptor

Surface immunoglobulins and T-cell receptors.

What is the name of the signaling domain in toll-like receptors? Also, what are LRRs?

The signalling domain is Toll-Interleukin-1 receptor. LRRs are pattern recognition domain of TLRs is a repeated sequence motif 20-29 aa residues in leucine and are called leucine-rich repeats.

What are complement proteins in their active form? Inactive form? Which protein is the most important?

They are proteases in their active form and zymogens in their inactive form. Component C3 is the most important.

What do lysozymes do?

They attack peptidoglycan and are in tears and saliva and degrade bacterial cell wall.

What do acid PH do and where are they found?

They deter pathogen growth and are found in the stomach, vagina, and skin.

Complement Fixation

When C3b becomes covalently bound to pathogen.

Alternative Pathway

Works at start of infection. (innate). First to act and pathogen surface creates local environment conductive to complement activation.

Neutralization

antibody binding to pathogen such that it inhibits pathogen growth, replication, or interaction with human cells. The most important function of antibodies is to facilitate engulfment and destruction of extracellular microorganisms and toxins by phagocytes.