micro module 3

The immune system has 4 types of leukocyte

1). Granulocytes 2). Mononuclear phagocytes 3). Dendritic cells 4). Lymphocytes

Host defenses and the immune system:

1). first line of defense 2). second line of defense 3). third line of defense

T-independent cells

-Activate B cells without T helper cells, alot of repeating units such as lipopolysaccharide bind to B cells that they know the cells needs to die.

natural immunity include:

-Active immunity: a consequence of infection -Passive immunity: child gets immunity from mother before (from bloodstream to the fetus) or after birth (nursing). The baby just receives antibodies, eventually it wears off and immunity is no longer present.

the complement system is activated by

-Alternative pathway; triggered when C3b binds to foreign cell surfaces -Lectin pathway; pattern recognition molecules bind to mannose of microbial cells (MBL) -classical pathway; activated by antibodies bound to antigen, which interact with complement system *any 3 different input can lead to any of the 3 outputs -cascade (each reaction activates the next)

Immunological tests look for the presence of antibody or antigen

-Antibodies used as reagents in tests: -Diagnostics for human, animal and plant health -detection of microbes in food, environment, and etc -Tests for detection of chemical compounds (take blood out of the warm blooded organism and check it out) -Traditionally, immunological tests were called serology, tests used blood serum (polyclonal antibodies)

Functions of Natural killer (NK) cells

-Antibody-dependent cellular cytotoxicity (ADCC): induces apoptosis in self-cells that are infected. Any normal cells covered with antibodies, natural killer would induce apoptosis. -Identifies cells without MCH 1 (naked) cells and also induces apoptosis

Antigens=antibody generator

-Antigens describes a molecule that reacts specifically with antibody, a B-cell receptor, or a T-cell receptor -antigens elicits immune response. and has great varitiey of antigens such as microbes and pollen -General categories include T-dependent and T-independent cells.

Lymphocytes: responsible for adaptive immunity

-B and T cells are highly specific in recognition of antigen. B and T cells generally reside in lymph nodes or lymphatic tissue -Natural killer (NK); cells destroy certain cell types

Antigen receptors on lymphocytes

-B and T cells have membrane-bounded receptors, both have receptors that are stuck into the membrane. -Both have the function to recognize specific antigens -BCR is specific, antibody B cell is programed to make. Every lineage has 1 particular receptor with a binding site that will bind 1 particular antigen. Every B cells has 1 particular type of very specific B-cell receptor each have discrete antigen binding site which will bind the same exact antigen and they can take that antigen, process. it and display it to the T-cell -TCR doesn't recognize free antigen, just float around, it must be presented by other cells

Receptors on B and T cells recognize specific antigens

-B cell receptors are similar to antibodies that they make Y shaped, has 2 binding sites -T cells have only 1 antigen binding site

B-cell activation: the job of T helper cells

-B cells binds to an antigen -B cell presents antigen to T helper cells -T helper cells and B cell interact via MCH 2 and CD4 -T helper stimulates B cell -B cell clone expands to produce memory cells and plasma cells -plasma cells excrete antibodies

Functions of T helper cells

-B cells bring in antigen and proceed it into MHC -Helper cell interacts with MHC to make sure it is 2. CD4 from the T helper cell checks to make sure it is MHC 2 -Helper cells inspects antigen -if recognized, helper T cells activates the B cells

T-dependent cells

-B cells requires confirmation from T helper cell to be activated then goes on to make plasma cells and memory cells

Overview:

-B cells surveillance of tissue: B cells brings antigens into the cells, display antigen to helper T cells, proliferate and differentiate into plasma cells. -Dendritic cells activates T cells -T helper cells: recognize the display from B cells and activate B cells, T helper cells can also activate macrophages -Cytotoxic cells: identify infected self-cell, if the cell is infected induce apoptosis -Specific or adaptive immunity is characterized by highly selective and memory. Highly selective is only being effective against a single pathogen. Memory is rapid response when pathogen attacks again, it can last for months or years.

Clonal selection and expansion of lymphocytes (important for B and T cell)

-Billions of different B cells and T cells. each interacts with a single epitope -Pathogens have multiple epitope, could be in flagella or cell membrane -lymphocytes that keep recognizing epitope keep responding, progeny leave lymphoid organs (not until the antigen is gone) -plasma cells produce antibodies -lymphocyte specificity remains for the cell's life and it's descendants (clone). it never changes specificity once DNA is modified as a hemopoietic cell.

Process of phagocytosis; phagocytes engulf and digest materials and pathogen

-Chemotaxis; there is a recruitment of phagocytes by chemoattractants. Microbe production, phospholipids from injured cells, chemokines, and C5a -Recognition and attachment; direct methods include receptors binding to mannose, indirect methods include binding to opsonins -Engulfment; pseudopods surround the ingested material, and form phagosome -Phagosome maturation and phagolysosome formation; endosomes fuse, lower pH, lysosome bring digestive enzymes -Destruction and digestion; toxic ROS and nitric oxide is produced, pH decreases; enzymes degrade, defensins damage membrane invader, lactoferrin ties up iron. -Exocytosis; vesicles fuse with cytoplasmic membrane, remains are expelled

inflammation cont.

-DAMPS: damage associated molecular patterns, noninfectious inflammatory response. Usually cytosolic or nuclear proteins that leave cell following tissue injury. -migrating neutrophils adhere to capillary walls, migrate into tissue, neutralize or contain microorganisms. -swelling, pain, and vascular dilation. -neutrophils arrive first, are phagocytic, release compounds, short lived and die off quickly, results in pus buildup

Binding site on B and T receptors are the product of randomly spliced gene fragments.

-DNA for constant region never changes -Variable regions gets randomly cut and paste -leads to specificity of binding site

major outcomes of activation

-Inflammatory response: response where C5a attracts phagocytes and C3a with C5a increase blood vessel permeability which leads to mast cells releasing cytokines. -lysis of foreign cells: C5b combines with complement proteins C6, C7, C8, and C9 to form complexes that insert into cell membranes (membrane attack complexes assemble in gram negative cell membranes) -Opsonization is where C3b binds to microbial cells to promote pathogen and promote phagocytosis, functioning as an opsonin. *the inputs can lead to any of all 3 of the outputs

Microbes, killed or inactivated (cannot grow or divide)

-Killed (inactivated) -heat or chemical is used to kill the bacteria -microbe cannot grow and divide in the body -antigenic proteins are still present -body develops immune response to antigen proteins. Exposure to the pathogen results in rapid secondary response.

Nonspecific defenses: genetic defense

-Many pathogens are very host-specific; hosts are often genetically resistant to diseases of other hosts. -Individuals may have varied susceptibility to a given pathogen, due to genetics. -we can breed domesticated animals for improved resistance

Mononuclear phagocytes: develop as they leave the blood stream

-Monocytes; circulate in the blood and cell types develop once they eave the blood stream -Macrophages and dendritic cells differentiate from monocytes. They are named after location where its found in the body.

First line of defenses conti.

-Mucous membrane includes: -GI track and esophagus -mucus -some have cilia -Antimicrobial factors in saliva include: lysozyme, peroxide, lactoferrin. -Lysozyme in tears and other secretions or phagocytes are first line of defense. -Nose removes inhaled particles -throat has mucus and cilia, normal microbiota -acid in the stomach maintains low pH -small intestine has a rapid pH change from stomach to upper intestine -flushing out of urinary tract -pH and normal microbiota of vagina

Pattern recognition receptors (PRRs) includee

-NOD-like receptor (NLRs) are found in cytoplasm. They are floating around. -They detect bacterial components indicating cells has been breached or detect damage. -Response is a series of events to protect host even at the expense of the cell, usually response is apoptosis. -some NLRs join cytoplasmic proteins to form an inflammasome to activate inflammatory response. -NOD-like receptors are found lymphocytes (B, T, and NK cells), macrophages, dendritic cells, and epithelial cells too

When lymphocytes reach the lymph nodes and spleen

-Naive B and T cells become activated when exposed to their specific antigen, activated by T helper cells -Exposure to specific antigen results in clonal selection -activated lymphocytes proliferate and differentiate into effector and memory cells

Antibiotics functions:

-Neutralization: antibodies binding to just enough epitopes on a virus or antigen to make it nonfunctional -Opsonization: Antigen covered antibodies are going to be phagocotyized. -complement system: classic pathway, opsonization by C3b, lysis of formed cells -immobilization and prevention of adherence: multiple antigens bound to each variable region clumps them together making them immobile -cross linking: multiple antigens bound to each variable region clumps them together -Antibody-dependent cellular cytotoxicity (ADCC): any self-cells covered in antibodies are killed by natural killer cells

Phagocyte: cell with the ability to engulf particles, these cells includes

-Neutrophil -Monocyte -Macrophage -Dendritic cells *neutrophil is the first responder, there are alot of these. *monocyte look for bad things in the blood and get rid of it *dendritic cells affects B and T cells

Granulocytes: contains cytoplasmic granules. Identified by dark structures

-Neutrophils; are the highest in numbers. first responders, early to infection. Engulf and destroy bacteria or other material -Basophil; are part of allergic reactions and inflammation. Are similar to mast cells and found in tissues. -Eosinophils: fight parasitic worms. Also involved in allergic reactions

First line of defense contii.

-Normal microbiota defense: (it's essential for the immune system's development) -competitive exclusion of pathogens; cover the binding sites, consume available nutrients -production of toxic compounds; propionibacterium degrade lipids and produce fatty acids (more acidity so it kills other microbes). E.coli synthesizes colicins in the intestinal tract. Lactobacillus in vagina produce low pH, it doesnt let other microbes live. -Disruption of normal microbiota can predispose person to infections (for example, broad antibiotic use); clostridium difficile in the intestine and candida albicans in the vagina.

Where are our pattern recognition receptors (PRR)?

-PRR on the cell surface; they detect microbial components present in the cell's surrounding -PRR in phagosomes and endosomes; they detect components of microbes ingested by the cell. -PRR in the cytoplasm; they detect cell damage as well as microbial components in the cell's cytoplasm

Lymphatic system

-Primary lymphoid organs are the bone and thymus -Hematopoietic stem cells are in the bone marrow. they give rise to all blood cells including lymphocytes. -B cells are made in the bone marrow and matured in the bone marrow -T cells are made in the bone marrow and matured in the Thymus. -once mature, lymphocytes gather in secondary lymphoid organs and wait to encounter antigen.

Memory B-cells provide a rapid secondary response upon re-exposure to an antigen (vaccines work this way), this is not the same as second line of defense.

-Primary response takes 10-14 days for substantial antibody accumulation. Person may be sick, possibly seriously so, although immune system is actively responding. Some activated B cells continue dividing, others differentiate to form antibody-secreting plasma cells. It takes a while for B cells to find the T helper cells, so it just floats around until it finds the right one. Can take awhile.

Pattern recognition receptors (PRRs) includeee

-RIG-like receptors (RLRs) detect viral DNA indicating infection, induce production of interferons. -Interferons alter neighboring cells of viral infection. Interferons are activated by dsRNA to degrade mRNA, stop protein synthesis, or undergo apoptosis. -RIG-like receptors are found in cell cytosol in tissue throughout the body. they are abundant in central nervous system and immune system cells. -they are membrane bound or cytoplasmic -important for phagocytosis, cytokine signaling, and antiviral responses -locations include cell surface to detect from the surroundings. Usually span through membrane to transmit signal to the nucleus. Phagosomes and endosomes to detect from ingested material, compartments are brought in the cell. Cytoplasm to detect from cell damage and microbes in cytoplasm

There are multiple copies of T-cell receptor on each cell surface, just like B cells

-T cell receptor doesnt interact with free antigen, it needs to be displayed -only antigen presented by another cell held in major histocompatibility complex (MHC)

T cells play a different role than B cells

-T cells never produce antibodies -Effector T cell directly interacts with target cells and causes distinct change in it -Cytotoxic T cells are CD8 -Helper T cells are CD4

Adaptive immunity develops throughout life. It starts to diminish throughout life, as you get older. it is most robust when the body is healthiest (in 20s). Adaptive immunity develops the most effective means to eliminate invader.

-Takes a week or more to build following the first exposure. In this time, innate immunity protects but the person may not survive long enough for the adaptive immunity to be active. -Adaptive immunity has memory. Leads to stronger response to re-exposure to same pathogen. Vaccination relies on this ability. -The response has molecular specificity, 1 molecule on the individual pathogen dictates output of that immune response. -Adaptive immunity must distinguish between healthy self and dangerous

Pattern recognition receptors (PRR) include

-Toll-like receptors (TLR); they are anchored in membranes of several cell types. Some in phagosome or endosome membranes to inspect ingested material -cells "see" PAMPs in extracellular environment. Others in phagosomal or endosomal membranes of organelles, characterize ingested material -following detection, signal is transmitted to the nucleus. The signal induces gene expression, inflammatory response, viral surface proteins. -Toll-like receptors are found in macrophages and dendritic cells

Artificial immunity includes:

-Vaccination active: stimulated by exposure to microbial antigen -Artificial passive immunity: patients receives immune serum from another donor.

Vaccination vs immunization

-Vaccination is when a vaccine is administered to you (usually by injection) -Immunization is what happens in your body after you have the vaccine -the vaccine stimulates your immune system so that it can recognize the disease and protect you from future infection -vaccine delivery includes injection, oral, or nasal

Specificity of the adaptive system is determined by lymphocyte receptors and antibodies.

-antibody structure is Y shaped -tips are variable region, they interact with specific antigens, can interact with 2 antigens of the same kind.

T-independent antigens

-can activate B cells without aid of T helper cells -molecules with numerous identical evenly spaced epitopes (polysaccharide) are bound by clusters of B cell receptors -LPS is another T-independent antigen

Component of the immune system involves:

-circulatory system -lymphatic system: blood plasma, concentrated with additional white blood cells, no red blood cells -body tissues -extracellular fluid *cells that carry out immune functions are white blood cells (leukocyte). they have a diverse functions. -Antibodies are principle output of adaptive immune system -Cytokines are chemicals regulating immune functions.

Subunit vaccine

-collects individual proteins and injects those on spikes and cell surface -collect genes and incorporate into safer microbe, host microbe produces proteins -this is the safest but least effective -subunit vaccines are often produced in recombinant organisms such as E.coli expressing gene for virus antigen

issues in immunization

-complications and safety: no vaccine is 100% safe. Rate of adverse reaction is very low -there has been an increase in choice not to vaccinate, it breaks down the herd immunity -vaccine development: economics, expensive to produce and distribute. and availability for developing world

Phagocytosis is to defend the body via ingestion of pathogen by leukocytes

-first observed by llya Mechnikov, he won a nobel prize in 1908 -Chemotactic migration of phagocytes -digestion in phagolysosomes -in innate response phagocytes recognize pathogen-associated molecular patterns (PAMPs)

Functions of T c cells (cytotoxic T cells; CD8)

-for normal cells; all nucleated cells present peptides from cytoplasmic proteins on MHC class 1 molecules, Tc cells do not recognize peptides presented by healthy self cell -for viral cells: virally infected "self" cells present viral peptides on MHC class 1 molecules. Tc cell recognizes viral peptide presented by an infected "self" cell and intiates apoptosis in that target. it also releases cytokines that alert neighboring cells. Target cell undergoes apoptosis.

Microbes, live (attenuated) -vaccines contains live microbe?

-genetically remove portions that are virulent -microbes are alive, they grow and divide -leads to more robust response -most effective which also has a higher risk of causing infection

Dendritic cell function

-goes into tissue and secondary lymphoid organs -collects pathogenic or normal self protein components. Dendritic cells interact with cytotoxic and helper T cells, they express both MHC 1 and MHC2. -Naive T cells that recognize antigen presented by dendritic cells expressing co-stimulatory molecules can become activated. they are activated T cells and can proliferate and differentiate. -Naive T cells that recognize antigen presented by dendritic cells are not expressing co-stimulatory molecules become anergic, anergic T cells cannot responde and undergo apoptosis. -Dendritc cells presenting "self" peptides or other harmless material do not produce co-stimulatory molecules.

Second line of defense is the innate or nonspecific immunity.

-has no function in memory, doesn't remember microbes -Same action regardless of number of exposures, it's based on pattern recognition. Viruses has protein coat and double stranded RNA. Fungus has cell wall based on Chitin. Bacteria has flagella. The recognition are very broad. -Phagocytosis is a key role in engulfment; neutrophil, monocytes, macrophages, dendritic cells -inflammation is very important, 2nd line of defense. -chemical defenses include interferon (antiviral) and complement (lots of roles)

Lymphocytes change as they encounter antigen

-immature lymphocyte: lack fully developed antigen specific receptors -Naive lymphocytes: Have receptors but have not yet encountered approproiate antigen (The DNA chopping causes Naive lymphocytes) -Activated lymphocytes: have bounded to antigen and received confirmation, are able to proliferate -Effector lymphocytes: are descendants of activated lymphocytes such as plasma cells, Tc cells, Th cells -memory lymphocyte: are long-lived descendants of activated lymphocytes; responsible for rapid secondary response if antigen encountered again.

Herd immunity: collective immunity through mass immunization leading to indirect protection for nonimmune individuals. (basically, if a lot of people are vaccinated then you are indirectly protecting the people who arent from spreading the disease)

-immune individuals will not be carriers -collective immunity through mass immunization confers indirect protection on non-immune members of the group -herd immunity is important fro preventing epidemics

Macrophages

-macrophages engulfs material -macrophages degrades proteins into phagosome into peptide fragments -peptide fragments are presented by MCH 2 molecules, epitope -T helper cell recognizes a presented peptide and responds by activating the macrophage. It also releases cytokines that stimulates macrophages to further engulf

preventable vaccines throughout the world

-measles (most preventable) -whopping cough -Rubella -Mumps -others -polio

B cell maturation

-negative selection of self-reactive B cells (B cells undergo alot of negative selection in the bone marrow) -B cells are exposed to "self" in the bone marrow; if bind, induced to undergo apoptosis -the negative selection removes most greater than 90% of B cells; it's critical for preventing immune system from attacking body. in the bone marrow, you need to challenge those B cells to self molecules so you dont get an autoimmune disease

Opsonization

-opsonin proteins bind to microbes and label them for phagocytosis. It enhances phagocytosis, phagocytes have receptors for the opsonins. Opsonins include C3b proteins and antibodies

Another method of vaccine production in transgenic plants is bacteria insertion process.

-pathogenic gene from human is inserted into a bacterium that infects plants -bacteria infects the plants (ex: potato leaves) -Leaf segments sprout into whole plants carrying gene from human pathogen -immune response is triggered from eating the raw plant.

Diapedesis: process of blood cells passing through capillary walls.

-phagocytosis is based on PAMPS or opsonin recognition. -C3b protein or antibodies -cytokines produced trigger aspects of specific immunity

First line of defenses cont.

-physical barriers of the body's order: -skin: the visible layer is the epidermal layer, it is hard for microbes to penetrate, it has salty residue. There is a basement membrane cells, they migrate up. outer layer is dead cells filled with keratin. Epidermis has many layers of epithelial cells. Dermis is tightly woven fibrous connective tissue. Normal microbiota can prevent pathogenic microbes.

Before vaccines, parents in the U.S could expect that each year

-polio would paralyze 10,000 children -german measles (Rubella) would cause birth defects in 20,000 newborns -measles would infect 4 million children, killing 3,000 -Diphtheria would be on of the most common causes of death in school-ages children -pertussis (whooping cough) would kill thousands of infant

T cells maturation

-positive and negative selection of T cells -Positive selection: T cells must recognize MHC and costimulatory proteins, or they are eliminated (having co-stimulatory protein) -Negative selection: T cells also eliminated if recognize "self" peptieds presented on MHC molecules (without co-stimulatory proteins) -more than 95% of developing T cells undergo apoptosis

Complement system: complements activities of the immune system, series of blood circulating proteins, C1-C9, part of innate immune system but can be brought into action by adaptive immune system.

-proteins circulating in blood -system of several blood proteins that interact in a cascade (sequence of biochemical reactions, each reaction activates the next reaction) -proteins named in order it was discovered; C1 through C9, can split into fragments, for example, C3 splits to C3a and C3b -activated by 3 different pathways. Any 3 input can lead to any of the 3 outputs -produces inflammatory cytokines -produces antimicrobial complexes of complement proteins -leads to opsinization

Inflammation

-redness (vascular dilation), warmth, swelling, pain -response to tissue damage caused by infection or injury -mobilize and attract immune components to site of damge -repair tissue damage and eliminate harmful substances -destroy microbes and block infection -pro-inflammatory cytokines can cause fever

Antigens

-response to antigens varies: proteins generally elicit stronger response usually, lipids elicit weaker response usually. Small molecules are usually not immunogenic. -Epitopes are distinct region that is recognized, bacteria carry multitude of different epitopes. They are protein of 5-6 amino acids folded up. Epitopes arent found in your own body. B cell binds to antigen, gets it inside chews it up and displays on the surface, T helper cells recognize it and activate B cells. B cells can now make antibodies, then those antibodies can go back and find the exact epitope that originally B cell receptor had

Dendritic cells: Engulf material and bring it to other adaptive immune system cells for inspection.

-sentinel cells, function as "scouts" (they patrol) -dendritic cells are from monocytes

Vaccine production in transgenic plants

-several in the development -used as freeze-dried plant extract in capsules; no need for refrigeration, inexpensive, it has potential big impact in developing countries *You insert a desirable stretch of DNA sequence into plant cells, and then proliferate it using plant tissue technique.

Cell communication leads to a coordinated response

-surface receptors; serve as "eyes" and "ears" of the cell. Usually span membrane, connect outside to inside. Binding to specific ligand induces response. -Adhesion molecules: Allows cells to adhere to phagocytic cells. Example, endothelial cells can adhere to phagocytic cells allowing them to exit the bloodstream, which slows down. -Cytokines are "voices" of the cell: Cytokines diffuse to other cells and bind to appropriate receptor to induce change. Cytokines are produced by cells, diffuse to others, bind to appropriate receptors to induce changes: growth, differentiation movement, cell death. Act at low concentration, effects local, regional, and systemic. *fever is a byproduct of an infection

Protection via the immune system

-surveillance of the body; different things going around looking for bad stuff -recognition of foreign material -destruction of foreign entities *Immune system must be able to differentiate between self and non-self. Detecting self-cells as bad can lead to autoimmune disorders.

Lymphatic system cont.

-the purpose of the lymphatic system is to bring population of B cells and T cells into contact with antigens, lymphocytes must encounter appropriate antigen (specificity) -This is important because lymphocytes specific to only 1 antigen -lymphocyte must encounter appropriate antigen -fluid from body's circulatory system filters out, not all of the fluid returns back to the capillaries, it enters lymphatics instead. -the lymphatic system contains antigen from tissues and returns it to lymph nodes -Lymph empties back into circulatory system, inflammatory response causes more fluid to enter tissues. This increases antigen containing fluids entering lymphatic system.

Antigens are presented to T cells by major histocompatibility complex molecule (MHC)

-there are 2 types of MHC molecules: -MHC class 1 present endogenous antigens. Found on all nucleated cells. Endogenous antigens, comes from within the cell itself. All nucleated cells have MHC 1 molecules and always display. -MHC class 2 present exogenous antigens: Found on macrophages, dendritic cells, and B lymphocytes (B cells). Exogenous, antigen derivived from outside the cell -T cells recognizes antigen/MHC complex. They identify MHC first and then antigen.

Helper T cells (CD4) recognize antigen presented on MHC class 2 molecules. T h cells respond to exogenous antigens

-to interact, CD4 from the helper cell has to recognize the MHC 2 on B or macrophages cells, then the displayed substance has to know its talking to the right kind of cell, and the very specific receptor can inspect that. If the T helper cell doesn't recognize it keeps bumping until it does. If it does recognize, it says its pathogenic and tells B cells to make more plasma cells.

Pattern recognition receptors (PRRs) recognize pathogen-associated molecular patterns (PAMPs), molecular patterns associated with broad microbe class.

-toll like receptors, NOD-like receptors, RIG-like receptors -May be membrane-bound or cytoplasmic -recognize molecular patterns associated with broad classes of microorganisms -Important in phagocytosis, cytokine signaling, antiviral responses, etc

DNA vaccines

-use nucleotides -pathogen DNA injection into the muscles -some cells uptake the pathogen DNA -Pathogen protein is expressed on host cell surface -immune response stimulated *Pathogen DNA is injected into patient. A few cells take up pathogen DNA and make pathogen protein. Pathogen protein expressed on surface of patient's cells and an immune response is stimulated.

the majority, but not all, of the population needs to be immunized

vaccinations in the US has led to a decrease in diseases -current infant/childhood mortality rate=0.6% -infant/childhood mortality rate 100 years ago=20%

Polio is highly infectious Viral disease

Measles is a serious disease caused by a Virus

Rubella is an infection caused by rubella Virus

Mumps is a Viral disease caused my mumps viruses

Cytotoxic T cells (CD8) recognize antigens on MHC class 1 molecules. T c cells respond to endogenous antigens.

To interact with cytotoxic T cells, first the CD8 of the cytotoxic molecule has to interact with MHC class 1 then the cargo box, displayed on the surface can interact with the specificity of the T cell receptor.

Whooping cough is highly contagious Bacterial disease

Diphtheria (causes lymph nods to swell) is an infection caused by the Bacterium.