Adaptive Immune Response

infected, nucleated cell can process and present endogenous antigens to cytotoxic T-lymphocytes via self-MHC-I molecules.

Cell-Mediated Immune Response

happens when a macrophage or dendritic cell endocytosis viral antigens such as killed visions that are then transported from phagosome to the cytoplasm, where antigens enter into the endogenous pathway.

Cross-Presentation

under some circumstances exogenous antigens may enter the endogenous antigen pathway and are presented via MHC-I to CTL.

Cross-Presentation

Which type of Antigen Presenting Cell is considered the "key" APC, or "professional" APC?

Dendritic Cells

produced from bone marrow stem cells; have long, thin cytoplasmic processes.

Dendritic Cells

one of three recorded cancers that can spread like contagious disease, for example through biting.

Devil Facial Tumor Disease

host cells present foreign antigen made within the cytosol of the cell by microbes that have infected the cell; are not found in phagosomes.

Endogenous Antigen Presentation

phagosome fused with lysosome.

Endosome

foreign material is phagocytosed into phagosome, which then lyses with a lysosome and creates endosome; ingested proteins break into peptide fragments of varying length in endosome; endosome containing peptide fragments fuses with others carrying MHC-II molecules; MHC-II molecule presents peptide fragment on cell surface.

Exogenous Antigen Presentation

T/F: Heterozygosity of MHC molecules in an animal is not considered an evolutionary advantage overall.

False

T/F: A given MHC molecule can present many different peptides at one time.

False (Are capable of presenting several different peptides, but only one at a time).

T/F: APCs can take up, process, and present both exogenous and endogenous antigens to cytotoxic T-lymphocytes.

False (Can only present exogenous microbial antigens)

T/F: In any acquired immune response to a pathogen we will see both CMI and Humoral immune responses, however CMI will always dominate.

False (One or the other WILL dominate, but not ALWAYS CMI).

T/F: B-cells can only take up antigen that is unrecognizable to their BCR.

False (can only take up antigens their BCR recognizes).

antigen presenting cells that engulf exogenous antigen can process and present this exogenous antigen via MHC-II molecules to T helper lymphocytes; T helper cells can help B cells to make antibody.

Humoral Immune Response

good at antigen capture.

Immature DC

organized cluster of genes that control antigen presentation.

MHC

the cells in each animal will be able to express a number of different MHC molecules (~200,000 different ones) and thus present a wide variety of antigens to its immune system.

MHC Polymorphism / MHC Allelic Diversity

antigen fragments can only trigger an immune response if they are bound to a self-MHC molecule.

MHC Restriction

determine susceptibility and resistance to disease in which the acquired immune responses have a significant role.

MHC genes

can be expressed by most nucleated cells and present antigenic peptide fragments to cytotoxic T-cells; antigenic peptide fragments derived from endogenous antigens from intracellular organisms (or tumor cell antigens).

MHC-I

can only bind peptides that are 9 amino acids long.

MHC-I Molecules

involved in the processing and presentation of Endogenous antigen by nucleated cells to Cytotoxic T-cells.

MHC-I Molecules

MHC Molecule Classes (2)

MHC-I, MHC-II

only expressed by professional and semi-professional APCs; present antigenic fragments derived from exogenous antigen to T-helper cells.

MHC-II

can bind peptides that are ~20 amino acids long.

MHC-II Molecules

involved in the processing and presentation of Exogenous antigen by APCs to helper T-cells (Th-cells/CD4+ T-cells).

MHC-II Molecules

semi-professional APC that can only present antigen to previously sensitized T-cells; are also phagocytic cells.

Macrophages

Which type(s) of Antigen Presenting Cell is considered "semi-professional"?

Macrophages, B-cells

specialized glycoproteins coded for by genes located in a gene cluster called the Major Histocompatibility Complex.

Major Histocompatibility Complex

virus resulting in nerve paralysis in chickens.

Marek's Disease

best for processing and presenting antigens.

Mature DC

T-cells that have never encountered antigen before.

Naive T-cells

depends on expression of sufficient number of different MHC genes in the population to enable some individual to overcome infection by new pathogen.

Population Survival

associated with person expressing certain MHC class II molecules with binding groove that can bind and present self-antigens of collagen to immune system.

Rheumatoid Arthritis (humans)

have a T-cell Receptor (TCR) on the surface that can recognize antigen only when presented by an APC or an infected, nucleated cell within the context of self-MHC molecules.

T-cells

Example of MHC Restriction

T-cells only recognize antigen in self-MHC molecules.

can only interact with self MHC presenting a particular peptide complex; has unique specificity.

TCR

disease that has caused Tasmanian Devils to lose genetic diversity at the MHC gene site that has wiped out more than half of their population.

Tasmanian Devil Facial Tumor Disease

T/F: APC can present both MHC-I and MHC-II-bound Ag at the same time.

True

T/F: APC can present both exogenous and endogenous Ag at the same time because APC have nuclei.

True

T/F: Dendritic cells are the only APC's that can present and activate naive T-cells, and are therefore essential for initiating primary immune response.

True

T/F: Homogenous MHC genes can lead to the wipe out of a population by exposure of the population to a new pathogen.

True

T/F: MHC genes are very complex and are about the same size as the total genome of the bacterium E. coli.

True

T/F: The MHC molecules an animal can make will determine which antigens can be presented to cells of the immune system.

True

T/F: The antibody the plasma cells make is identical to the antibody bound to the BCR that gave rise to plasma cell.

True

T/F: The more heterozygous an animal is for MHC, the more its MHC molecules can bind greater variety of antigenic peptides.

True

T/F: The only two individuals that would have the same repertoire of MHC genes are genetically identical twins.

True

T/F: B-cells require help from Th-cells to differentiate into an antibody secreting Plasma Cell.

True (get help by taking up, processing and presenting antigen to Th-cell).

region that actually binds antigen on MHC molecules; highly polymorphic and consist of a large number of alleles that code for amino acid sequences in this region.

Variable Region

Dendritic Cells are found in all organs except what? (3)

brain, parts of eye, testes.

What is the importance of Cross-Presentation in immunity to viruses?

cross-presentation of viral antigens can result in the engulfment of dead virions by APC that may then be able to trigger a CTL response; in this case, a cell-mediated CTL response would ultimately be required to kill the virally infected cells, even though the antigen was originally taken up and presented by APC via the exogenous antigen pathway.

What type of antigens can Dendritic Cells take up? (3)

dead microbes, soluble antigens, antigens released by dying cells.

Antigen Presenting Cell Types (3)

dendritic cells, macrophages, B-lymphocytes

Dendritic Cells are prominent where? (3)

lymph nodes, skin, all mucosal surfaces where invading microbes are likely to be encountered.

How much more effective are Dendritic cells at antigen processing than macrophages and B-cells?

>100x

What happens to immature DC's after antigen capture?

migrate to lymph nodes to mature and process Ag to present to lymphocytes.

Components of Exogenous Antigen Processing and Presentation (4)

APCs, MHC-II, T-helper cells, B-cells (make more antibodies)

critical amino acids of the antigen.

Anchor Residues

Components of Endogenous Antigen Processing and Presentation (3)

nucleated infected cells/tumor cells, MHC-I, cytotoxic T-cells.

MHC-I cannot be found where? (4)

on RBCs, gametes, neurons, placental trophoblast cells.

APC Mechanism

processing of microbial antigen, loading of antigen into MHC-II molecule, shuttling of MHC-II-Ag complex to surface for presentation.

present exogenous antigens to T-helper lymphocytes.

Antigen Presenting Cells

Essentials of Adaptive Immune Response (4)

Antigen, antigen presenting cells, MHC molecules, B- and T-lymphocytes

in humans, diseases that are almost always linked to certain MHC alleles/genes.

Autoimmune diseases

have a B-cell Receptor (BCR) on the surface that can recognize/interact with soluble, free in solution antigens.

B-cells

semi-professional APC with the main function of making antibodies; bind antigen with BCR then ingest and process antigen before presenting it via MHC-II molecules to T-helper cells.

B-cells

need help from helper T-lymphocytes to make antibody; make antibody specific for the antigen that the B-cell recognized initially.

B-lymphocytes

Examples of Infectious Disease by MHC genotypes (2)

Bovine Lymphoma and Bovine Leukemia Virus, Marek's Disease

capability of MHC molecule to bind a number of different antigenic peptides.

Broad Specificity