Term
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Definition
| Human Leukocyte Alloantigen- discovered in the 1960s to be the same thing as the MHC complex |
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Term
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Definition
| Major Histocompatibility Complex, Closely linked genetic loci on the short arm of chromosome 6 which encode for the alloantigens of major importance in allograft compatibility (MHC = HLA Complex). |
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Term
| List the three Class I HLA proteins |
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Definition
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Term
| List the three Class II HLA proteins |
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Definition
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Term
| What is the role of Class I HLA proteins? |
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Definition
| Presentation of antigen directly to CD8+ T cells |
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Term
| What is the role of Class II HLA proteins? |
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Definition
| Presentation of antigen directly to CD4+ T cells |
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Term
| Define Class III HLA proteins |
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Definition
Soluble antigens including several Complement components, Tumor Necrosis Factor, etc
Not transplantation antigens and not directly involved in immune regulation |
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Term
| List the Class I Accessory HLA proteins |
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Definition
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Term
| List the Class II Accessory HLA proteins |
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Definition
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Term
| What is the role of Class I HLA accessory proteins? |
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Definition
Form ligands for NK cells
(Except HLA-F, function unknown) |
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Term
| What is the role of Class II HLA accessory proteins? |
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Definition
| Regulate peptide loading on HLA-DR, -DP, and -DQ |
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Term
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Definition
| The unit of closely-linked alleles on each chromosome that expresses HLA antigens |
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Term
| Describe how parental haplotypes are expressed |
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Definition
Each individual inherits a maternal haplotype and a paternal haplotype and, because the HLA genes are co-dominant, expresses all of the inherited HLA antigens
Each individual expresses 12 HLA specificities. |
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Term
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Definition
| Determining the HLA antigens possessed by an individual using DNA analysis |
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Term
| What are some uses of HLA typing? |
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Definition
Transplantation — histocompatibility testing
Paternity testing
disease associations
anthropology |
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Term
| What are the odds of sharing both haplotypes with a sibling? |
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Definition
25% (based on Mendelian genetics)
50% chance of sharing just 1 parent haplotype
25% chance of sharing none |
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Term
| What are the odds of sharing haplotypes with an unrelated donor? |
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Definition
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Term
| Where are MHC Class I proteins found? |
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Definition
Surface of all nucleated human cells
(as many as 106 molecules/cell) |
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Term
| What are the principle antigens recognized in allograph rejection? |
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Definition
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Term
| Describe the pathway that Class I MHC proteins take to present immunogens |
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Definition
1. Virus infects cell
2. Viral proteins synthesized in cytoplasm
3. Fragments bind to MHC in ER
4. Transport to cell surface
5. Cytotoxic T cell recognizes complex and kills infected cell |
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Term
| What are the two proteins within the MHC class I complex? |
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Definition
HLA Glycoprotein (MW 44,000)
b2 Microglobulin |
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Term
| How many types of MHC Class I molecules are expressed per individual? |
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Definition
6: 2 each of HLA-A, HLA-B, HLA-C
(one type of each from each parent) |
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Term
| What protein domain of MHC I does CD8 react with? |
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Definition
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Term
| Where are MHC Class II proteins found? |
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Definition
Primarily on the surface of antigen-presenting cells (APC)
Monocytes/macrophages, B cells, dendritic cells |
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Term
| What is the main role of class II MHC? |
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Definition
| Generating helper T cell function that is essential for most immune responses |
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Term
| Describe the protein chains in MHC II |
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Definition
Heterodimer, each with 2 extraceullar, transmembrane, and intracellular segments.
First domain of each chain (a1+b1) form the protein-binding site. |
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Term
| How many types of MHC Class I molecules are expressed in an individual? |
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Definition
6: 2 each of HLA-DP, HLA-DQ, HLA-DR
(one type of each from each parent) |
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Term
| What protein domain of MHC II does CD4 react with? |
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Definition
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Term
| Define antigen presenting cell |
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Definition
Cells that express MHC class II proteins and present antigens to CD4+ T cells.
These are sometimes called “professional APCs" |
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Term
| Are phagocytes more important in primary or secondary immune responses? |
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Definition
| Secondary responses, because opsonized particles are much more efficiently phagocytosed |
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Term
| What is the most important APC in the primary immune response? |
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Definition
| Dendritic cell- it is highly efficient and highly dispersed, motile, and spread throughout the body to present to T cells |
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Term
| Are B cells more important in primary or secondary immune responses? |
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Definition
| Secondary, since they capture specific immunogens then multiply during further exposure |
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Term
| What is the name of the pathway of MHC I presentation? |
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Definition
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Term
| What is the name of the pathway of MHC II presentation? |
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Definition
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Term
| List the steps in the pathway for MHCII to present to helper T cells |
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Definition
1. APC takes up pathogen
2. Pathogen is taken apart
3. Pathogen proteins are cut
4. Peptides bind to MHC and go to cell surface
5. CD4 receptors bind to MHC II |
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Term
| List the steps in the endocytic pathway for B cells to be activated by helper T cells |
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Definition
1. Surface IG bind bacteria
2. Cell engulfs and degrades
3. Peptides bind to MHC II in endocytic vesicles
4. Transport to cell surface
5. Helper T recognizes complex and activates B cell |
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Term
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Definition
| T-cell receptors for the specific complex of a particular peptide bound to a particular MHC molecule. |
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Term
| How is MHC and disease susceptibility related? |
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Definition
There is a statistical association between the susceptibility (or resistance) to some diseases — infectious and especially autoimmune—and the occurrence of HLA alleles.
The association is never 100% and the mechanism(s) of the relationships are unknown. |
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