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Review the role of the Major Histocompatibility Complex (MHC). (p.8)
- Nucleated cells have histocompatibility molecules.
- - On cell surface membrane
- - Antigens or glycoproteins
- - Identify cell as belonging to the host
- - Also called HLA = human leukocyte antigens
- Genes that code for MHC (HLA) located on chromosome 6 – area known as major Histocompatibility complex (MHC)
- Important to cellular recognition events
- Immunological activity influenced by antigens
- - Activity of Cytotoxic T Cell
- - Interaction between Macrophage and T Helper Cell
- - Interaction between T Helper Cells and B Cells
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What are Class I antigens?
Where would you find them?
- Found on surface of virtually all nucleated somatic cells and platelets (not on RBCs)
- - Coded by gene loci – HLA-A, HLA-B, -C
- - Bind foreign peptides and present them as foreign antigens to Cytotoxic T cells (CD8 cells)
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What are Class II antigens?
Where would you find them?
- Found on immune cells – macrophages, B-cells, dendritic cells, Langerhan cells of skin, venular endothelial cells
- - Bind to receptors on Helper T cells (CD4 cells)
- - Coded by gene loci – HLA-DR, -DP, -DQ
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What is the role of Class I and Class II antigens in immune response?
Present antigens to the immune system.
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What is an allele?
- Different form or variation of the same gene.
- Base sequence may be difference
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Cell surface membranes of T Cells also contain antigens called clusters of differentiation (CD).
CD4 and CD8 antigens are associated with what cells? (p.11)
- CD4 and CD8 antigens are adhesion glycoproteins, called clusters of differentiation that are expressed on T lymphocytes
- CD8 proteins – expressed on suppressor or cytotoxic T cells
- - Associated with Class I MHC molecules
- CD4 proteins – expressed on helper T cells
- - Associated with Class II MHC molecules
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HIV affects what subset of T cells?
CD4 Helper T cells
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What are criteria (CD4 cell count) for diagnosis of AIDS?
CD4 count < 200 = diagnosis of AIDS
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What cell surface antigens are routinely identified prior to tissue transplantation and why? (p.8)
- Histocompatibility for HLA – HLA-A, HLA-B, HLA-DR
- Class I antigens involved in transplant rejections
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