Immunology Exam 2

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TCR

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disulfide-linked heterodimer of the highly variable a and B chains expressed at the cell membrane as a complex w/the invariant CD3 chains.

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Major histocompatability complex

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cluster of genes on human chromosome 6 or mouse chromosome 17. Encodes a set of membrane glycoproteins caleld the MHC molecules
also encodes proteins involved in AG processing and other aspects of host defense.
Most polymorphic gene cluster in the human genome, having large numbers of alleles at several different loci.

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MHC I

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present antigenic peptides gererated in the cytosol to CD8 T cells.

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MHC II

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present antigenic peptides generated in intracellular vesicles to CD4 T cells.

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beta-2-microglobulin

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the light chain of the MHC class I proteins, binds noncovalently to the heavy or a chain.

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anchor residues

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bind peptide fragments of Ags to specific MHC class I molecules.
residues of the peptide that have AA side chains that bind into pockets lining the peptide-binding groove of the MHC I molecule.
different patterns of anchor residues equal anchor motifs.

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CD4

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cell surface protein important for recognition by the TCR of antigenic peptides bound to MHC II molecs.
acts as a co-receptor by binding to the lateral face of the MHC II molecs

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CD 4 T cells

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T cells that carry the co-receptor protein CD4. They recognize peptides derived from intravesicular sources, which are bound to MHC class II molecules
differentiate into CD4 TH1/TH2 effector cells that activate macrophages and B cell responses to Ag.

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CD8

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cell surface proteinimportant for recog by the TCR of antigenic peptides bound to MHC I molecs.
Acts as a co-receptor by binding to the lateral face of MHC I molecs.

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CD8 T cells

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T cells that carry the co-receptor CD8
Recognize Ags (i.e. Viral Ags) synthesized in the cytoplasm of the cell.
Differentiate into cytotoxic CD8 T cells.

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peptide binding cleft/groove

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longitudinal cleft in the top surface of an MHC molecule into which the antigenic peptide is bound.

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peptide editing

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in the context of AG processing and presentation, the removal of unstably bound peptides from MHC II molecs by HLA-DM.

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HLA

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human leukocyte antigen
genetic designation for the human MHC. individual loci are designated by uppercase letters (i.e. HLA-A) and alleles are designated by numbers (i.e. HLA-A*2102)

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HLA-DM

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invariant protein in humans involved in loading peptides onto MHC II molecs.
Encoded in the MHC w/in a set of genes resembling MHC II genes.
*homologous protein in mice= H-2M

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H-2

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major histocompatibility complex of the mouse.
haplotypes are designated by a lower case superscript, as in H-2(^b)

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HLA-DO

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atypical MHC II molec that acts as a negative regulator of HLA-DM, binding to it and inhibiting the release of CLIP from MHC II molecs in intracellular vesicles.

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haplotype

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linked set of genes associated w/one haploid genome.
used mainly in connection w/the linked genes of the MHC, which are usually inherited as one haplotype from each parent.

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Helper CD4 T cells

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CD4 T cells that stimulate or "help" B cells to make Ab in response to antigenic challenge. Both TH2/TH1 subsets of effector CD4 T cells can carry this fxn.

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Ag presentation

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describes the display of Ag as peptide fragments bound to MHC molecs on the surface of a cell. T cells recognize Ag when it is presented in this way.

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APCs

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antigen-presenting cells
highly specialized cells that can process Ags and display their peptide frags on the cell surface w/other co-stimulatory proteins required for activating.
mainly dendritic cells, macrophages, B cells.

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antigen processing

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the degradation of proteins into peptides that can bind to MHC molecs for presentation to T cells.
All protein Ags must be processed into peptides before they can be presented by MHC molecs.

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thymic cortex

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outer region of each thymic lobule in which thymic progenitor cells proliferate, rearrange their TCR genes, and undergo thymic selection, especially positive selection on thymic cortical epithelial cells.

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thymic cortical epithelial cells

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rearrange their TCR receptor genesand undergo thymic selection, especially positive selection.

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thymic stroma

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epithelial cells and connective tissue that form the essential microenvironment for T cell development.

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thymocytes

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lymphoid cells found in the thymus.
consist mainly of developing T cell, although a few have achieved fxnl maturity.

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thymus

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site of T cell development
a lymphoepithelial organ in the upper middle of the chest, behind the breastbone.