Immunology test 3

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Biol434Ch.5figures.pptx

T-cell co-receptors: The structures of the CD4 and CD8 glycoproteins.

Comparison of the T-cell receptor with an IgG antibody.

Two types of T cells defined by their receptors

The α:β T-cell receptor (left panel) and the γ:δ T-cell receptor (right panel) have similar structures, but they are encoded by different sets of rearranging gene segments and have different functions.

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The top and bottom rows of the figure show the germline arrangement of the variable (V), diversity (D), joining (J), and constant (C) gene segments at the T-cell receptor α-chain and β-chain loci. During T-cell development, a V-region sequence for each chain is assembled by DNA recombination. For the α chain (top), a Vα gene segment rearranges to a Jα gene segment to create a functional exon encoding the V domain. For the β chain (bottom), rearrangement of a Vβ, a Dβ, and a Jβ gene segment creates the functional V-domain exon. The assembled genes are transcribed and spliced to produce mRNA (not shown) encoding the α and β chains. Exons encoding the membrane-spanning regions are not shown. L, leader sequence.

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T-cell receptor complex

The functional antigen receptor on the surface of T cells is composed of eight polypeptides and is called the T-cell receptor complex.

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a cytotoxic CD8 T cell makes contact with a virus-infected cell, recognizes that it is infected, and kills it. Middle panels: a CD4 helper T cell contacts a macrophage that is engaged in the phagocytosis of bacteria and secretes cytokines that increase the microbicidal power of the macrophage and its secretion of inflammatory cytokines. Bottom panels: a CD4 helper T cell contacts a B cell that is binding its specific antigen and secretes cytokines that cause the B cell to differentiate into an antibody-secreting plasma cell.

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Antigen processing and presentation

What is MHC?

The two types of MHC molecule.

Tissue distribution of MHC molecules.

Processing of antigens for presentation by MHC class II or MHC class I molecules occurs in different cellular compartments.

MHC class I molecules bind to CD8, and MHC class II molecules bind to CD4.

Tissue distribution of MHC molecules.

Processing of antigens for presentation by MHC class II or MHC class I molecules occurs in different cellular compartments.

MHC class I molecules bind to CD8, and MHC class II molecules bind to CD4.

The major histocompatibility complex is divided into three regions containing different types of gene.

Human MHC class I and II isotypes differ in function and in the extent of their polymorphism.

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