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What is MHC II is associated with:- and explain in detail?
During antigen recognition, CD4 molecules bind to class II MHC molecules that are displaying antigen (Fig. 6-5), and CD8 molecules bind to class I MHC molecules, and the CD4 or CD8 coreceptor initiates signals that are necessary for activation of the T cells. Because of this requirement for coreceptors, CD4+ helper T cells can recognize and respond to antigen displayed only by class II MHC molecules, whereas CD8+ cytotoxic T cells recognize cell-bound antigens only in association with class I MHC molecules; this segregation is described later. Integrins are adhesion molecules that promote the attachment of T-cells to APCs. To respond, T cells have to recognize not only antigen- MHC complexes but additional signals (CD 28) provided by antigen- presenting cells.