Recognition of Infected Cells by Cell Receptors

Discrimination between nonself-derived peptides, i.e., those from a pathogen, and self-derived peptides requires that the chemical interactions between the T cell via its TcR and the MHC protein with its bound peptides be extremely specific. This specificity is a property of the particular TcR of the individual T-cell clone. 

The MHC I protein contains two polypeptide ehains a and p. The a chain contains two distinct domains, a 1 and a2, that are on the outside surface of the antigen-presenting 

Stimulation of B cells to proliferate and differentiate into memory and plasma cells depends on epitope binding to epitope-specific receptors on CD4+ T-helper cells. Transmembrane signaling then requires the coreceptor protein CD3. Binding of the T-cell receptor to the antigen-presenting B cell occurs via the TcR that interacts with 

Presentation of foreign (nonself) peptides by the MHC II protein to Th cells occurs in a similar manner to the MHC I proteins, requiring both the MHC II protein and T-cell surface proteins of the CD3 complex (see Table 35-1). The cell surface protein CD3 is involved in transmembrane signaling and initiation of cytokine (immune system messenger molecules) synthesis. Newly synthesized and recycled MHC II proteins are, like the MHC I proteins, ushered to the surface of the APC. 

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