Differentiate between T H and T C cells. The antigen binding site is formed by the interaction of variable regions of heavy and light chains. Each class of immunoglobulin has different structural and functional characteristics. Section 20.6 T cell receptors are antigen-specific proteins found on the surface of T cells. They are structurally and evolutionarily related to immunoglobulins.
T cells recognize antigen only in the context of other proteins found on cell surfaces.
Section 20.7 Proteins encoded by the MHC are molecular reference markers that permit T cells to interact with antigen. Found on the surfaces of APCs and target cells, MHC proteins embed processed antigen, and present it to T cells. This is the only way T cells can recognize nonself antigens, and initiate the specific immune response. Cytokines are soluble mediators, produced by leukocytes that regulate interactions between cells. Others, such as IFN and TNF, act on a wide variety of cell types.