True about MHC class II

Ref Robbins 7/e p203; 9/e p194-195 The main function of major histocompatibility complex (MHC) class IImolecules is to present processed antigens, which are derived primarily from exogenous sources, to CD4(+) T-lymphocytes. MHC class II molecules thereby are critical for the initiation of the antigen-specific immune response.