Antigen processing is an immunological procedure that gets ready antigens for introduction to unique cells of the immune system called T lymphocytes. It is viewed as a phase of antigen introduction pathways. This procedure includes two particular pathways for handling of antigens from a creature's own (self) proteins or intracellular pathogens (for example infections), or from phagocytosed pathogens (for example microorganisms); consequent introduction of these antigens on class I or class II significant histocompatibility complex (MHC) atoms is subject to which pathway is utilized. Both MHC class I and II are required to tie antigen before they are steadily communicated on a cell surface. MHC I antigen introduction ordinarily (thinking about cross-introduction) includes the endogenous pathway of antigen preparing, and MHC II antigen introduction includes the exogenous pathway of antigen handling. Cross-introduction includes portions of the exogenous and the endogenous pathways at the end of the day includes the last part of the endogenous pathway (for example proteolysis of antigens for authoritative to MHC I particles).