Overview In order to initiate an immune response antigen must be recognized. Antigen recognition depends on detection of antigen by special receptors. Antigen recognition depends on cellular cooperation. Cellular cooperation is controlled by recognition of MHC-encoded receptors. Overview ◼ In order to initiate an immune response antigen must be recognized. ◼ Antigen recognition depends on detection of antigen by special receptors. ◼ Antigen recognition depends on cellular cooperation. ◼ Cellular cooperation is controlled by recognition of MHC-encoded receptors