The role of the major histocompatibility complex in <em>in vitro</em> antibody responses; MHC restriction in responses involving linked recognition of antigenic determinants is not solely consequent to T cell-accessory cell restrictions.

Major histocompatibility complex (MHC) restrictions in the secondary antibody response in vitro to the soluble protein antigen trinitrophenyl keyhole limpet haemocyanin (TNP-KLH) were investigated in this study. Experimental conditions were employed which ensured that co-operation between KLH-primed T cells and TNP-primed B cells was possible only through linked recognition of carrier and haptenic determinants. Under such conditions co-operation between T and B cells appears to be MHC-restricted.