Hapten-carrier relationships.

The ability of guinea pigs to recognize poly-I,-lysine (PLL), and hapten conjugates of PLL (H-PLL) as antigens is under the control of a single autosomal dominant gene which we will refer to as the PLL gene (1-3). Responder animals carrying this gene form specific antihapten antibodies and display delayed hypersensitivity reactions after immunization with H-PLL conjugates such as 2,4-dinitrophenyl-PLL (DNP-PLL); guinea pigs lacking the PLL gene are incapable of an immune response to DNP-PLL but can nevertheless recognize this conjugate as a hapten. Thus, immunization with DNP-PLL complexed with a negatively charged foreign albumin elicits the formation of high levels of anti-DNP-PLL antibodies in genetic nonresponder guinea pigs (4). Two interesting observations were made concerning the response of these guinea pigs: (a) only an antigenic foreign albumin could act as a carrier for DNP-PLL and stimulate the production of high concentrations of anti-DNP-PLL antibodies in guinea pigs lacking the PLL gene; guinea pig albumin was only marginally effective in this capacity; and (b) nonresponder guinea pigs immunized with DNP-PLL complexed with ovalbumin or bovine serum albumin did not show delayed hypersensitivity reactions to DNP-PLL in spite of the production of high levels of anti-DNP-PLL antibodies. This finding demonstrates the haptenic behavior of DNP-PLL in nonresponder guinea pigs as it has been well established that haptens are incapable of eliciting delayed hypersensitivity reactions (5-10). The process controlled by the PLL gene in the immune response to hapten-P L L conjugates is unknown. Knowledge of the mechanism which allows an immunogenic carrier to elicit an immune response in a genetic nonresponder to the D N P-P L L hapten which it bears should eventually lead to a more complete understanding of the requirements for antigenicity and should also clarify the function of the PLL gene product. This system offers several distinct advantages over other, more complex, antigenic systems because first, the hapten P L L conjugate can behave either as a complete antigen or as a