Rabbit lymphocyte populations responding to haptenic and carrier determinants for DNA synthesis

Mesenteric lymph node cells from rabbits primed with dinitrophenyl derivative of either Ascaris extract (DNP Asc) or ragweed fraction D (DNP Rag) were stimulated by the priming antigen, free homologous carrier, or with the hapten conjugated with rabbit serum albumin (DNP RSA), and increase in DNA synthesis was observed by ³H thymidine incorporation. The results showed that both free carrier and DNP RSA stimulated DNA synthesis. The response of the primed lymph node cells to DNP homologous conjugate was slightly higher than that to free carrier, but the optimal concentration of both antigens for maximal thymidine incorporation was 10 to 100 μg/ml. This concentration was about 100 times higher than the optimal concentration of the same antigens for maximal antibody response in vitro. The DNA synthetic response to DNP RSA was much less than that obtained by free carrier, and the optimal concentration of DNP RSA for the response was comparable to the concentration of DNP homologous carrier conjugate to induce maximal anti DNP antibody response. The relative importance of immunoglobulin bearing (B) cells and T cells in the DNA synthetic responses was assessed by fractionating lymph node cells with antigen coated or anti immunoglobulin coated cellular immunosorbent. The results indicated that hapten specific, immunoglobulin bearing cells (B cells) are responsible for the DNA synthetic response to DNP RSA, whereas B cells play a minimal role in the response to free carrier.