The Significance of the Protein Carrier in the Stimulation of DNA Synthesis by Hapten-Protein Conjugates in the Secondary Response.

Rabbits were immunized with 2,4-dinitrophenyl (DNP)-protein conjugates. Spleen cell suspensions were prepared and incubated in the presence of various DNP protein conjugates, the proteins alone, and DNP-lysine. The antigen dependent stimulation of DNA synthesis was used as a measure of the antigenic ‘activity’ of the DNP preparations. It was found that the cells were strongly stimulated by the DNP-protein conjugates used for immunization, and weakly stimulated by the protein alone. Highly substituted DNP protein conjugates were markedly more effective than lightly substituted conjugates. DNP-conjugates with proteins other than the one used during immunization were inactive. DNP-lysine alone was inactive but inhibited stimulation by the DNP protein conjugate used for immunization. The significance of these findings is discussed. [ABSTRACT FROM AUTHOR]