DNA replication as a prerequisite for the induction of primary antibody response

Studies were carried out to test whether the induction of a primary production of antibodies is determined by DNA replication. An in vitro system for the induction of antibody to dinitrophenyl (DNP) determinants following immunization with α-DNP-poly-l-lysine was employed. Cytosine arabinoside (CA), at doses which inhibited DNA synthesis, yet did not affect viability of cells, was applied at different time intervals following antigenic stimulation. Inhibition of DNA synthesis during 36–48 hr following antigenic stimulation prevented the appearance of antibody producing cells. On the other hand, CA applied during the first 36 hr or at 48 hr did not prevent antibody production. Thus, one critical cycle of DNA replication seems to determine antibody production. The lag period prior to the CA-sensitive period is antigen determined.