Requirement for continuous antigenic stimulation in the development and differentiation of antibody-forming cells. The effect of passive antibody on the primary and secondary response.

The essential role of continuous antigenic stimulation in the development and differentiation of antibody-forming cells as defined in the X-Y-Z immune cell maturation scheme was examined in these studies. Mice were primed with sheep erythrocytes (SRBC) in an attempt to induce maximum immune progenitor cell conversion (X --> Y). Subsequently antigen was depleted at 1 or 4 days after priming with isologous specific antibody in order to interrupt further immune cell differentiation (Y --> Z). It was reasoned that this condition would result in depression of the functional antibody-producing cell compartment as measured in the intact mice and subsequently in enhancement of the sensitized (Y cell) compartment as measured in the spleen cell transfer system. These data were also correlated with systematic studies of the hyperplasia of the spleen germinal centers. The effect of passive antibody on the primary response to SRBC was a marked decrease indirect and indirect hemolysin-producing cells (DPFC and IPFC). However, there was a lack of correlation in the degree of antibody-mediated 19S and 7S immune cell suppression during the primary response, the DPFC being much less depressed than the IPFC. As measured in the transfer system there was an enhanced 19S sensitized cell compartment and a depressed 7S sensitized cell compartment in 1 day passively immunized mice. This was true whether or not transfers were performed 1, 2, or 4 wk after priming. Similarly, there was an enhanced 19S-sensitized cell compartment with little or no effect on the 7S-sensitized. cell compartment in 4 day passively immunized mice. These data suggest that progeny of the antigen-stimulated progenitor cells (X cell), as a consequence of lack of further antigenic stimulation, were forced into maturation arrest. These studies further demonstrate that isologous passive antibody suppresses germinal center growth regardless of whether the antibody is infused 1, 2, or 4 days after priming. In terms of formation of sensitized cells, the marked depression of 7S sensitized cell compartment after passive immunization at 24 hr in contrast to the enhancement of the 19S sensitized cell compartment corresponds to the suppressed growth of germinal centers during the primary response. Thus, if the germinal center is, as suggested, the site of proliferative expansion of immunocompetent cells, these data indicate that the germinal center growth is related to the 7S antibody response and in the formation of "7S memory."