INFLUENCE OF ANTIGEN ON A MODEL FOR ANALYSIS OF MULTIPLE COORDINATE EVENTS ASSOCIATED WITH THE PRIMARY IMMUNE-RESPONSE

The influence of sheep red blood cells (SRBC), a T-dependent antigen, was analyzed in an experimental model of multiple coordinate functions of the immune response. The influence of antigen dose on the kinetics with which splenic B and T antigen-binding lymphocytes (ABL) and plaque-forming cells (PFC) developed, and the relative ratio of each of these cellular subsets were analyzed during the primary immune response to SRBC. As a function of increased antigen dose: 1) the total number of ABL increased, with relative increases on day 3 < day 5 > day 7; 2) the number of direct PFC increased, with relative antigen-dependent increases on day 3 > day 5 > day7; and 3) mean PFC lytic plaque volume progressively decreased. At low antigen doses, T ABL preferentially increased relative to B ABL, whereas at high antigen doses the reverse was observed. Thus, the increased capacity for a secondary response after a primary immunization at low antigen doses could be a consequence of the greater numbers of T ABL induced by small quantities of antigen. Both the rate of proliferation of ABL and their differentiation to PFC were influened positively by increasing doses of antigen; however, the ratio of PFC to ABL was higher at low antigen doses, suggesting that the relative rate of differentiation of ABL to PFC was greater than the rate of proliferation of ABL under conditions of limited antigen dose. Mean lytic plaque volume decreased slightly with time and markedly with increasing antigen dose. This could reflect shifts in binding affinity, mean antibody secreted per antibody-forming cell, or both. Whereas each of these parameters have been separately reported, the coordinate use of each provides a more critical analysis of each of the antigen-specific cell populations that participate in a response and their modification by immunoregulatory factors or events. © 1979.