Figure 1.

Soluble antigen differentially affects primary and secondary immune responses. A, Immunization schedule. The initial immunization was with 100 μg of Ars₁₅-KLH i.p. in IFA (n = 4–5 mice/group). The primary injection series on days 7–20 was in PBS. B, Differential effects of primary injection series on overall affinity of Ab in the late primary and secondary immune responses. Dilution points at 50% of maximum binding were determined and used to calculate the ratios shown. High affinity Ab selectively bind Ars₅-BSA Ab, while both high and low affinity Ab bind Ars₁₅-BSA. C, Relative affinities among higher affinity Ab in late primary and secondary immune response sera. Trays were coated with Ars₅-BSA. Sera were used a dilution giving 90% of maximal binding on Ars₅-BSA. Ordinate indicates Ars-Tyr concentrations at which binding to Ars₅-BSA was inhibited by 50% (I₅₀). Each point is average of Log₁₀ I₅₀ for 4–5 mice. Lower concentration indicates higher affinity Ab. Standard errors indicated. D, Anti-Ars titers defined as dilution at 50% of maximal binding on Ars-BSA for day 41 sera. E, Fold increase in anti-Ars titers between days 230 and 244 as assessed on Ars₅-BSA.