Antigen‐specific mouse lymphocyte stimulation by DNP‐conjugated T‐independent antigens studied by photobleaching recovery

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Abstract
Fluorescence photobleaching recovery techniques have allowed us to measure the lateral mobility of T‐independent antigens bound to antigen‐specific mouse B cells. The in vitro immunogenicity or tolerogenicity of antigens we have examined, DNP‐polymerized flagellin (DNP‐POL), and DNP‐linear dextran (DNP‐DEX), depend upon the antigen dose and epitope density. These factors also determine the mobility of antigen bound to B cell surfaces. For DNP‐POL bound to DNP‐specific cells, the observed diffusion constants D decrease monotonically with increasing antigen dose and epitope density. Values of D range from 10.4 × 10−11 cm2 sec−1 for DNP0.4‐POL at 0.15 μg/ml to 0.8 × 10−11cm2 sec−1for DNP3.5‐POL at 30 μg/ml. For receptor‐bound DNP‐DEX, D depends strongly on antigen epitope density but not observably on antigen concentration. For epitope densities of 1.2 or less, D is close to the value of 21 × 10−11cm2sec−1 observed for single slg receptors. By an epitope density of 4.8, D has fallen to 2.1 × 10−11cm2sec−1. Peak immunogenicities for DNP‐POL and DNP‐DEX arc observed when antigen‐ receptor aggregates have mobilities 14‐fold and 3‐fold lower, respectively, than a single slg molecule.