B cell tolerance induced by polymeric antigens. V. Different avidities of primed and virgin precursor cells for paucivalent antigen.

We have compared the avidity of virgin and primed hapten-specific precursor cells for DNP-lys-S3 (dinitrophenylated type 3 pneumococcal polysaccharide) by measuring its capacity to prevent them from binding highly radioactive DNP-hemocyanin, and thereby protect them from committing hapten-specific "suicide". Moderately substituted conjugates (e.g. DNP-lys2.7S3) protected virgin and memory B cells impartially. In contrast, DNP-lys0.6S3 protected memory cells efficiently, but protected virgin cells only at considerably higher concentrations. These results are consistent with previous evidence - from this and other systems - that there is a higher density of receptors on primed than on unprimed B cells - the significance of which is discussed.