Antibody response to phosphorylcholine in vitro. I. Studies on the frequency of precursor cells, average clone size and cellular cooperation

Publisher Website
Google Scholar
Abstract
The anti-phosphorylcholine (PC) antibodies synthesized by BALB/c spleen cells in microcultures upon immunization with heat-killed vaccine of Pneucocci R36A (Pn) are directed exclusively to the PC epitope. These antibod are of very restricted avidity and 88 % of the responding clones express the idiotype characteristic of the TEPC-15 PC-binding myeloma. This idiotypi restriction appears to be due to the absence of clones capable of expressins other idiotypes, rather than to “clonal dominance”. The estimated frequency of precursor cells for the PC epitope is 1 × 10− to 2.5 × 10−5. These precursors give rise to clones with an average size of 9 plaque-forming cells. When the logarithm of the numberof negative wells was plottedagainst the number of spleen cells/well, the fraction of nonresing cultures decreased exponentially as the number of spleen cells was increased. This indicated that only one cell type was limiting in our assay, presumable B cell. Furthermore, treatment of spleen cells with AKR anti-Θ serum completelyabolished the response to sheep red cells without affecting the response to. It is concluded that PC is a T cell-independent antigen. Of interest was the finding that PC requires adherent (A) cells and this is a particular character of PC, since most T cell-independent antigens have been found not torequire A cells. Reasons for the possible homogeneity of the response to PC are a discussed.