The frequency of phosphorylcholine specific B cells in conventional and germfree balb/C Balb/c

The frequency of B cells specific for phosphorylcholine (PC) in spleens of nonimmune conventionally reared and germfree adult Balb/c mice was determined by an in vitro splenic focus technique. Analysis of spleen cells from 11 conventionally reared donors revealed an average of 19.1 PC specific clonal precursor cells/10⁶ donor B cells when calculated utilizing a cloning efficiency previously determined for the in vitro splenic focus technique of 4%. This number is one tenth the frequency determined for 2,4 dinitrophenyl and 2,4,6 trinitrophenyl specific B cells; however, idiotypic and isoelectric analysis reveal that the majority of B cells specific for PC yield monoclonal antibodies which share the TEPC 15 idiotype and contain a homogenous IgM peak with a pK of 4.60. Thus, this single clone appears on the average to be represented by more than 10³ B cells in conventionally reared nonimmune adults. A similar frequency for precursor cells of this clonotype was found in an analysis of 7 germfree adult mice so that the high frequency of B cells of this clonotype appears to be independent of previous antigenic stimulation. Among the 11 conventionally reared donors analyzed, frequencies varied from 1.6 to 52/10⁶ B cells, an extreme degree of variation when compared to the almost invariant frequencies observed for 2,4 dinitrophenyl, 2,4,6 trinitrophenyl, and fluoroscein. This variation is interpreted as a reflection of the life cycle of a single clone with a possible role for antigen implied by smaller variations observed in germfree mice.