The frequency of phosphorylcholine-specific B cells in conventional and germfree BALB/C mice.

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/10-6 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-trintrophenyl-specific B cells; however, both 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 homogeneous IgM peak with a pK of 4.60. Thus this single clone appears on the average to be represented by more than 10-3 B cells in conventionally reared nonimmune adults. A similar frequency for precursor cells of this clonotype was found in an analysis of seven germfree adult mice so that the high frequency of B cells of this colontype appears to be independent of previous antigenic stimulation. Among the 11 conventionally reared donors analyzed, frequencies varied from 1.6 to 52/10-6 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 grem free mice.