To analyze the immunoglobulin repertoire of human IgM ϩ
B cells and the CD5ϩ and CD5 Ϫ subsets, individual CD19 ϩ / IgM ϩ /CD5 ϩ or CD5 Ϫ B cells were sorted and non-productive as well as productive V H gene rearrangements were amplified from genomic DNA and sequenced. In both subsets, the V H 3 family was overrepresented largely as a result of preferential usage of a small number of specific individual family members. In the CD5 ϩ B cell subset, all other V H families were found at a frequency expected from random usage, whereas in the CD5 Ϫ population, V H 4 appeared to be overrepresented in the nonproductive repertoire, and also negatively selected since it was found significantly less often in the productive compared to the nonproductive repertoire; the V H 1 family was significantly diminished in the productive rearrangements of CD5 Ϫ B cells. 3-23/DP-47 was the most frequently used V H gene segment and was found significantly more often than expected from random usage in productive rearrangements of both CD5