Genetic influence on the levels of circulating CD5 B lymphocytes.

By using sensitive two- and three-color immunofluorescence analyses, we readily detect CD5B cells (Leu 1 B cells) in the peripheral blood of normal adults. These circulating CD5 B lymphocytes coexpress B cell differentiation antigens CD20, CD21, CD19, sIgM and sIgD, and HLA-DR. Unlike CD5-negative B cells from most adults, however, these cells co-express CD11, a finding also noted for malignant CD5 B cells from several patients with CLL. Between normal volunteers, there exists heterogeneity in the proportion of PBL that co-express CD5 and B cell surface antigens, such cells representing between 0 and 6% of peripheral lymphocytes. Despite such heterogeneity between unrelated individuals, analyses of repeated blood samples from the same person reveal that the proportions of CD5 B lymphocytes are constant over time. Examination of blood samples from related family members, monozygotic twins, and triplets indicate that the relative proportion of circulating CD5 B cells may be genetically regulated. This is apparent even for monozygotic twins discordant for rheumatoid arthritis. Four sets of such twins are examined, each set having one individual with clinically active, seropositive rheumatoid arthritis and another without detectable rheumatoid factor or clinical pathology. Despite such noted differences, twins from each set share identical proportions of circulating CD5 B cells. In summary, our studies indicate that the level of CD5 B lymphocytes is a rather stable phenotypic trait that is under genetic control.