CD5 positive immunoregulatory B cell subsets.

B-chronic lymphocytic leukemia (B-CLL) is a heterogeneous disease often expressed as a clonal expansion of CD5+ B cells. We report the characterization of CD5+ B cells from two unique B-CLL patients. Cells from patient 1 coexpressed CD5 (leu-1), CD19 (Leu-12), CD20 (B1), and HLA-DR; they were CD10 (J5), CD21 (B2), CD22 (Leu-14), CD25 (IL2-R1), PCA-1, surface, and cytoplasmic Ig negative. They suppressed normal peripheral blood lymphocyte (PBL) pokeweed mitogen (PWM) -stimulated immunoglobulin (Ig) synthesis greater than 80%. Cells from patient 2 were CD5 (Leu-1), CD19 (Leu-12), CD20 (B1), CD21 (B2), CD22 (Leu-14), HLA-DR, IgM, and kappa positive. They were negative for CD10 (J5), CD25 (IL2-R1), and PCA-1. These cells did not suppress normal PBL PWM-stimulated Ig synthesis but produced a monoclonal IgM kappa protein with rheumatoid factor-like activity. These observations suggest that there are different CD5+ B cell subsets, one immunosuppressive and the other autoreactive.