Characterization of B cells in severe combined immunodeficiency disease

The circulating lymphoid cells of eight consecutive untreated infants with severe combined immunodeficiency disease (SCID) with B cells were analyzed for surface marker expression and function. The B cells of these children expressed sIg, HLA-DR, CD19 (B4), CD20 (B1), CD21 (B2), Leu-8, and lacked expression of CD10 (CALLA), as do normal peripheral blood B lymphocytes. SCID B cells also expressed antigens that are normally absent or present on only a minor subset of circulating adult B lymphocytes, including CD1c (M241), CD38 (OKT10), CD23 (PL13), with or without concomitant CD5 (Leu-1) expression. The B cells of these children were capable of proliferating in vitro when stimulated with Staphylococcus aureus Cowan I. However, in the presence of pokeweed mitogen, S. aureus Cowan I, and normal T cells, the sIg+ cells of these children produced only IgM. Studies performed on normal B cells obtained from cord blood, young children, and adults reveal that whereas cord blood B cells are predominantly CD1c, CD38, and CD23 positive, B-cell expression of these antigens decreases with age. Cord blood B cells, similar to SCID B cells, produce only IgM when stimulated in vitro with pokeweed mitogen and S. aureus Cowan I. Based on these observations, we hypothesize that SCID B cells represent a population of B cells present during normal B-cell ontogeny which becomes a minor subset when an individual develops full immunologic competence.