CD5 antigen-positive B lymphocytes in human B cell ontogeny during fetal development and after autologous bone marrow transplantation.

We examined bone marrow and peripheral blood specimens from pediatric acute lymphoblastic leukemia (ALL) patients after autologous bone marrow transplantation (BMT) as well as fetal lymphohematopoietic tissues for the presence of CD5+ B lymphocytes. CD5+ B lymphocytes represented 23.6 +/- 0.7% of CD19+ fetal spleen B lineage lymphoid cells, 24.2 +/- 2.5% of CD19+ fetal bone marrow B lineage lymphoid cells and 18.1 +/- 1.7% of CD19+ fetal liver B lineage lymphoid cells. By comparison, in normal pediatric bone marrow samples, only 1.5 +/- 0.3% of lymphoid cells and 4.3 +/- 0.2% of CD19+ B lineage lymphoid cells expressed CD5 antigen. Similarly, very few CD5+CD19+ cells (< or = 2% of lymphoid cells) were found in day 30 and day 100 post-BMT bone marrow or peripheral blood specimens from B lineage ALL patients undergoing autologous BMT using autografts purged ex vivo with B43(anti-CD19)-PAP immunotoxin plus 4-hydroperoxycyclophosphamide (4-HC). Two bone marrow samples that were obtained and analyzed 1 year post-BMT contained only 2 to 4% CD5+CD19+ cells, accounting for 5 to 7% of the total CD19+ population. The fraction of CD5+ B lymphocytes in post-BMT bone marrow samples was not greater than the fraction of CD5+ B lymphocytes in normal healthy bone marrow.