B-cell proliferative and differentiative responses after autologous peripheral blood stem cell or bone marrow transplantation

In this study the authors have evaluated B-cell function after autologous peripheral-blood stem cell transplantation (ABSCT) and autologous bone marrow (ABMT) transplantation. The B-enriched fractions of peripheral blood from ten normal subjects and 22 autografted patients (11 patients after ABMT, eight patients after ABSCT, and three patients after ABSCT followed by ABMT) were investigated. Time postgrafting ranged from 1 to 34 months. Proliferative responses to anti-mu antibody, Staphylococcus aureus Cowan 1 (SAC), and low molecular weight (mol wt) 12-Kd B-cell growth factor (BCGF) were measured. Differentiative responses to the same factors were assessed by quantifying in vitro immunoglobulin (IgG/IgM) production. The authors found no difference in B-cell function between the ABMT and the ABSCT patient groups. Compared to the B cells of normal subjects, only five out of 22 autografted patients showed a normal proliferative response to all agents used, while nine out of 22 did not respond to any signals. Eight out of 22 patients displayed various defects of B- cell response. However, in vitro IgG/IgM secretion of predominantly IgG subclass was normal in 19 out of 22 patients. This in vitro ability to produce Ig was reflected by the patients' normal serum IgG/IgM levels, whereas serum IgA levels were low. The authors speculate that there may be 2 B-cell populations: the normal in vitro Ig production and in vivo serum IgG may come from the stimulation of a small number of re-infused pre-committed memory B cells while, in parallel, immature B cells develop from autografted hematopoietic progenitor cells.