| Abstract: | ![]()
A number of human B lymphoblast cell lines were tested to find a suitable model for induction of immunoglobulin-secreting cells (ISC) by T cell replacing factor (TRF). Partially purified TRF was size fractionated from the conditioned medium of irradiated (1000 rds) human spleen cells stimulated with pokeweed mitogen. IgM line SKW 6 showed high levels of TRF-stimulated immunoglobulin secretion and was chosen for cloning experiments. Clone 11 had a very low level of ISC with or without TRF (less than 0.1% ISC). Clone 4 had low background numbers of ISC (0.2%) and showed the highest degree of stimulation by TRF (to 6% IFC). High secreting clone 8-2 (6%) was not stimulated significantly by TRF. These clones had the same HLA-DR antigens, and their levels of ISC and sensitivity to TRF were relatively stable over three months of observation. The TRF preparation also had strong helper activity for normal peripheral blood B cell differentiation. TRF activity for both normal B cells and clone 4 cell line was absorbed by all 3 clones, but not by a pre-B line. This suggests that the effector molecules for normal B cell and cell line differentiation were the same. The three typical clones corresponding to nonresponding, responding, and high rate-secreting B cells provide basic models for analyzing B cell receptors for TRF and the biochemical effects of TRF during B cell differ entiation. |
