In vitro assays to study role of T cell-derived factors on human B lymphocytes should take into consideration inhibiting effect of large granular lymphocyte subset (CD5-,CD16+) that can contaminate B cell preparations

SV-IV, a major protein secreted from rat seminal vesicle epithelium, promotes lymphocyte cytotoxic activity against the lymphoblastoid Raji cell line in human peripheral blood mononuclear cells

The treatment of human peripheral blood mononuclear cells (PBMC) with micromolar concentrations of SV-IV, a major protein secreted from the rat seminal vesicle epithelium, promotes in this cell population a marked cytotoxic activity against the Raji lymphoblastoid cell line. This activity is apparently due to cell-to-cell contact interactions. The expression of HLA DR on Raji cells has a modulatory effect on the SV-IV-induced cytotoxic activity. The experimental evidence strongly suggests that the cytotoxic effector cells are functionally activated NK cells.

Characterization of B cell growth in systemic lupus erythematosus. Effects of recombinant 12-kDa B cell growth factor, interleukin 4 and transforming growth factor-beta

B cells from systemic lupus erythematosus (SLE) patients have been shown to be hyperactive as measured by proliferation and immunoglobulin production. We find that B cells from 6 of 13 SLE patients, in the absence of prior activation, respond two to three times better to recombinant 12-kDa B cell growth factor (BCGF) than do normal or rheumatoid arthritis B cells (p less than 0.005). B cells from normally responsive SLE patients require an anti-mu antibody activation step to generate similar proliferative signal in response to r12-kDa-BCGF. There are no clinical or serological parameters that distinguish these hyperresponsive SLE patients from the normally responsive SLE patients. The combination of r12-kDa-BCGF and interleukin 4 (IL4) gives an enhanced response with both normal and SLE B cells. Transforming growth factor type beta (TGF-beta) suppresses the response to r12-kDa-BCGF in a dose-dependent fashion using B cells from both healthy donors and SLE patients. We conclude that peripheral blood B cells are in an activated state (as detected by response to 12-kDa-BCGF) in approximately 50% of SLE patients. These B cells respond normally to regulation by IL4 and TGF-beta. A therapeutic approach aimed at reducing the B cell hyperactivity in SLE would involve suppressing the effects of 12-kDa-BCGF and IL4 while at the same time enhancing the effects of TGF-beta.

Human natural killer cells suppress the proliferation of B cells

We have investigated the suppressive effect of human natural killer (NK) cells on autologous B-cell proliferation. Removal of NK cells by anti-NK-cell monoclonal antibodies (CD16, Leu 11b; Leu 7) increased by 2-3-fold the proliferative response of purified B cells activated by anti-mu and B-cell growth factor (BCGF). The inhibitory effect of NK cells was observed using recombinant IL-2 or semi-purified BCGF-I as sources of BCGF. Moreover NK cells, highly purified by centrifugation on a Percoll discontinuous density gradient, suppressed the proliferative response of purified autologous B cells activated by anti-mu and BCGF. These results show a suppressive effect of human NK cells on B-cell proliferation in vitro.