The production of immunoregulatory factors by a human macrophage-like cell line. III. The relationship between the lymphoid-specific inhibitor of DNA synthesis and gamma-interferon

Normal mitogen-induced suppression of the interleukin-6 (IL-6) response and its deficiency in systemic lupus erythematosus

A low-frequency suppressor-cell population in normal peripheral blood inhibits the B-cell CESS response to IL-6, following pokeweed mitogen stimulation. The suppression of IL-6 responsiveness is (i) radiation sensitive, (ii) directed against CESS targets and not mediated by inhibition of IL-6 production, and (iii) associated with nonspecific cytotoxic activity against CESS targets. The generation of these cytolytic cells is also radiation sensitive. A correlation was found between PWM-induced cytotoxicity against CESS and the suppression of IL-6-dependent IgG production. But cytotoxicity toward CESS targets is not responsible for this suppression because (i) IL-2 induces equivalent or greater nonspecific cytotoxicity against CESS in the total absence of suppression of CESS-derived IgG production and (ii) suppression is also induced by mitogen-activated PBL separated from CESS targets by a cell-impermeable membrane. This suppression was not mediated by TNF alpha/beta or IFN-gamma. In systemic lupus erythematosus, suppression of IL-6-dependent IgG production is impaired in patients with active disease (29.2 +/- 13.7%) compared to patients with inactive disease (70 +/- 19.5%) or normal controls (82.8 +/- 9.2%). There is also a defect in mitogen-induced nonspecific cytotoxicity in active SLE (specific lysis 15.1 +/- 3.5%, compared to 34 +/- 4% in normals). Pokeweed mitogen-activated PBL can therefore normally induce suppression of B-cell IL-6 responses and this response is deficient in lupus.

The characterization of a human B cell line utilizable for the assay of B cell growth factors

An EBV-transformed B cell line JR-2(82) is described which proliferates in response to human B cell growth factor (BCGF) preparations. Although spontaneous replication occurs at high cell densities, at cell densities of 10(3) cells or less, cell death occurs in the absence of BCGF. This response is not dependent upon the presence of low concentrations of supplemental serum in the culture medium. There is no proliferative response to various preparations of interleukin (IL)-1, IL-2 or gamma-interferon (gamma-IFN) up to 1000 U/ml either alone or in combination and specific antisera to IL-2 and gamma-IFN do not interfere with the proliferative response. At 5000 U/ml of gamma-IFN or greater, a partial proliferation of the line is seen to 30% of maximal. The JR-2(82) line and its clones appear to proliferate preferentially in response to low molecular weight (LMW) BCGF, compared to the response seen to high molecular weight (HMW) BCGF from Namalwa cell line supernatants. The line does not produce Ig spontaneously but on incubation with B cell differentiation factor (BCDF) containing supernatants differentiates to an IgG-producing cell line. JR-2(82) or its derivatives may therefore provide a simple reproducible assay for BCGF in the presence of other lymphokines and may be used to study further the interactions of lymphokines in the regulation of the proliferation of EBV-transformed cells.

Interaction of a lymphokine with normal human macrophages results in release of a suppressor factor for mitogen-induced immunoglobulin synthesis

Normal human macrophage/monocyte cultures exposed to a suppressor factor produced by concanavalin A-activated T cells (T-SF), respond by releasing after 72 h a macrophage-derived suppressor factor (M phi-SF). The M phi-SF inhibits pokeweed mitogen-induced Ig synthesis but not T- or B-cell proliferation. Cycloheximide treatment of the macrophages does not interfere with generation of the M phi-SF, suggesting that de novo synthesis is not required. The factor is not preformed, for virgin macrophages do not contain M phi-SF, but it appears in macrophage cell lysates after exposure to T-SF. The production of the M phi-SF is inhibited by the presence of 2-mercaptoethanol. Both T-SF and M phi-SF are L-rhamnose inhibitable, and the M phi-SF appears to be released as a high molecular weight complex which is dissociable into a low molecular weight form of a size similar to the T-SF, i.e. approximately 20,000. The T-SF induced M phi-SF has some similarities with soluble immune response suppressor (SIRS) but differs from this factor in its lack of effect upon lymphocyte proliferation failure to induce conversion of T-SF to M phi-SF by treatment with H2O2.