Cryoglobulins induce temperature-dependent TNF-α production via Fcγ-receptor II

Introduction

Cryoglobulins (CG) are antibodies that reversibly agglutinate and form immune complexes (IC) when plasma or serum is cooled below normal body temperature. Precipitation of CG is also known to depend on pH and ionic strength. We have previously shown that IC from SLE-patients can induce cytokine production from peripheral blood mononuclear cells (PBMC). We have investigated if, and under which circumstances, CG can also induce cytokine production.

Methods

CG from two patients were purified under sterile conditions. One patient was a 71 years old male with an IgG multiple myeloma and an IgG CG. The other patient was a 58 years old female with Waldentröm's macroglobulinemia and an IgM CG. The purified CG were added to PBMC cultures. Cytokine production in the supernatants was measured with ELISA. Fcγ-receptors were blocked with specific antibodies against FcγRII and FcγRIII. In separate experiments temperature, ionic strength and pH were varied.

Results

CG, especially IgG CG, induce production of TNF-α and IL-1β . This cytokine production was partly blocked by anti-FcγRII antibodies but not by antibodies to FcγRIII. When CG were added to PBMC at 4°C and 37°C respectively, more TNF-α production was seen in cultures with CG added at 4°C. The IgG and IgM CG showed maximal precipitation at different ionic strength, with parallel differences in TNF-α production in cell cultures with varying ionic strength. Parallel studies on the effects of pH on CG precipitation and cytokine production are underway.

Conclusions

CG-induced cytokine production varies with temperature, ionic strength and pH, and is at least partly mediated via FcγRII. CG-induced production of proinflammatory cytokines might be of importance in CG-associated vasculitis/nephritis. Modulation of CG precipitation and ensuing cytokine production may gain therapeutic importance.