BiP may have an immunoregulatory function mediated through IL-10 production

Aim

We have recently described BiP, a ubiquitous chaperone protein and member of the heat shock protein 70 family, as an autoantigen in rheumatoid arthritis (RA). Animal studies showed that pretreatment with BiP conferred protection from adjuvant arthritis in rats and collagen induced arthritis in mice.

Methods

Peripheral blood mononuclear cells (PBMC) were stimulated with recombinant human (rhu) BiP, rhu β-galactosidase (β-gal) and lipopolysaccharide (LPS) in the presence or absence of polymyxin B (polyB). Supernatants were collected after 24 hours and IL-10, TNF-α, IL-1β were measured by ELISA. Proliferation was measured by uptake of tritiated thymidine following stimulation of PBMC by tuberculin PPD in the presence and absence of BiP at 5 days.

Results

BiP induced production of IL-10 was significantly higher than that induced by β-gal (P = 0.008) and LPS (P = 0.033). Polymyxin B caused no inhibition of cytokine release following rhu BiP stimulation (-polyB: 4.8 ± 1.5 ng/ml vs. +polyB: 4.6 ± 1.6 ng/ml) although IL-10 secretion by rhu β-gal (-polyB: 4.3 ± 1.1 ng/ml vs. +polyB: 1.7 ± 0.4 ng/ml) and LPS (-poly B: 3.2 ± 0.8 ng/ml vs. +polyB: 1.6 ± 0.7 ng/ml) was significantly reduced. BiP stimulation induced TNF-α production at a lower concentration than IL-10 and none was detectable 96 hours post-stimulation. The proliferative response of PBMC to tuberculin PPD was significantly reduced by the presence of BiP (P = 0.0128).

Conclusions

The increased production of IL-10 induced by rhu BiP stimulation was not due to LPS contamination of the recombinant protein. BiP may have an immunoregulatory role mediated through the production of IL-10.