Increased IL‐10 production by stimulated whole blood cultures in primary IgA nephropathy
Most patients with primary IgA nephropathy (IgAN) have a significantly higher memory repertoire of IgA1‐producing B lymphocytes in their bone marrow together with high plasma levels of IgA1. The connection between the mucosal immune system and the bone marrow compartment is probably based on traffic of either antigen‐presenting cells (APC) or antigen‐specific lymphocytes. Cytokines play an important role in the proliferation and differentiation of lymphoid cells. In order to mimic the in vivo situation as much as possible, we assessed cytokine production profiles ex vivo in 23 IgAN patients and matched controls, using lipopolysaccharide (LPS)‐ or phytohaemagglutinin (PHA)‐stimulated whole blood (WB) cultures. Interferon‐gamma (IFN‐γ), IL‐2, IL‐6, IL‐10 and tumour necrosis factor‐alpha (TNF‐α) production in culture supernatants were determined by cytokine‐specific ELISAs. Compared with controls, PHA‐stimulated cultures resulted in significantly higher IL‐10 (P < 0.001), IL‐2 (P < 0.005) and IFN‐γ (P < 0.001) levels in IgAN patients, but no significant differences in TNF‐α or IL‐6 levels were found. In LPS‐stimulated cultures, the only significant difference (P < 0.001) between the two groups was the increased IL‐10 production in IgAN patients. The enhanced cytokine production in stimulated WB cultures suggests altered monocyte‐related T cell responses in patients with IgAN. Increased IL‐10 production may eventually result in an increased number of IgA‐producing B lymphocytes in the bone marrow. In addition, high levels of endogenous IL‐10 may down‐regulate the effector functions of monocytes, or possibly APC in general, and consequently the IgA response at the mucosal level.