Expression of Th1/Th2 cytokine mRNA in peritoneal exudative polymorphonuclear neutrophils and their effects on mononuclear cell Th1/Th2 cytokine production in MRL‐lpr/lpr mice

Abstract

Peritoneal exudative polymorphonuclear neutrophils (PEC‐PMN) and mononuclear cells (PEC‐MNC) were obtained from normal BALB/c and from autoimmune MRL‐lpr/lpr mice (lpr) with different disease severities. The spontaneous and mitogen‐stimulated expression of T‐helper lymphocyte type‐1 (Th₁) [represented by interferon‐γ (IFN‐γ) and interleukin (IL‐2)] and T‐helper lymphocyte type‐2 (Th₂) (represented by IL‐4 and IL‐10) cytokine mRNA in these cells was detected by reverse transcription‐polymerase chain reaction (RT–PCR). The production of these cytokines was measured by enzyme‐linked immunosorbent assay (ELISA). We found that the spontaneous expression of Th₁/Th₂ cytokine mRNA in PEC‐PMN from autoimmune mice was progressively increased in parallel with disease severity but was not changed by lipopolysaccharide (LPS) stimulation. By contrast, spontaneous expression of Th₁/Th₂ cytokine mRNA in PEC‐MNC from these mice was progressively decreased in parallel with disease severity but retained the responsiveness to phytohaemagglutinin (PHA) stimulation. To determine the effect of PEC‐PMN on Th₁/Th₂ cytokine production by PEC‐MNC, autologous PEC‐PMN and PEC‐MNC were co‐cultured at MNC:PMN ratios of 5:0, 4:1, 3:2, 2:3, 1:4 and 0:5 with PHA stimulation for 24 hr. The production of cytokines at each ratio was compared with the expected value, by calculation. We found that PEC‐PMN from autoimmune mice progressively suppressed the production of IL‐4, IL‐10 and IFN‐γ whereas the production of IL‐2 was enhanced by autologous MNC in parallel with disease severity. These results suggest that a reciprocal relationship exists in the expression of Th₁/Th₂ cytokine mRNA between PEC‐PMN and PEC‐MNC in lpr mice in parallel with disease severity. Autoimmune PEC‐PMN can exert significant modulatory effects on Th₁/Th₂ cytokine production by autologous MNC in stimulation.