Abnormality and significance of interleukin-9 and CD4(+)interleukin-9(+) T-cells in peripheral blood of patients with systemic lupus erythematosus

Abstract

To examine the protein and mRNA levels of interleukin-9(IL-9) and the frequencies of CD4(+)IL-9(+)T-cells in peripheral blood of patients with systemic lupus erythematosus (SLE) and explore the roles of double positive T cells and IL-9 in the pathogenesis of SLE and the effects of glucocorticoid. Twenty-eight hospitalized SLE patients were recruited and 12 healthy volunteers selected as normal controls. The mRNA levels of IL-9 in peripheral blood were measured by real time-polymerase chain reaction (RT-PCR), plasma protein of IL-9 by enzyme-linked immunosorbent assay (ELISA) and frequencies of CD4(+)IL-9(+)T-cells by flow cytometry. And the differences between two groups and the effects of glucocorticoid were analyzed. (1) The mRNA levels of IL-9 were significantly elevated in SLE patients as compared with normal controls (P < 0.01). The serum levels of IL-9 were significantly higher in active and inactive SLE patients than those in healthy individuals (68 ± 11 vs 26 ± 6 ng/L, P < 0.01; 56 ± 14 vs 26 ± 6 ng/L, P < 0.05). The percentages of CD4(+)IL-9(+)T-cells increased in active SLE patients (1.96% ± 0.31%) versus inactive SLE patients (0.89% ± 0.13%, P < 0.01) and healthy controls (0.28% ± 0.05%, P < 0.001). And it was higher in inactive SLE patients than that in controls (P < 0.05). (2) The serum levels of IL-9 and the frequencies of CD4(+)IL-9(+)T-cells were positively correlated with SLE disease activity index (SLEDAI). (3) The frequencies of CD4(+)IL-9(+)T-cells and the serum levels of IL-9 in 8 untreated active SLE patients decreased at weeks 1, 2 and 3 after the therapy of methylprednisolone (0.8 mg×kg(-1)×d(-1)) versus those at pre-treatment. The abnormalities of IL-9 and CD4(+)IL-9(+)T-cells may play an important role in the pathogenesis of SLE. And the frequencies of CD4(+)IL-9(+)T-cells and the levels of IL-9 are evaluative parameters of SLE activity and severity.