ABSTRACT
Systemic lupus erythematosus [SLE] predominantly affects women during their reproductive years. Its pathogenesis has been postulated to involve T cells hyperactivity that can be induced by over-expression of signaling molecules such as CD40 ligand [CD40L] on T cells. This is supposed to lead to B cells proliferation, differentiation and autoantibodies production. To investigate the immunological effects of estrogen on CD40L expression on T cells in vivo as well as its relation to disease activity in SLE female patients. Thirty SLE female patients were included in this study. They are subdivided into two groups: Group Ia: 15 SLE patients during their reproductive years and Group IIa: 15 post menopausal SLE patients. The clinical activity of the disease was assessed with SLE disease activity index [SLEDAI]. The results were compared to two control groups: Group Ib: 10 normal females during their reproductive years and Group IIb: 10 normal postmenopausal women. Routine investigations were performed. Serum estradiol was assessed with electrochemiluminescence immuno-assay. Whole blood was used to determine CD40L expression on T lymphocytes with direct immunofluorescence technique. Renal biopsy was performed for SLE patients only. CD40L expression on T cells was significantly higher in group Ia than in group IIa [p<0.01]. Also it was significantly higher in group Ia than that in group Ib [p<0.01]. There was no significant difference between both groups regarding estrogen level [p>0.05]. In spite of that, SLEDAI score was significantly higher in group Ia than that in group IIa [p<0.01]. Also 24 hrs urinary protein was significantly elevated in group Ia than that in group IIa [p<0.01] while creatinine clearance and serum C3 level were significantly reduced in group Ia than that in group IIa. Of group Ia 66.7% had WHO class IV and V glomerulonephritis [GN] as compared to only 6.7% of group IIa [p<0.01]. There was a non-significant difference between groups IIa and IIb regarding CD40L expression on T cells [p>0.05]. Also, there was a significant correlation between CD40L expression on T cells, estrogen level and SLEDAI score in groups Ia and IIa patients [p<0.01]. On the other hand, there was a non-significant correlation between CD40L expression on T cells and estrogen level in groups Ib and IIb [p>0.05]. Estrogen plays an important role in the pathogenesis of SLE through increasing the expression of CD40L on T cells in SLE female patients, but not in normal females. This action is dose-dependent as we found that CD40L expression on T cells was significantly higher in SLE female patients during their reproductive years than during their postmenopausal years. Again, its level correlated well with markers of disease activity i.e. SLEDAI