Determinants of soluble CD23 antigen levels in hemodialysis patients: effect of 1.25 dihydroxyvitamin D-3 and recombinant human erythropoietin treatment

Background: The immunodeficiency of end-stage renal disease (ESRD) paradoxi cally coexists with T cell and monocyte activation. In spite of well known defective antibody responses in ESRD, the functional status of B cells in t he immune system dysregulation of uremia is still controversial. Soluble CD 23 (sCD23) antigen is a recently identified B cell activation marker and is also involved in T cell activation process. Effects of parathyroid hormone (PTH), red blood cells and ferritin on T and B cell functions have been sh own both in vivo and in vitro. Patients and methods: In this study, serum l evels of sCD23 in hemodialysis patients were determined to evaluate the fun ctional status of B cells and possible linkages between this cytokine and P TH levels, ferritin levels, red blood cell counts were investigated. Result s: Serum sCD23 levels were significantly elevated in hemodialysis patients relative to healthy controls (12.5 +/- 8.4 mu/l vs 2.4 +/- 1.1 mu/l, p < 0. 001). Serum sCD23 levels were negatively correlated with red blood cell cou nt (r = -0.61, p = 0.009) and serum PTH levels (r = -0.62, p = 0.008, while positively correlated with serum ferritin levels (r = 0.63, p = 0.007) in hemodialysis patients. We also investigated the immunumodulator effects of 1.25 dihydroxyvitamin D-3 (1.25OHD(3)) and recombinant human erythropoietin (rHu-Epo) treatment in hemodialysis patients. 1.25OHD(3) treatment for eig ht weeks did not change serum sCD23 levels in hemodialysis patients (n = 8) . On the other side, rHu-Epo administration for 16 weeks led to a decrease in serum sCD23 levels (17.7 +/- 8.6 mu g/l vs. 9.8 +/- 3.5 mu g/l, p = 0.00 7) in these patients (n = 9). Conclusion: These results suggests that simil iar to T cells, B cells are activated in uremia and the degree of this acti vation is correlated with red blood cell count, serum parathyroid hormone l evels and iron status of the hemodialysis patients. Moreover, B cell activa tion could be altered by recombinant human erythropoietin therapy in hemodi alysis patients.