Soluble interleukin-2 receptor levels and immune activation in patients with schistosomiasis and carcinoma of the urinary bladder.

Soluble interleukin-2 receptor (sIL-2R) level in serum is a marker of immune regulation and lymphocyte activation. Highly elevated levels of sIL-2R in serum were observed in patients of schistosomiasis with carcinoma of the bladder (SCB) and carcinoma of the bladder without schistosomiasis (CB) compared with patients with carcinoma of the prostate with or without schistosomiasis and normal healthy controls. Patients with SCB, who had an elevated percentage of cells expressing CD38+ activation antigen and CD71+ transferrin receptors in circulation, also had elevated levels of sIL-2R in serum. There were few interleukin-2 receptor (CD25+) positive cells in circulation in some patients with SCB. Despite this, the sIL-2R levels were extremely elevated. Our data suggest that in SCB, CD38+ and CD71+ cells may be the source of secretion of sIL-2R in serum. This relationship was confirmed by phenotypic characterizations of mononuclear cells and sIL-2R levels in individual patients. Measurements of sIL-2R levels in serum may provide a sensitive method of immune activation in patients with SCB.