Subpopulations of T alpha cells in patients with IgA nephropathy: correlation between T alpha 4 cells and in vitro IgA production.

T cells play important roles in the regulation of the immune system and are divided into subpopulations by various kinds of markers on the membrane surface. T cells with Fc-receptors for IgA are termed T alpha cells, and the properties of this cell population have been revealed in recent years. T alpha cells are increased in patients with IgA nephropathy and possess IgA specific helper activity. T alpha cells consist of two subpopulations, T alpha cells with OKT4 antigen (T alpha 4 cells) and with OKT8 antigen (T alpha 8 cells). To investigate the immunological aberrations in patients with IgA nephropathy, we detected immunoglobulin produced by peripheral blood lymphocytes and enumerated the numbers of T alpha cells (including both T alpha 4 and T alpha 8 cells). The numbers of T alpha 4 cells (but not T alpha 8 cells) and in vitro IgA production were increased in patients with IgA nephropathy (IgA nephropathy, mean 1.9%. Control, mean 0.8%. P = 0.0075). In addition, the numbers of T alpha 4 cells and the amount of IgA in the supernatant of lymphocyte cultures were positively correlated in these patients (P = 0.025. r = 0.3836). From the results in the present study, it was suggested that T alpha 4 cells might be related to immunological aberrations, such as an increase in IgA seen in patients with IgA nephropathy.