Two distinct subsets of patients with systemic lupus erythematosus

Abstract

This study was undertaken to examine the levels and function of peripheral blood immunoregulatory T cell subpopulations in systemic lupus erythematosus (SLE). T cell subpopulations can be distinguished by the T cell differentiation antigens CD4 (recognized by the monoclonal antibodies OKT4 or Leu3) and CD8 (recognized by the monoclonal antibodies OKT8 or Leu2). All SLE patients tested had normal percentages of CD8 cells in their peripheral blood. The SLE patients, however, fell into two groups based on their CD4 cell numbers. Fifty-five percent of the SLE patients had normal levels of CD4 cells (Group A) and therefore normal CD4/CD8 cell ratios, whereas 45% of the SLE patient population had markedly depressed CD4 cell levels (Group B) and significantly low CD4/CD8 cell ratios. T cells from normal donors and SLE patients were further examined for their ability to stimulate allogeneic normal B/Mφ cells cells to secrete IgM in the presence of pokeweed mitogen (PWM). Utilizing this assay system two forms of immunosuppression were observed: (1) that mediated by high concentrations of purified CD4 cells and (2) that mediated by CD8 cells. High concentrations of purified CD4 cells, added to a constant number of allogeneic normal B/Mφ cells, suppressed PWM-stimulated IgM synthesis. Group B SLE patients, with significantly low CD4 cell numbers, had defective CD4 cell-mediated suppression which was concentration dependent. This result was confirmed in a study using identical twins discordant for SLE. In this case CD4 cells from the SLE twin did not induce immunosuppression at a high concentration of CD4 cells whereas similar concentrations of CD4 cells from the normal twin resulted in suppression. SLE patients (Group A) with normal levels of CD4 cells had normally immunosuppressive CD4 cells. Suppression mediated by CD8 cells was demonstrated by the fact that removal of CD8 cells resulted in enhanced IgM synthesis induced by the remaining CD4 cells. Although all the SLE patients in this study had normal peripheral blood levels of CD8 cells, SLE Group A patients had defective CD8 cell suppression whereas CD8 function appeared to be normal in Group B patients. These results suggest that in SLE patients with depressed CD4 cell numbers (Group B) there is a corresponding defect in CD4 cell function. We demonstrate that in SLE Group B patients, defective suppression is due to a subset of T cells that bear the CD4 antigen. The SLE patient population (Group A) with normal CD4/CD8 ratios and normally functioning CD4 cells, however, appear to have normal CD4 cell-mediated suppression but defective CD8 suppressor cell function.