CD4 cells from patients with autoimmune thyroid disease secrete interferon γ after stimulation by thyroid microsomal antigen; CD8 cells suppress this secretion

Abstract

The production of interferon gamma (IFN gamma) by peripheral blood mononuclear cells (PBMC) from normal persons and patients with autoimmune thyroid disease (AITD) has been studied in vitro either spontaneously or after stimulation with thyroid microsomal antigen (TMc) or liver microsomal antigen (LMc). The numbers of IFN gamma secreting cells were measured by a spot-ELISA technique. AITD PBMC spontaneously contained significantly more IFN gamma secreting cells than did normal control PBMC. Moreover, TMc antigen caused a significantly greater number of IFN gamma secreting cells in AITD PBMC than did LMc antigen, whereas there was no significant difference between the two antigens in the normal control PBMC preparations. Thus TMc antigen caused a stimulation of the number of IFN gamma secreting cells only in the AITD PBMC and not in the normal PBMC. CD4 plus B cells or CD4 cells alone (with monocytes in both instances) contained more IFN gamma secreting cells under unstimulated conditions than did CD8 cells in both groups. AITD CD4 plus B cells (or CD4 cells) contained more IFN gamma secreting cells than did normal cells, but there was no significant difference between both groups in terms of the number of CD8 IFN gamma secreting cells. Normal CD4 plus B cells (or CD4 cells) responded to TMc antigen significantly more than did total normal PBMC at 10 and 1,000 ng/ml TMc. This was not the case when patients' CD4 plus B cells (or CD4 cells) were compared with patients' total PBMC, in which there were no significant differences. This suggests that CD8 suppressor activity was inadequate in AITD and thus the deletion of CD8 cells did not result in an increase in IFN gamma secreting cells. When TMc antigen was added to AITD CD8 cells, there was a significant diminution of IFN gamma secreting cell numbers at 10 and 1,000 ng/ml TMc. Moreover, adding autologous CD8 cells to CD4 plus B cells resulted in a significant suppression of IFN gamma production at 100 and 1,000 ng/ml TMc in both groups. AITD CD8 cells appeared to be somewhat less effective than normal CD8 cells, but this did not reach significance. It is thus concluded that AITD CD4 cells respond specifically to TMc antigen. CD4 production of IFN gamma appears to be suppressed by CD8 cells activated with antigen and the CD8 cells appear to be involved in the regulation of IFN gamma production by the CD4 cells.