Effects of Supernatants of Peripheral Blood Mononuclear Cells Stimulated by Thyroid Microsomal Antigen on Thyrocyte HLA-DR Expression in vitro

Abstract

Supernatants of 5 day cultures of peripheral blood mononuclear cells (PBMC) stimulated by thyroid microsomal antigens (TMA), and liver microsomal antigens (LMA) have been utilized to induce HLA-DR expression on human thyroid epithelial cells (TEC). The PBMC were obtained from 8 normal control persons and 13 patients with autoimmune thyroid disease (AITD) (7 Graves' disease and 6 Hashimoto's thyroiditis). The TEC HLA-DR expression was measured by an enzyme-linked immunosorbent assay (EL1SA) technique. TEC HLA-DR expression was calculated as follows: (experimental optical density -control optical density) x 10³; TEC HLA-DR index: % HLA-DR expression of IFNγ 100 U/ml stimulation; and stimulation index (SI): TEC HLA-DR expression index induced by PBMC supernatants with antigen stimulation/TEC HLA-DR expression index induced by PBMC supernatants without antigen stimulation ± 100. Supernatants without antigen stimulation from both normal control subjects and patients were able to induce TEC HLA-DR expression only minimally: 36.7 ± 32.6 (mean ± SD) TEC HLA-DR index for normal controls and 21.3 ± 15.5 TEC HLA-DR index for AITD (not significant). The SI curves of both TMA and LMA were significantly different between control and AITD using two-way ANOVA test (Plt;0.01). TMA-stimulated PBMC supernatants from the patients increased TEC HLA-DR expression when compared to basal level using paired t-test; TMA I ng/ml, SI 179 ± 99, p < 0.05. On the other hand, TMA-stimulated PBMC supernatants from normal controls decreased TEC HLA-DR expression; TMA 1 ng/ml, SI 78 + 23, p< 0.05; TMA 10 ng/ml, SI 69 ± 23, P< 0.01; TMA 100 ng/ml, SI 69 ± 35, p< 0.05. In contrast, LMA-stimulated PBMC supernatants from patients neither increased nor decreased TEC HLA-DR expression compared to basal level. While IFNfM-indueed TEC HLA-DR expressiona was completely suppressed by anti-human IFNy antibody (98 ± 2%), PBMC supernatant-induced TEC HLA-DR expression was less completely suppressed when anti-human IFNγ antibody was added to the cultures (77 ± 4%) (P<0.01 V.S. IFNγ). These results indicate that TMA stimulated PBMC from patients with AITD to secrete lympokine(s), presumably mostly IFNγ, which then lead to TEC HLA-DR expression. This phenomenon may reflect organ specific autosensitization of PBMC. Thus sensitized T lymphocytes from patients with AITD have the capacity to secrete such cytokines after stimulation with specific thyroid antigen, thus resulting in TEC HLA-DR expression. On the other hand, PBMC from normal controls did not have this capacity, which was reflected by the absence of sensitization to TMA and LMA.

Key Words:

• Autoimmune thyroid disease
• thyrocyte HLA-DR expression
• peripheral blood mononuclear cells (PBMC)
• thyroid microsomal antigen