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The Influence of Immunosuppressive Acidic Protein on the Activity of Peripheral K-Lymphocytes in Subacute Thyroiditis

Second Department of Internal Medicine, Department of Bacteriology (K. T.), Tohoku University School of Medicine Sendai, Japan

Address requests for reprints to: H. Fukazawa, M.D., Second Department of Internal Medicine, Tohoku University School of Medicine, 1–1 Seiryo-cho, Sendai City 980, Japan.

We previously reported that immunosuppressive acidic protein (IAP), an ₁-acid glycoprotein, is increased during the acute phase of subacute thyroiditis (SAT). In this study we measured the percentage and absolute number of peripheral K-cells using a plaque-forming cell technique to investigate immunological abnormalities associated with SAT. Additionally, we investigated the relationship between IAP and peripheral K-cell activity.

In normal controls, a sex-related difference in the percentage of K-cells among total lymphocytes was present; the percentage was significantly lower in women (mean ± SD, 5.0 ± 2.0%; n = 12; P < 0.01) than in men (8.4 ± 2.9%; n = 13). However, there was no difference (0.153 ± 0.073 x 10⁹/L in five females; 0.173 ± 0.054 x 10⁹/L in seven males) in the absolute number of peripheral K-cells.

During the acute phase of SAT, the percentage (2.4 ± 1.9% in 16 females; 2.7 ± 1.0% in 3 males) and absolute number (0.058 ± 0.048 x 10⁹/L in 11 females) of K-cells were significantly lower than those in normal controls. These values returned to normal during the recovery phase, although their mean values were still lower than those in normal controls.

In female patients with Graves' disease, the percentage (2.2 ± 1.8% in 11 females) and absolute number (0.038 ± 0.033 x 10⁹/L in 11 females) of K-cells were significantly lower than those in normal controls; in male patients, the percentage (4.2 ± 2.7% in 5 males) was lower than that in normal controls, but the absolute number (0.136 ± 0.114 x 10⁹/L) of K-cells was not significantly different.

Serum IAP values during the acute phase of SAT showed a significant negative correlation with the percentage of K-cells (r = –0.66; P < 0.01). The number of K-cells from a normal subject decreased significantly when these lymphocytes were incubated with sera from patients with SAT, and the mean inhibition rate of K-cells by serum samples from 13 SAT patients during the acute phase was higher than that during the recovery phase (68.0 ± 21.0 vs. 38.0 ± 23.0%; P < 0.01). Purified IAP inhibited the activity of K-cells from normal subjects dose dependently.

These results suggest that 1) there may be inhibitory factors for the antibody-dependent cell-mediated cytotoxicity of peripheral K-cells in the serum of patients with SAT, and 2) IAP may be one of these inhibitory factors.

Received March 30, 1989.