Antibody-dependent cell-mediated cytotoxicity (ADCC) of human peripheral blood leukocytes using sheep red blood cells　as target cells　Part II. ADCC and erythrophagocytosis of peripheral leukocytes in patients with Sjogren's syndrome or rheumatoid arthritis

Antibody-dependent cell-mediated cytotoxicity (ADCC) and antibody-dependent erythrophagocytosis (ADEP) of peripheral blood leukocytes in patients with Sjogren's syndrome (SjS) or rheumatoid arthritis (RA) were investigated using (51)Cr-labelled sheep red blood cells as target cells. The Lymphocytes (phagocyte depleted fraction, PDF) in healthy controls showed higher ADCC activities (58.6±9.9%) than the phagocyte-contaminated crude lymphocyte fraction (CLF) (49.1±10.9%). There was no statistically significant difference between the ADCC activities of PDF in patients with SjS (55.9±13.5%) or RA (58.8±9.6%) and those in healthy controls, although decreased ADCC activity was observed in some patients with SjS. ADCC activities of CLF in patients with SjS (61.2±14.3%) or RA (59.3±6.9%) were significantly higher than those of CLF in healthy controls. Decreased ADEP activity of monocytes in CLF was demonstrated in patients with SjS (17.9±9.4%) compared with healthy controls (37.2±10.6%), and increased ADCC activity of CLF in patients with SjS was dependent on decreased ADEP activity of contaminating monocytes. Decreased ADEP activity of monocytes in patients with RA was also suggested by these results. It was speculated that the decreased Fc-receptor function of peripheral blood monocytes, demonstrated in these patients, had originated from aberrant cell-mediated immunity in these diseases, since these Fe-receptor functions in patients with SjS did not correeate with the following conditions: associated diseases, erythrocyte sedimentation rate, titer of serum rheumatoid factor, lymphocyte count of peripheral blood, or treatment with anti-inflammatory drugs including prednisolone.