IgM cold-reactive lymphocytotoxin from sera in patients with sarcoidosis

Cold-reactive lymphocytotoxin (CLT) in the sera of patients with sarcoidosis was investigated by a complement-dependent 51Cr-release cytotoxicity assay. CLT activity was present in 19 out of 34 active sarcoidosis patients, but absent from all 6 resolved sarcoidosis patients and from 19 out of 20 healthy control subjects. CLT activity was not correlated with age or sex, degree of lymphopenia, presence of anergy, or with other clinical parameters, but was correlated with the activity of the disease. Lymphocytotoxic activity was greatest at 15 degrees C and negligible at 4 degrees C and 37 degrees C. The CLT in sarcoidosis sera had higher reactivity to B-lymphocytes than to T-lymphocytes. The CLT purified from sarcoidosis serum was identical with the antibody of IgM class. It was cytotoxic for B-lymphocytes but not reactive to T-lymphocytes. These results suggest that an IgM cold-reactive lymphocytotoxin exists in the sera of patients with active sarcoidosis.