Relation between lymphocytotoxic antibodies, anti-DNA antibodies and a common anti-DNA antibody idiotype PR4 in patients with systemic lupus erythematosus, their relatives and spouses.

Forty-two patients with systemic lupus erythematosus (SLE), 65 of their healthy relatives and 20 spouses were studied for the presence of lymphocytotoxic antibodies (LCA), anti-lymphocyte antibodies (ALA), antibodies to DNA and a common idiotype (Id) PR4. Seventy-one per cent of the patients had positive levels of LCA, and in 34% the PR4 Id was detected; normal levels were found in their families. Anti-PR4, an anti-Id, failed to block the lymphocytotoxic activity in those nine patients who both carried the Id and had LCA. This indicates that the Id was not present on LCA. There was no correlation between anti-DNA antibodies and LCA, suggesting that different mechanisms are involved in their expression.