Impaired autologous mixed lymphocyte reaction with normal concanavalin A-induced suppression in adult polymyositis/dermatomyositis.

Polymyositis/dermatomyositis (PM/DM) is an autoimmune disorder of unknown aetiology. In order to study whether immunoregulatory abnormalities might be involved in this autoimmune state, we investigated the autologous mixed lymphocyte reaction (AMLR) and concanavalin A-induced suppressor cell function (Con A-induced suppression) in adult patients with primary PM/DM. We found the AMLR to be significantly depressed in patients; responsiveness could not be enhanced by increasing the numbers of non-T stimulator cells in culture, nor by varying the day on which cultures were harvested. Con A-induced suppression of T cell proliferative responses to mitogenic stimuli was normal. These findings implicate abnormal immunoregulation in the pathophysiology of PM/DM. Further, the dissociation of AMLR reactivity from Con A-inducible suppression suggests that events important for immunoregulatory competence may occur in the AMLR culture, despite the absence of an observed proliferative response.