Abnormal monocyte cytotoxicity and cyclic-AMP levels in systemic sclerosis.

Monocyte antibody-dependent cell-mediated cytotoxicity (ADCC) was compared to intrinsic cyclic-adenosine-monophosphate (cAMP) levels in 14 patients with systemic sclerosis. Depressed monocyte cytotoxicity was observed. Elevated cAMP levels (2-5 times) in resting monocytes were found in 5 patients; the rest had normal cAMP values. Monocyte ADCC was inversely correlated to cellular cAMP content (r = -0.6659, P less than 0.02). Scleroderma patients with high basal cAMP levels showed impaired responses to beta-adrenergic stimulation but not to prostaglandin E (PGE1) and histamine. Patients with normal basal cAMP levels showed no defect in beta-adrenergic responses. No close correlation between monocyte abnormality and clinical state was found.