A hypothesis concerning the mechanism whereby chloroquine phosphate and
hydrpxychloroquine sulfate are therapeutically active in rheumatoid arthritis is presented,
based on in vitro data that (1) utilize drug concentrations not higher than those clinically
achievable, and (2) might explain mechanisms that may be applicable in treated rheumatoid
arthritis patients. Simple assay systems were used: normal human peripheral blood
mononuclear cells were cultured, stimulated with various nonspecific agents, and assayed …