Immune response of patients with rheumatoid arthritis during cyclophosphamide treatment

The immune response was studied in 21 patients with rheumatoid arthritis. Eleven had been randomly assigned to receive cyclophosphamide, 50 to 75 mg/day, and 10 to receive a placebo. Immunologic responsiveness was assessed by delayed hypersensitivity skin testing, immunoglobulin levels, in vitro lymphocyte blastogenesis and the primary immune response. All patients had elevated levels of IgG, normal or low IgA and IgM. Delayed hypersensitivity and in vitro lymphocyte blastogenic responses after immunization with the primary antigens Keyhole limpet hemocyanin and the amino acid copolymer (GLAT) were normal. Keyhole limpet hemocyanin and GLAT hemagglutinin titers were lower than normal due to decreased IgG and IgM formation. Treatment for 8 weeks with cyclophosphamide, 50 to 75 mg/day, did not alter the clinical status of the patients and had no detectable effect on their immune reactivity.