Neutralizing cytokine antibodies are found in healthy and diseased individuals, including patients treated with recombinant cytokines. Identification of CCR-5 as co-receptor for HIV has focused interest on CC chemokines and their potential therapeutic use. Chemokine-binding components in plasma of HIV-infected patients were therefore assessed by radioimmunoassay and radioreceptor assay. IgG from 4/505 HIV patients and 9/2000 healthy controls (p>0.05) bound rMIP-1alpha and rMIP-1beta, but not rRANTES. No other plasma factors bound the chemokines. The antibodies inhibited receptor binding of both chemokines. There was no association between presence of antibodies and disease stage or HIV progression rate. Three of 11 patients treated with rIL-2 developed IgG antibodies suppressing cellular binding and growth promotion of rIL-2. Hence, circulating factors, including antibodies MIP-1alpha/MIP-1beta, are uncommon in healthy individuals and HIV patients, and are apparently without prognostic significance. In contrast to earlier reports, IL-2 antibodies were found only in HIV patients treated with rIL-2.