Disparate findings have been reported as to whether human immunodeficiency virus (HIV) affects cytokine production by macrophages (MA). We investigated production of different cytokines and of macrophage inflammatory protein (MIP)-1alpha by HIV-1Ba-L-or HIV-1Ada-infected blood-derived MA. Relative to controls, only MIP-1alpha levels increased twofold to > 10-fold in supernatants 2 to 3 weeks postinfection (PI), at the time of maximum virus production; levels of the other chemokines (RANTES, interleukin (IL)-8) and cytokines (IL-1alpha, IL-3, IL-6, granulocyte-macrophage colony-stimulating factor (GM-CSF), G-CSF, tumor necrosis factor (TNF)-alpha, transforming growth factor (TGF)-beta1) investigated were not affected. MIP-1alpha mRNA signal assessed by reverse transcriptase-polymerase chain reaction (RT-PCR) was, however, only occasionally greater in cells from infected cultures relative to controls. MIP-1alpha levels in supernatants remained in the same range as in control cultures when more than 10 mmol/L Zidovudine was added 24 hours PI, which indicates involvement of virus replication in the effect. Anti-MIP-1alpha antibody labeling identified a 10% to 25% subset of MA, strongly expressing HLA-DR and CD4, and also stained by anti-IL-6 and anti-TNF-alpha antibodies. Two weeks PI, dual staining showed that the majority of the 5% to 20% cells that were p24+ belonged to the MIP-1alpha+ population, which may define a MA subset capable to better sustain HIV replication. MIP-1alpha induced by HIV replication in MA might play a role in the pathophysiology of HIV infection; in impaired hematopoiesis; or as a CD4+ and CD8+ lymphocyte chemoattractant, by recruiting either or both HIV-susceptible and cytotoxic T lymphocytes to virus replication sites.