Haemophilus ducreyi causes the sexually transmitted disease chancroid, which facilitates HIV-1 transmission. Skin biopsies were obtained from subjects experimentally infected with H. ducreyi to study the evolution of the immune response and immunophenotypes relevant to transmission of HIV-1. Compared with peripheral blood, there was an enrichment of T cells and macrophages after 48 h of infection in the skin. Neutrophils became the predominant cell type by 7-9 days. By immunohistochemistry, macrophage-inflammatory protein-1alpha was not present early in infection, but was abundant at later stages. RANTES was present throughout the papular and pustular stages of experimental infection, but not present in uninfected control skin. Stromal cell-derived factor-1 was present at low levels in all samples examined. Macrophages in lesions had significantly increased expression of CCR5 and CXCR4 compared with peripheral blood cells, and CD4 T cells had significant up-regulation of CCR5. The magnitude of increased expression of these receptors was not replicated when PBMCs were incubated with H. ducreyi or H. ducreyi lipooligosaccharide in vitro. Together with the disruption of mucosal and skin barriers, the presence of cells with up-regulated HIV-1 coreceptors in H. ducreyi-infected lesions may provide an environment that facilitates the acquisition of R5 (CCR5), X4 (CXCR4), and dual-tropic HIV-1 strains.