Using a flow cytometric assay we investigated neutrophil-M.tuberculosis opsonophagocytosis and the impact of HIV-1-infected serum on this process. The mean (±SD) percentage of neutrophils internalising bacilli after 30 minutes incubation was significantly reduced by pre-treatment with anti-CD16 (18.2±8.1%, p<0.001) or anti-CD35 antibody (23.2±10.6%, p<0.05) versus anti-CD4 controls (29.9±8.1%). Blocking CD88 or CD11a did not affect internalisation. Using heat-inactivated serum, maximal internalisation was lower using HIV-1-infected serum versus HIV-1-uninfected. Using non-heat-inactivated serum, internalisation decreased more rapidly with sequential dilutions of HIV-1-infected versus HIV-1-uninfected serum. CONCLUSIONS: CD16 and CD35 are important for neutrophil internalisation of M.tuberculosis while HIV-1 infection adversely affects opsonophagocytosis.