Neutrophil (PMN) dysfunction occurs in HIV infection. Leukotrienes (LT) are mediators derived from the 5-lipoxygenase (5-LO) pathway that play a role in host defense and are synthesized by PMN. We investigated the synthesis of LT by PMN from HIV-infected subjects. There was a reduction (4.0+/-1.3% of control) in LT synthesis in PMN from HIV-infected compared with normal subjects. This was associated with reduced expression of 5-LO-activating protein (31.2+/-9.6% of normal), but not of 5-LO itself. Since HIV does not directly infect PMN, we considered that these effects were due to reduced release of cytokines, such as granulocyte colony-stimulating factor (G-CSF). We examined the effect of G-CSF treatment (300 microgram daily for 5 d) on eight HIV-infected subjects. PMN were studied in vitro before therapy (day 1) and on days 4 and 7. LTB4 synthesis was increased on day 4 of G-CSF treatment, and returned toward day 1 levels on day 7. 5-LO and 5-LO-activating protein expression were increased in parallel. As a functional correlate to this increase in PMN LT synthesis by G-CSF, we examined the effects on killing of Cryptococcus neoformans. Anticryptococcal activity of PMN from HIV-infected subjects was less than that of PMN from normal subjects. G-CSF treatment improved fungistatic activity of PMN. This increase in antifungal activity was attenuated by in vitro treatment with the LT synthesis inhibitor, MK-886. In conclusion, PMN from HIV-infected subjects demonstrate reduced 5-LO metabolism and antifungal activity in vitro, which was reversed by in vivo G-CSF therapy.