To investigate the role of Cryptococcus in the immune system of immunocompetent patients with pulmonary cryptococcosis (PC) by analysing the dynamic changes of patients’ immune status before and after antifungal therapy.

The level of the serum interferon-γ (IFN-γ) and interleukin (IL)-2, -4, -10 and -12 was measured before and after 6-months of treatment. Peripheral blood samples were obtained from 30 immunocompetent PC patients and 30 age- and gender-matched healthy controls. Peripheral blood mononuclear cells (PBMCs) were isolated and incubated with recombinant human IL-12 (rhIL-12) for 48 h. Then the concentrations of IFN-γ and IL-4 in the supernatant were analysed.

Baseline serum IFN-γ level was significantly lower in the PC patients as compared with the control group (P < 0.001). The serum IL-2 and IFN-γ of PC patients were significantly increased after appropriate treatments (P < 0.05 and P < 0.001 when compared to their baseline levels). The productions of IFN-γ in the culture supernatant of PBMCs showed no significant difference between the control and PC patients both before and after antifungal treatments. RhIL-12 is a potent stimulus for IFN-γ production. Culture PBMCs collected from PC patients before treatments had a smaller increase of IFN-γ production in the present of rhIL-12 than the control (P < 0.01); PBMCs from PC patients completing 6-months of treatment showed a comparable increase of IFN-γ production by rhIL-12 stimulation to the control group.

In apparently immunocompetent patients with PC, a normalization of serum IFN-γ was achieved after recovery from infection. This suggests that Cryptococcus infection per se can suppress the immune system and its elimination contributes to the reestablishment of an immune equilibrium.