FIG. 2.

Cytokine secretion by spleen cells from S. mansoni-infected and infected-reinfected rats in response to in vitro antigen stimulation. Bars: ░⃞, infected rats; ▨, infected-and-reinfected rats. The secondary infection was performed at day 63 postinfection (represented by the arrow). Cells were stimulated with S. mansoni cercarial soluble antigens. Cytokine production was evaluated in 24-h culture supernatants for the measurement of IL-5, in 48-h culture supernatants for the measurement of IL-4, and in 72-h culture supernatants for the measurement of IFN-γ. The constitutive production (———) is that of uninfected animals. Panel a represents IL-4 secretion, and the constitutive production value is 7.8 ± 2.08 pg/ml. Panel b represents IL-5 secretion, and the constitutive production value is below the detection limit. Panel c represents IFN-γ production, and the constitutive production value is 1,050 ± 826 pg/ml. A significant increase in the secretion of IL-4 and IL-5 was observed after primary and secondary infections compared to uninfected rats (P < 0.05) at days 4, 7, 11, 21, 42, 65, 70, 84, and 91 for infected rats and days 70, 78, 84, and 91 for infected-reinfected rats. IFN-γ secretion was significant at day 21 postinfection (P < 0.05).