Figure 2.

A T helper 1 (Th1)-type response in BALB/c mice, which had been infected with low doses of Leishmania major, was already established 4 weeks after infection. Single-cell suspensions from the popliteal lymph nodes of individual mice in the designated groups which had been infected with 1 × 10² (striped bars), 1 × 10³ (dotted bars) or 1 × 10⁶ (open bars) of L. major were prepared 4 weeks after infection. The cells were cultured in triplicate for 72 hr in the presence of soluble leishmanial antigen (SLA) and X-ray-irradiated splenocytes from syngenic mice as antigen-presenting cells (APC). After culture, the supernatants were collected and assayed for interferon-γ (IFN-γ) and interleukin (IL)-4 using an enzyme-linked immunosorbent assay (ELISA). Each bar represents the average ± standard error of the mean (SEM) for six mice per group. *P<0·001 compared with the group of mice infected with 1 × 10⁶ parasites.