Although the participation of CD4+ Th1 lymphocytes with IFN-γ production has been demonstrated in mice protected against L. (L.)amazonensis infection (37, 38), it is important to emphasize that the immune responses induced against L. (L.) amazonensis have shown a distinct pattern from that described for L. (L.) major. While mice that are resistant or susceptible to infection with L. (L.) major exhibit immune responses polarized to Th1 and Th2, respectively, susceptibility to L. (L.) amazonensis cannot be correlated to an increased Th2 response (39). The gene discussed is IFNG; the disease is infection.