IL2 and infection: On the other hand, feeding Ixodes ticks suppress Th1 responses against tick-borne LD spirochetes in mice (17), and the suppression of Th2 cytokines or the reconstitution of tumor necrosis factor alpha, interleukin-2 (IL-2), and gamma interferon (IFN-γ) after tick attachment reduces infection rates in disease-susceptible laboratory mouse strains (18, 19).