Interleukin-6 Deficiency Influences Cytokine Expression in Susceptible BALB Mice Infected with Leishmania major but Does Not Alter the Outcome of Disease

Since interleukin-6 (IL-6) may promote Th2 responses, we infected BALB IL-6-deficient (IL-6(−/−)) mice with Leishmania major. There was not a significant difference between the courses of infection (lesion size and parasite burden) in IL-6(−/−) and wild-type mice, but IL-6(−/−) mice expressed lower levels of Th2- and Th1-associated cytokines.