Resistant mice lacking interleukin‐12 become susceptible to Trypanosoma cruzi infection but fail to mount a T helper type 2 response

• Published in: Immunology 2003-02, Vol.108 (2), p.230-237
• Main Authors: Galvão Da Silva, Ana Paula, Jacysyn, Jacqueline F., Abrahamsohn, Ises De Almeida
• Format: Article
• Language: English
• Subjects: Acute Disease; Animals; Antibodies, Protozoan; Cells, Cultured; Chagas Disease - immunology; Disease Susceptibility; Female; Interferon-gamma - biosynthesis; Interleukin-10 - biosynthesis; Interleukin-12 - genetics; Interleukin-12 - immunology; Interleukin-4 - biosynthesis; Mice; Mice, Inbred C57BL; Mice, Knockout; Nitric Oxide - biosynthesis; Original; Parasitemia - immunology; Th2 Cells - immunology; Trypanosoma cruzi - immunology; Tumor Necrosis Factor-alpha - immunology
• ISSN: 0019-2805; 1365-2567
• DOI: 10.1046/j.1365-2567.2003.01571.x

Summary Interleukin‐12 (IL‐12) is essential to resistance to Trypanosoma cruzi infection because it stimulates the synthesis of interferon‐γ (IFN‐γ) that activates macrophages to a parasiticidal effect. Investigation of mice deprived of IL‐12 genes (IL‐12 knockout mice) has confirmed the important role of IL‐12 and IFN‐γ in controlling parasitism in T. cruzi infection. However, it has not yet been addressed whether a shift towards a T helper type 2 (Th2) pattern of cytokine response occurred in these mice that might have contributed to the aggravation of the infection caused by IL‐12 deprivation. We examined the course of T. cruzi (Y strain) infection and the regulation of cytokine responses and nitric oxide production in C57BL/6 IL‐12 p40‐knockout mice. The mutant mice were extremely susceptible to the infection as evidenced by increased parasitaemia, tissue parasitism and mortality in comparison with the control C57BL/6 mouse strain (wild‐type) that is resistant to T. cruzi. A severe depletion of parasite‐antigen‐specific IFN‐γ response, without an increase in IL‐4 or IL‐10 production, accompanied by reduced levels of nitric oxide production was observed in IL‐12 knockout mice. We found no evidence of a shift towards a Th2‐type cytokine response. In IL‐12 knockout mice, the residual IFN‐γ production is down‐regulated by IL‐10 but not by IL‐4 and nitric oxide production is stimulated by tumour necrosis factor‐α. Parasite‐specific immunoglobulin G1 antibody levels were similar in IL‐12 knockout and wild‐type mice, whereas IL‐12 knockout mice had much higher levels of immunoglobulin G2b.