Papel do fator de Necrose Tumoral Alfa (TNF-α) na resposta imune celular e humoral durante a infecção por Neospora caninum

Abstract

The protozoan parasite Neospora caninum has been associated to abortions in cattle since the early 1990 s, and the infection leads to major economic impact to the segment. TNF-α is a proinflammatory cytokine produced quickly during the acute phase of infection, playing an important role in the immune response against various pathogens. Given the importance of this cytokine during acute infectious processes, we here aimed to verify the role of TNF-α during N. caninum infection. Therefore, we analyzed the cellular and humoral immune response using C57BL/6 wild type (WT) and genetically deficient mice in receptor 1 of TNF (TNFR1-/-), infected with N. caninum tachyzoites of the Nc-1 strain. We found an increase in susceptibility of TNFR1-/- mice, evidenced by higher mortality and increased parasite burden, in an IL-12 and IFN- independent mechanism. We also observed that TNF- is required for regular IgG subclass production. TNFR1-/- mice presented enhanced serum concentration of IgG2a subclass, while IgG1 production was hampered, if compared to WT mice. Gathering this information, we conclude that TNF-α presents an important role in host resistance and IgG subclass production against infection by the protozoan N. caninum.