Roles for NK Cells and an NK Cell-Independent Source of Intestinal Gamma Interferon for Innate Immunity to Cryptosporidium parvum Infection▿

AUTOR(ES)

Barakat, Farah M.

FONTE

American Society for Microbiology (ASM)

RESUMO

A gamma interferon (IFN-γ)-dependent innate immune response operates against the intestinal parasite Cryptosporidium parvum in T- and B-cell-deficient SCID mice. Although NK cells are a major source of IFN-γ in innate immunity, their protective role against C. parvum has been unclear. The role of NK cells in innate immunity was investigated using Rag2−/− mice, which lack T and B cells, and Rag2−/− γc−/− mice, which, in addition, lack NK cells. Adult mice of both knockout lines developed progressive chronic infections; however, on most days the level of oocyst excretion was higher in Rag2−/− γc−/− mice and these animals developed morbidity and died, whereas within the same period the Rag2−/− mice appeared healthy. Neonatal mice of both mouse lines survived a rapid onset of infection that reached a higher intensity in Rag2−/− γc−/− mice. Significantly, similar levels of intestinal IFN-γ mRNA were expressed in Rag2−/− and Rag2−/− γc−/− mice. Also, infections in each mouse line were exacerbated by treatment with anti-IFN-γ neutralizing antibodies. These results support a protective role for NK cells and IFN-γ in innate immunity against C. parvum. In addition, the study implies that an intestinal cell type other than NK cells may be an important source of IFN-γ during infection and that NK cells may have an IFN-γ-independent protective role.

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