Roles of CD122+ Cells in Resistance against Neospora caninum Infection in a Murine Model

概要

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Innate cells, such as natural killer (NK) cells and NKT cells, play essential roles as primary effector cells at the interface between the host and parasite until adaptive immunity is established. The roles of NK and NKT cells in defense against Neospora caninum have not been well clarified. Because CD122 (interleukin-2 receptor beta chain) is expressed on NK and NKT cells, these cells were depleted by treatment with an anti-CD122 monoclonal antibody (mAb, TM-β1) in vivo. The parasite burden in the brain of mice was promoted by treatment with anti-CD122 mAb. However, there was no significant difference in the infection rates between controls and mice treated with anti-asialoGM1 antibody to deplete NK cells. Activation of CD4+ T cells was suppressed in mice treated with anti-CD122 mAb compared with controls and mice treated with anti-asialoGM1 antibody. On the other hand, depletion of CD122+ cells or NK cells did not affect the number of activated CD8+ T cells, dendritic cells and B cells following N. caninum infection. These results indicate that CD122+ cells (probably NKT cells) play a crucial role in host defense by activating CD4+ T cells against N. caninum infection.