Mechanisms of immunity to Ehrlichia muris: a model of monocytotropic XXXX .

@entity12431 @entity39 @entity19 @entity5 @entity281 @entity1961 @entity915
Ehrlichia species can cause life-threatening @entity281 . Mechanisms of protective immunity were examined in an Ehrlichia muris @entity19 model of monocytotropic @entity12431 . C57BL/6 @entity19 possessed strong genetic resistance to E. muris of an undetermined mechanism. CD8 T lymphocytes were particularly important, as revealed by 81% fatalities for E. muris-infected, major histocompatibility complex class I gene knockout @entity19 compared with no deaths for wild-type C3H @entity19 . Moreover, 80% of C3H @entity19 depleted of CD8 and @entity1961 cells died of E. muris @entity281 compared with only 44% of @entity1961 cell-depleted @entity19 . CD8 T lymphocytes were demonstrated for the first time in an Ehrlichia @entity281 to exhibit cytotoxic T-lymphocyte activity against Ehrlichia-infected target cells. Both gamma interferon and @entity5 @entity39 factor were shown to play synergistic roles in protective immunity in vivo for the first time, as demonstrated by 75% fatalities when both cytokines were neutralized compared with minimal mortality when they were depleted separately. Passive transfer of antibodies, but not Fab fragments, to E. muris protected C3H/ @entity915 @entity19 against @entity281 . The mechanism of increased susceptibility (22% lethality) of C57BL/6 major histocompatibility complex class II gene knockout @entity19 and @entity1961 cell-depleted C3H @entity19 (i.e., through a gamma interferon or antibody mechanism), as well as the more important role of CD8 T lymphocytes (in the form of cytotoxic T-lymphocyte activity and/or gamma interferon production), remains to be elucidated. Protective immunity against monocytotropic E. muris is mediated by a combination of CD8 and @entity1961 T lymphocytes, gamma interferon, @entity5 @entity39 factor alpha, and antibodies.
