Facial nerve lesion response; strain differences but no involvement of IFN-gamma, STAT4 or STAT6.

Facial nerve lesions lead to a retrograde response characterized by activation of glia surrounding axotomized motoneurons and up-regulation of immunological cell surface molecules such as major histocompatibility complex (MHC) antigens. Cytokines, in particular interferon-gamma, are potent inducers of MHC expression and glial activation. We have here tested whether axotomy-induced activation is changed in transgenic mouse strains lacking components of the IFN-gamma signaling pathway, STAT4 or STAT6. No differences regarding astrocyte activation, ss2-microglobulin or MHC class I expression were discernible as compared to wild type controls. In contrast, there were conspicuous differences in the reaction between the examined wild type strains (C57BL/6J, BALB/c and 129/SvJ), suggesting considerable polymorphisms in the genetic regulation of these events, however, not involving IFN-gamma, STAT4 or STAT6.