In vitro infection of equine peripheral blood mononuclear cells (PBMC) with the non-neuropathogenic EHV-1 strain RacL11 reduced the down-regulation of MHC class I expression [35], and increased interleukin10 (IL-10) secretion [36] and chemokine expression [37] compared to infection with the neuropathogenic strain Ab4. This evidence concerns the gene IL10 and infection.