Lactobacilluscasei reduces CD8+ T cell‐mediated skin inflammation

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Abstract
Probiotics, including Lactobacilli, have been postulated to alleviate allergic and inflammatory diseases, but evidence that they exert an anti‐inflammatory effect by immune modulation of pathogenic T cell effectors is still lacking. The aim of this study was to examine whether L. casei could affect antigen‐specific T cell‐mediated skin inflammation. To this end, we used contact hypersensitivity to the hapten 2,4‐dinitrofluorobenzene, a model of allergic contact dermatitis mediated by CD8+ CTL and controlled by CD4+ regulatory T cells. Daily oral administration of fermented milk containing L. casei or L. casei alone decreased skin inflammation by inhibiting the priming/expansion of hapten‐specific IFN‐γ‐producing CD8+ effector T cells. The down‐regulatory effect of the probiotics required the presence of CD4+ T cells, which control the size of the hapten‐specific CD8+ T cell pool primed by skin sensitization. L. casei cell wall was as efficient as live L. casei to regulate both the CHS response and the hapten‐specific CD8+ T cell response, suggesting that cell wall components contribute to the immunomodulatory effect of L. casei. This study provides the first evidence that oral administration of L. casei can reduce antigen‐specific skin inflammation by controlling the size of the CD8+ effector pool.

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