Effect of Bifidobacterium infantis on Interferon-gamma-induced keratinocyte apoptosis: a potential therapeutic approach to skin immune abnormalities

Current management of atopic dermatitis is mainly directed to the reduction of cutaneous inflammation. Since patients with atopic dermatitis show abnormalities in immunoregulation, a therapy aimed to adjust their immune function could represent an alternative approach, particularly in the severe form of the disease. Indeed, T-lymphocytes constitute a large population of cellular infiltrate in atopic/allergic inflammation and a dysregulated T-cell induced keratinocyte apoptosis appears to be an important pathogenetic factor of the eczematous disease. In recent years, attention has been focused on the interaction between host and probiotics which may have anti-inflammatory properties and immunomodulatory activities. The aim of the present work is to investigate the effect of a selected probiotic extract, the Bifidobacterium infantis extract, on a human keratinocyte cell line (HaCaT) abnormal apoptosis induced by activated-T-lymphocyte. An in vitro model of atopic dermatitis was used to assess the ability of the probiotic extract to protect HaCaT from apoptosis induced by soluble factors (IFN-gamma and CD95 ligand) released by human T-lymphocytes in vitro activated with anti-CD3/CD28 mAbs or Phytohemoagglutinin. Evidence is given that the bacterial extract treatment was able to totally prevent T lymphocyte-induced HaCaT cell apoptosis in vitro. The mechanism underlying this inhibitory effect has been suggested to depend on the ability of the bacterial extract to significantly reduce anti-CD3/CD28 mAbs and mitogen-induced T-cell proliferation, IFN-gamma generation and CD95 ligand release. These preliminary results may represent an experimental basis for a potential therapeutic approach mainly targeting the skin disorders-associated immune abnormalities.