Homogenates derived from probiotic bacteria provide down-regulatory signals for peripheral blood mononuclear cells

Recently, probiotics have been under investigation for anti-inflammatory properties, especially in patients with atopic dermatitis and food allergy. Yet, the pharmacotherapeutic potential of the anti-inflammatory effect has not been documented. The present study aimed to establish the influence of non-viable, filtered bacterial homogenates on peripheral blood mononuclear cell proliferation, activation receptor expression and cytokine production. All bacterial homogenates inhibited both basal and phytohemagglutinin-stimulated peripheral blood mononuclear cell proliferation (PBMC). The suppression of PBMC proliferation by bacterial homogenates was further shown to be protein concentration-dependent. Also, the anti-proliferative potential of bacterial homogenates was comparable to the anti-proliferative effect of dexamethasone at 1 μmol/l. Moreover, Lactobacillus GG, Bifidobacterium Bb-12 and L. acidophilus homogenates inhibited the expression of CD25, CD69 and HLA-DR on phytohemagglutinin stimulated T lymphocytes. Bifidobacterium Bb-12 and L. acidophilus homogenates also inhibited IL2 and IL4 production. Our findings suggest that specific probiotic bacteria, or factors derived from them, may provide down-regulatory signals for peripheral blood mononuclear cell.