Differential immunomodulating effects of inactivated probiotic bacteria on the allergic immune response

Bacterial stimulation plays an important role in modulating the allergic immune response. The aim of this study was to investigate the effects of inactivated probiotic Lactobacillus acidophilus and non-pathogenic Escherichia coli strain Nissle on the phenotype and function of T- and B-cells. Peripheral blood mononuclear cells from patients with grass-pollen allergy (n=10) and non-allergic patients (n=19) were co-stimulated with inactivated bacteria and grass-pollen allergen. Expression of CD23, CD80, CD86 and CD69 were analysed, and the intracellular production of interleukin-4 and interferon-gamma was measured by direct ex vivo flow cytometry after stimulation. Both bacteria induced a significant up-regulation of CD69 expression on T-lymphocytes (p=0.001). CD23 expression was significantly increased following stimulation with allergen (p=0.008), but reduced after stimulation with Lactobacillus and significantly reduced with E. coli plus allergen (p=0.029). CD80 expression was reduced after stimulation with Lactobacillus in the allergic group only (p=0.021). By contrast, CD86 expression was significantly increased after stimulation with Lactobacillus (p=0.049) and distinctly increased with E. coli in both groups (p=0.001). The cytokine patterns of CD69-positive T-lymphocytes from allergic patients showed a TH2-dominated response after allergen stimulation (interferon-gamma/interleukin-4-ratio 0.2), directed into a T-helper1-like response by stimulation with both types of bacteria (interferon-gamma/interleukin-4-ratios 1.5-2.0 in both groups). These data show that both types of bacteria modulate the allergic immune response by the alteration of CD23 and co-stimulatory molecule expression. Regarding cytokine production, the data suggest a differential response to both bacteria depending on the atopic state, but a clear promotion of T-helper1-dominated response in allergic donors.