Gut mucosal immunostimulation by lactic acid bacteria

The beneficial properties of lactic acid bacteria (LAB) on human health hav e been frecuently demonstrated. The interaction of LAB with the lymphoid ce lls associated to the gut to activate the mucosal immune system and the mec hanisms by which they can exert an adjuvant effect is still unclear, as wel l as if this property is common for ail the LAB. We studied the influence o f the oral administration of different genous of LAB such as Lactobacillus casei, L. acidophilus, L. rhamnosus, L. delbrueckii subsp. bulgaricus, L. p lantarum, Lactococcus lactis and Streptococcus thermophilus. We determined if the LAB assayed were able to stimulate the specific, the non-specific im mune response (inflammatory response), or both. We demonstrated that all th e bacteria assayed were able to increase the number of IgA producing cells associated to the lamina propria of small intestine. This effect was dose d ependent. The increase in IgA(+) producing cells was not always correlated with an increase in the CD4(+)T cell number, indicating that some LAB assay ed only induced clonal expansion of B cells triggered to produce IgA. Most of them, induced an increase in the number of cells involved in the inflamm atory immune response. CD8(+) T cell were diminished or not affected, with exception of L. plantarum that induced an increase at low dose. This fact w ould mean that LAB are unable to induce cytoxicity mechanisms. We demonstrated the importance in the selection of LAB to be used as gut mu cosal adjuvant. The different behaviours observed among them on the gut muc osal immune response, specially those that induce inflammatory immune respo nse, show that not all the LAB can be used as oral adjuvant and that the be neficial effect of them can not generalized to genous or specie. The immuno adjuvant capacity would be a property of the strain assayed.