According to Casey Adams Ph.D., probiotics play a role in 70-80% of our immune response. Probiotics stimulate everything from T-cells to macrophages. Probiotics also activate cytokines and phagocytic cells to coordinate the immune response.
As in another study done by the Royal Society of Medcine in UK, 90% of infections & diseases are contracted via our Gastro-intestinal Tract (GI Tract). This further proves the imprtance that Probiotics play in our lives in our Immunity.
Current studies on the Microbiome of our GI tract by BIO E in Japan would reveal the co-relation between the type of bateria strains, it's DNA & in our own DNA interaction & Immunity.