NK cells are the main components of host-nonspecific cell-mediated immunity

NK cells are the main components of host-nonspecific cell-mediated immunity, recognizing and helping to control a wide range of pathogens, including viruses, bacteria, and intercellular parasites. NK cells are activated by IL-12 that is produced by antigen-presenting cells, such as macrophages, DCs, and Langerhans cells. Here again, data suggest that the dialog between DCs and bacteria is key to controlling the immune effects of LAB beyond the GI tract. Koizumi demonstrated that feeding mice with Lactobacillus pentosus significantly enhances NK activity of spleen cells and induced NK1.1-positive NK and NK T cells to produce interferon (IFN)-g. Viagra online canadian pharmacy at

The increase in IFN-g production did not occur through direct action of L pentosus on NK cells but was dependent on IL-12 produced by CD11c⁺ DCs following a toll-like receptor (TLR) 2- and/or TLR4-dependent interaction between the DC and LAB. Strains of LAB differ greatly in their ability to induce high levels of IL-12 in human DCs and consequently DC-dependent IFN-g production by NK cells.

Alveolar macrophages provide the first line of defense against organisms that reach the lower airways. In addition to their phagocytic function, alveolar macrophages can synthesize and release various protein and lipid mediators on contact with pathogens or pathogenic substances. LAB have been well characterized in terms of an ability to induce cytokine production following contact with mononuclear phagocytes.

The ability of orally administered L casei to dose-dependently enhance the phagocytic activity of alveolar macrophages likely contributes to the accelerated recovery of the innate immune response and improved outcomes following Streptococcus pneumoniae respiratory infection in malnourished mice and in young mice infected with Pseudomonas aeruginosa. Here again, the suggestion is that stimulation of the GALT leads to a general enhancement or priming of the innate immune response in the airway.