Disclosed are: a lactic acid bacterium belonging to Lactobacillus kunkeei, the bacterium having a higher IgA production inducing activity than that of Lactobacillus strain GG (ATCC53103), and a lower mitogenic activity and a lower IL-2 production inducing activity than those of Listeria strain EGD； and a food composition, a pharmaceutical composition, a cosmetic composition, an immunostimulant for preventing the infection by pathogens or viruses that invade through the respiratory or esophageal mucosa, and an intestinal immunostimulant for preventing or alleviating food poisoning, each of which contains the lactic acid bacterium or treated cells of the lactic acid bacterium.
