PROBLEM TO BE SOLVED: To provide a lactic acid bacterium having a high promoting effect on IgA production, a food composition, pharmaceutical composition, cosmetic composition, immunostimulant for preventing infection against pathogens or viruses invading from the mucosa of the respiratory tract or esophagus, and intestinal immunity enhancer for preventing or alleviating food poisoning, which contain a lactic acid bacterium or a bacterial cell-treated product thereof.SOLUTION: According to the present invention, there is provided a lactic acid bacterium belonging to Lactobacillus kunkeei or an IgA production enhancer comprising a bacterial cell-treated product.EFFECT: Lactobacillus kunkeei has a higher production activity of IgA than Lactobacillus GG strain (ATCC 53103), and has a lower mitogenic activity and IL-2 production-promoting action than Listeria EGD strain.SELECTED DRAWING: None【課題】IgAの産生促進作用が高い乳酸菌の提供。並びに乳酸菌又はその菌体処理物を含有する食品組成物、医薬組成物、化粧品組成物、気道又は食道の粘膜から侵入してくる病原体又はウイルスに対する感染予防用の免疫賦活剤、及び食中毒の予防又は緩和用の腸管免疫賦活剤の提供。【解決手段】ラクトバチルス・クンキーに属する乳酸菌又はその菌体処理物を含有するIgA産生促進剤。【効果】ラクトバチルス・クンキーは、ラクトバチルスGG株(ATCC53103)よりIgAの産生促進作用が高く、且つリステリアEGD株よりマイトジェン活性及びIL-2産生促進作用が低い。【選択図】なし