This invention focuses on the effect and influence on promotion of IL-12 production from mice spleen cells by the cultivation conditions of Lactobacillus. The factors of immune regulating activity relating to the above Lactobacillus have been found, which is especially related to the pH of culture broth, and thus this invention is accomplished.致力研究乳酸菌的培養條件對於小鼠脾臟細胞之IL-12的產生具促進效果及影響。結果發現與上述乳酸菌與免疫機能調節活性相關的因子,特別是培養液的pH與免疫機能調節活性大有關聯,而完成本發明。