The immune reinforcement of the probiotic lactic acid bacteria Lactobacillus acidophilus, Streptococcus thermophilus and Bifidobacterium bifidum was studied in RAW 264.7 cell line treated with diluted solution (dilution to $2^{5}$) of the supernatnats of lactic acid bacteria. RAW 264.7 cell line was used as a macrophage model to assess the effects of lactic acid bacteria on the production of nitric oxide (NO) and cytokine tumor necrosis factor (TNF)-$alpha$ and cell morphological changes. The production of NO and TNF-$alpha$ were largely affected by lactic acid bacteria in dose-dependent manner in 24 or 48 hr cultures and cell morphological changes were also largely affected by lactic acid bacteria. Especially Bifidobacterium bifidum differentially stimulated the production of NO and TNF-$alpha$. NO production was increased by Bifidobacterium bifidum 25 $mu$l/ml more than LPS (20 ng/ml) control, and TW-$alpha$ by Bifidobacterium bifidum 6.25 $mu$l/ml more than LPS (10 ng/ml) control. The in vitro approaches employed here should be useful in further characterization of the effects of lactic acid bacteria on systemic immunity.