Screening of Immune-Active Lactic Acid Bacteria

Immune modulation by probiotics is a growing area of interest in both clinical and space medicine. While lactic acid bacteria (LAB) are known for their potential to support immune function, their specific effects on immune cell proliferation and cytokine production remain underexplored. Prior research has shown that certain LAB strains can influence immune responses, but gaps remain in understanding which strains are most effective and under what conditions. No prior work had resolved the comparative immune-modulating effects of different LAB cell wall extracts. This uncertainty drove the need for a systematic screening of multiple LAB strains. The study aimed to address this knowledge gap by examining the immune effects of various LAB cell wall extracts. The focus was on identifying which strains could promote immune cell proliferation and TH1 cytokine production. This approach could help in selecting suitable probiotics for use in extreme environments like space. The findings may contribute to the development of probiotic-based interventions for immune support.

The study aimed to evaluate the immune-modulating potential of lactic acid bacteria (LAB) cell wall extracts. Specifically, the researchers sought to determine which LAB strains could enhance immune cell proliferation and TH1 cytokine production. They focused on ten different LAB strains commonly used in probiotics. The goal was to identify strains suitable for use in space food to maintain astronaut immunity. The study also aimed to assess how these extracts affect immune cell behavior in vitro. By comparing the effects of various LAB strains, the researchers hoped to find candidates with strong immune-stimulating properties. The motivation was to develop probiotics that could support immune health in extreme environments. This could also have broader applications for general immune support in everyday life.

The researchers selected ten LAB strains and cultured them to reach a concentration of 7-10 Log CFU/mL. Cell wall extracts were prepared from each strain following a standardized sub-culturing and growth protocol. Immune cell proliferation was measured using BALB/c mouse splenocytes and mesenteric lymphocytes. Cytokine production was analyzed to determine the effects on TH1 and TH2 cytokines. The study used in vitro cell culture techniques to assess immune responses. No immune-inhibiting effects were observed across the tested strains. The focus was on comparing the immune-stimulating effects of each LAB extract. The researchers used standardized cell culture conditions to ensure consistency in results.

Among the ten LAB cell wall extracts tested, most induced immune cell proliferation except for L. plantarum and L. delbruekii. The extracts increased TH1 cytokine (IFN-γ) production more than TH2 cytokine (IL-4) production. Four LAB strains—L. acidophilus, L. bulgaricus, L. casei, and S. thermophiles—showed the strongest effects on both cell proliferation and TH1 cytokine production. No inhibition of immune cell proliferation was observed in any of the tested extracts. The results suggest that these four strains have significant immune-modulating potential. The study found no evidence that any of the extracts suppressed immune cell activity. The findings indicate that these LAB strains could be effective in supporting immune function. These results may inform the development of probiotics for use in space and everyday environments.

The study found that four LAB strains—L. acidophilus, L. bulgaricus, L. casei, and S. thermophiles—showed strong immune-modulating effects. These strains promoted both immune cell proliferation and TH1 cytokine production. The results suggest that these LAB could be suitable for use as probiotics in space food. The findings may also have applications for general immune support in normal life. The authors propose that these strains could help maintain immunity and homeostasis in extreme environments. The study did not find evidence that any of the tested LAB extracts inhibited immune cell activity. The researchers suggest that these LAB strains could be further evaluated for use in probiotic formulations. The findings may contribute to the development of targeted immune-supporting probiotics.