In infants, faecal levels of total IgA and anti-poliovirus IgA during intake of a formula containing Bifidobacterium lactis BB-12 were significantly higher than those before intake.The increase in local IgA levels resulting from ingestion of the probiotic formula may contribute to enhancement of the mucosal resistance against gastrointestinal infections (Fukushima et al., 2011).
Van Baarlen et al. (2011) suggested on the basis of their clinical trial results, that consumption of L. casei CRL-431 may promote a shift in the Th1/Th2 balance towards a Th2 type and/or Th17 type, the latter consistent with the observed up-regulation of IL-17D (syn. IL-22) and IL-21. IL-15, IL-17D (IL-22), and IL-21 which are also involved in development of natural killer cells.
Note: Th1 type immune responses are more effective against intracellular pathogens (viruses and bacteria). Th2 responses are more effective against extracellular bacteria and parasites, and are involved in class switching of B-cell production of immunoglobulins to IgA, IgG1 and IgE. IgA is the immunoglobulin most important for protection of mucosal surfaces.
The study by Zhang et al (2018) utilised Lactobacillus casei CRL 431 in combination with two other strains of Lactobacillus and reported that subjects who consumed probiotics demonstrated a significantly higher level of IFN-γ in the serum (p < 0.001) and sIgA in the gut (p < 0.010) as compared to the placebo group and a significant higher level of serum IFN-γ (p < 0.001) and gut sIgA (p < 0.001) compared to their baseline test results. The authors reported that the study demonstrated that probiotics were safe and effective for fighting the common cold and influenza-like respiratory infections by boosting the immune system.
Research using four strains of Lactobacillus ( L. casei CRL431 was not tested) demonstrated that IL-1β expression was induced by L. helveticus and L. casei, but not by two other species of Lactobacillus.. IL-1 β plays an important role in the costimulation of T lymphocytes. This result is indicative of differences between strains in relation to effects on the immune system. Phagocytosis and bactericidal activity of cultured human macrophages against various pathogens, such as S. aureus, S. typhimurium, and E. coli, were increased by pretreatment with Lactobacillus (Rocha-Ramirez et al., 2017).
Bifidobacterium BB-12 has been reported by Meng et al., (2017) to reduce pro-inflammatory cytokines in healthy adults. The delivery matrix influences the immunomodulatory properties of BB-12, with the effects only observed when BB-12 was added to yoghurt after fermentation.
Mohan et al. (2008) conducted a double blind, placebo controlled randomized clinical study was performed on 69 preterm infants. In the probiotic group, orally treated with Bifidobacterium BB-12 faecal IgA was higher compared with the placebo group (p = 0.021).
Taken together, the experiments support the suggestion that probiotic strains of Lactobacillus, including Lactobacillus casei CRL 431 and Bifidobacterium BB-12 exert immunostimulatory effects that may be linked to the initial response to pathogens by human macrophages and an increase in IgA levels.
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