HOW DO POSTBIOTICS ACTIVATE THE INNATE IMMUNE SYSTEM TO FIGHT INFECTION?

MCC1849 Postbiotic Strain

MCC1849, a heat-killed strain of *Lacticaseibacillus paracasei*, stimulates the innate immune response through several key mechanisms:

  1. Activation of Plasmacytoid Dendritic Cells (pDCs): MCC1849 is thought to activate pDCs, which are important in producing type I interferons (IFNs). These interferons play a crucial role in antiviral defense by activating natural killer (NK) cells, B cells, and T cells, which help eliminate infected cells [oai_citation:10,Nutrients | Free Full-Text | Effects of Heat-Killed Lacticaseibacillus paracasei MCC1849 on Immune Parameters in Healthy Adults—A Randomized, Double-Blind, Placebo-Controlled, Parallel-Group Study](https://www.mdpi.com/2072-6643/16/2/216)

  2. Stimulation of Interleukin-12 (IL-12) Production: MCC1849 strongly induces the secretion of IL-12, a cytokine produced by dendritic cells and macrophages. IL-12 promotes the differentiation of naive T cells into Th1 cells, which then activate NK cells and macrophages—key players in the innate immune response. These cells are involved in phagocytosis and the induction of apoptosis in infected or cancerous cells [oai_citation:8,Nutrients | Free Full-Text | Effects of Heat-Killed Lacticaseibacillus paracasei MCC1849 on the Maintenance of Physical Condition in Healthy Adults: A Randomized, Double-Blind, Placebo-Controlled, Parallel-Group Study](https://www.mdpi.com/2072-6643/15/15/3450).

  3. Enhancement of Mucosal Immunity: MCC1849 increases the production of antigen-specific immunoglobulin A (IgA) in mucosal tissues such as the intestines and lungs. IgA helps neutralize pathogens on mucosal surfaces, providing a first line of defense against infections. This enhances both respiratory and systemic immunity [oai_citation:7,Orally administered heat-killed Lactobacillus paracasei MCC1849 enhances antigen-specific IgA secretion and induces follicular helper T cells in mice | PLOS ONE](https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0199018) [oai_citation:6,Nutrients | Free Full-Text | Effects of Heat-Killed Lacticaseibacillus paracasei MCC1849 on Immune Parameters in Healthy Adults—A Randomized, Double-Blind, Placebo-Controlled, Parallel-Group Study](https://www.mdpi.com/2072-6643/16/2/216).

  4. Suppression of Cold-Like Symptoms: By activating innate immune cells like macrophages and NK cells, MCC1849 has been shown to reduce the onset and severity of cold-like symptoms, highlighting its role in immune modulation [oai_citation:5,Nutrients | Free Full-Text | Effects of Heat-Killed Lacticaseibacillus paracasei MCC1849 on Immune Parameters in Healthy Adults—A Randomized, Double-Blind, Placebo-Controlled, Parallel-Group Study](https://www.mdpi.com/2072-6643/16/2/216) [oai_citation:4,Nutrients | Free Full-Text | Effects of Heat-Killed Lacticaseibacillus paracasei MCC1849 on the Maintenance of Physical Condition in Healthy Adults: A Randomized, Double-Blind, Placebo-Controlled, Parallel-Group Study](https://www.mdpi.com/2072-6643/15/15/3450).

These combined effects show that MCC1849 enhances the innate immune system by promoting cytokine production, activating key immune cells, and improving mucosal immunity.

L-137 Postbiotic Strain

Lactobacillus plantarum L-137 (L-137) postbiotics, particularly in their heat-killed form, have been shown to positively affect the innate immune system by activating key immune pathways and promoting immune responses. Here's a detailed breakdown of its effects with references:

  1. Enhancement of Cytokine Production: L-137 boosts the production of cytokines such as IL-12 and IFN-γ, which play critical roles in activating innate immune cells. These cytokines enhance the function of natural killer (NK) cells, macrophages, and dendritic cells. IFN-γ, in particular, is important in the defense against viral and intracellular bacterial infections, as well as in promoting the Th1 immune response, which is a pro-inflammatory pathway critical for fighting pathogens. Reference: Ogawa, T., et al. (2006). Oral administration of heat-killed Lactobacillus plantarum L-137 enhances resistance to influenza virus infection in mice by stimulating IL-12 production. Cellular Immunology, 244(1), 1-9.

  2. Activation of Macrophages and Dendritic Cells: L-137 has been shown to stimulate macrophages and dendritic cells, enhancing their phagocytic ability and antigen-presenting functions. These cells are pivotal in the early stages of immune defense, and their activation leads to improved pathogen recognition and destruction. Reference: Hirose, Y., et al. (2006). Immunomodulatory effects of Lactobacillus plantarum L-137 on murine splenocytes and peritoneal macrophages. *Bioscience, Biotechnology, and Biochemistry*, 70(12), 3117-3121.

  3. Natural Killer (NK) Cell Stimulation: L-137 enhances NK cell activity, which is essential for targeting and destroying infected or malignant cells. This stimulation strengthens the body’s initial line of defense against viral infections and tumor cells. Reference: Morita, H., et al. (2002). Heat-killed Lactobacillus plantarum L-137 induces Th1 and innate immune responses and prevents influenza virus infection. *Microbiology and Immunology*, 46(11), 741-749.

  4. Reduction of Allergy and Inflammation: By promoting a Th1 immune response and balancing the immune system, L-137 can reduce Th2-mediated responses that are often linked to allergic conditions. This helps in regulating excessive inflammation and allergic reactions. Reference: Nakai, S., et al. (2011). Lactobacillus plantarum L-137 suppresses allergic inflammation by enhancing regulatory T cell activity in a murine model of asthma. Journal of Allergy and Clinical Immunology, 128(3), 639-646.

These studies provide evidence that L-137 postbiotics play an important role in enhancing innate immunity by activating key immune cells and promoting a balanced immune response, thereby offering potential benefits for managing infections, allergies, and inflammatory conditions.

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