Four weeks of supplementation with Morinaga’s heat-killed Lacticaseibacillus paracasei MCC1849 was found to activate plasmacytoid dendritic cells (pDCs), which play a key role in the sensing of pathogens and adaptive immunity.
“This is the first report to show the beneficial effects of MCC1849 on immune cells in humans,” wrote scientists from Morinaga Milk Industry Co. and Medical Corporation Seishinkai in Nutrients. Morinaga funded the study.
“Because pDCs have a crucial role in maintaining healthy conditions, we consider that the activation of pDCs by the ingestion of MCC1849 contributes to appropriate immune responses and may have the potential to suppress subjective symptoms in healthy adults.”
The study used a heat-killed (dead) form of L. paracasei MCC1849, making this a postbiotic, defined by the International Scientific Association of Probiotics and Prebiotics (ISAPP) as a “preparation of inanimate microorganisms and/or their components that confers a health benefit on the host” (Nat Rev Gastroenterol Hepatol).
The Japan-based scientists recruited 100 healthy adults with an average age of 44 to participate in their randomized, double-blind, placebo-controlled, parallel-group study. The participants were randomly assigned to receive either 50 billion cells of MCC1849 or placebo for four weeks.
Results showed that ingestion of the postbiotic increased pDC activity in the blood. MCC1849 was also associated with maintaining the transcription of both type I and type II interferons (IFNs) stimulated by the TLR9 ligand. Dendritic cells express high levels of TLR9 (Toll-like receptor) and produce these IFNs when they sense a virus.
“Type I IFNs are also important for host defense because they contribute to signaling the infection and facilitating the communication among immune cells,” the authors explained. “Type I IFNs activate immune cells such as natural killer (NK) cells, B cells and T cells.
“It has been reported that 90% of URTIs [upper respiratory tract infections] are caused by viral infections. Therefore, pDCs, including their production of type I IFNs, seemed to be particularly important to prevent infection and relieve the symptoms of URTIs.”
Importantly, no adverse side effects were reported during the trial.
“These findings reveal one possible mechanism of how MCC1849 suppresses subjective symptoms,” the researchers concluded.
2024, 16(2), 216; doi: 10.3390/nu16020216
“Effects of Heat-Killed Lacticaseibacillus paracasei MCC1849 on Immune Parameters in Healthy Adults—A Randomized, Double-Blind, Placebo-Controlled, Parallel-Group Study”
Authors: K. Kato et al.