New Confirmation That LC-Plasma Suppresses The Decreased Activity Of pDC Immune Cells pDC Under High Temperature Conditions

Research Results (Summary)

Human-derived pDCs were cultured at normal temperature (37°C) or high temperature (38.5°C) and IFN-α*2 was measured 48 hours after adding only H1N1*3 or both LC-Plasma and H1N1 production was measured. Under high temperature conditions, the function of pDCs decreased, and the addition of LC-Plasma tended to counter this decrease in activity.

Key Findings

These results suggest that LC-Plasma is an effective means of maintaining pDC activity, which declines under high temperature conditions.

*2 Interferon α, an antiviral substance
*3 Inactivated influenza virus

Explanation by Dr. Yasuhiro Nishizaki, MD

On June 1, 2025, Japan amended the Labor Safety and Health Act, making heatstroke prevention measures mandatory in the workplace with penalties for non-compliance. Heatstroke is a life-threatening condition caused by dehydration and a rise in core body temperature. In Japan, last year, from May to September, a record 97,578 people were transported to emergency rooms, with 120 deaths and 2,178 requiring hospitalization for three weeks or more. With this year's heatwave expected to be as severe as last year's, robust preventive measures are essential.

In this study, we first cultured plasmacytoid dendritic cells (pDCs), which act as the immune system's leader, at temperatures matching the human core body temperature of 37°C and 38.5°C. We then added the antigen of influenza A H1N1 to the culture medium. The H1N1 antigen is a structural component of the influenza A virus, present in the 1918 Spanish flu, the 1977 Soviet flu, and the novel influenza that caused a global pandemic in 2009. While the antigen alone lacks the ability to replicate and thus cannot cause infection, it does elicit immune responses similar to those observed during infection. After 48 hours of mixed culture, at 37℃ , the secreted interferon α (IFN-α), which inhibits viral replication, more effectively than pDCs. However, at 38.5°C, this secretion was suppressed. This indicates that under 38.5°C conditions, pDCs cannot effectively secrete interferon and thus cannot defend against viral infection. However, when Kirin's LC-Plasma (Lactobacillus lactis) was added, interferon-alpha secretion increased approximately 25 times compared to when cultured at 37°C, proving its powerful protective effect.

The cause of death from heat stroke is often multiple organ failure, and it is medically known that, in addition to avoiding dehydration, it is important to take care of the immune system to prevent heat stroke.

Analysis using a heatstroke model has revealed that endotoxins, toxins found in the intestines, spread due to immune system abnormalities caused by high body temperature and dehydration, leading to a state called "endotoxemia," which can result in severe complications.
When temperatures are high, humans sweat to lower surface body temperature, which in turn lowers core body temperature. However, the "cytokine storm" triggered by endotoxemia causes fever from within the body, directly raising core body temperature. Ultimately, endotoxemia induces systemic inflammatory responses, leading to multiple organ failure.
Regular immune care and adequate hydration are key to preventing heatstroke.

Doctor of Medicine: Yasuhiro Nishizaki

Graduated from Tokai University School of Medicine in 1986. After completing his graduate studies at Keio University School of Medicine and serving as a research fellow at UCLA, he is currently a professor and chair of the Department of Health Management in the Division of General Internal Medicine at Tokai University School of Medicine, director of the Life Care Center at Tokai University Graduate School of Medicine, president of the Japan Society of Health Evaluation and Promotion, president of the International Health Evaluation and Promotion Association, and president of the National Center for Geriatrics and Gerontology. His areas of expertise include preventive medicine, anti-aging medicine, and gastroenterology. He has also been involved in joint research on LC-Plasma.