HomeScience and ResearchScientific ResearchDoes This Mean a High-Fat Diet Could Protect You Against Pneumonia?

Does This Mean a High-Fat Diet Could Protect You Against Pneumonia?

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Could eating fatty foods really protect you from lung inflammation caused by a bacterial or viral infection?

Is there a link between the consumption of fatty foods and a reduced risk of developing pneumonia?

Immunologists and clinicians have recently turned their attention to a fascinating population of white blood cells that possess remarkable characteristics. Unlike the conventional T cells that circulate in the bloodstream, these specialized cells, known as mucosal-associated invariant T (MAIT) cells, predominantly reside in tissues where they play a crucial role in safeguarding against a wide spectrum of diseases.

In humans, MAIT cells are remarkably abundant. Although they constitute a mere 2 percent of lymphocytes in the blood, they make up an impressive 10 to 40 percent of lymphocytes in the liver and are commonly found in tissues such as the lungs. However, despite their prevalence, much remains unknown about the biology and clinical functions of MAIT cells.

A recent study published in Nature Cell Biology delves into the comprehensive exploration of MAIT cells in the lungs of mice, shedding light on their location, function, gene expression, and metabolism. Researchers at the La Jolla Institute for Immunology (LJI) conducted this groundbreaking investigation.

Unconventional White Blood Cells with Unique Immune Role Discovered

“Metabolism is the way your cells use fuel molecules to do their work,” explains first author Thomas Riffelmacher. “There’s been a recent revolution in the field in which studies are starting to link the function of T cells to their metabolic programming, but this had not yet been explored in MAIT cells.” 

In order to lead the way in this area of research, Riffelmacher collaborated with Mitchell Kronenberg, Ph.D., a renowned expert on innate-like T cells known for their swift responses, who serves as a Professor and Chief Scientific Officer at LJI. Together, they conducted groundbreaking research to delve into the characteristics of MAIT cells and their role in combating pathogens.

Through their efforts, they uncovered two distinct categories, or “flavors,” of MAIT cells: an antiviral subtype that relies on sugar as its energy source, and an antibacterial subtype that thrives on fat. These findings hold significant potential to inspire innovative approaches in the development of vaccines and cell therapies. By manipulating the balance between these two subgroups, it may be possible to enhance individuals’ ability to combat specific pathogens, leading to more effective treatment strategies.

A Tale of Two Cell Types: Unveiling the Remarkable Features of MAIT Cells

MAIT cells demonstrate amplified memory-like reactions subsequent to certain infections, characterized by increased cellular quantities and potent defensive responses that fortify the host’s immune system long after the eradication of the pathogen. Riffelmacher’s original objective was to investigate the molecular alterations that underlie this crucial memory capacity in MAIT cells.

To delve into the subject, Riffelmacher administered a live bacterial vaccine strain to a mouse model, which led to a striking 100-fold expansion of MAIT cells in the animals’ lungs within a matter of days. However, an unexpected observation emerged as he noticed the emergence of two distinct subsets within this expanded MAIT cell population. Through a series of comprehensive experiments aimed at characterizing these two cell lineages, several distinct properties came to light.

The first subset, primarily localized along blood vessels in the lungs, consisted of MAIT cells that exhibited a type 1 immune response, characterized by the secretion of a cytokine called interferon-gamma (IFN-ɣ). These particular lymphocytes, termed MAIT1 cells, were specifically equipped to combat intracellular microbes, particularly viruses like influenza.

The second subset of MAIT cells, predominantly present in lung tissue, showcased a type 17 immune response, marked by the secretion of a different cytokine known as interleukin-17 (IL-17). These cells, referred to as MAIT17s, were specialized in countering extracellular microbes, specifically bacteria that contribute to pneumonia.

To demonstrate their distinct protective properties, the researchers purified the MAIT1 and MAIT17 cells and transferred them into new mice. Both populations remarkably enhanced the animals’ immunity compared to untreated mice. However, MAIT1 cells provided superior defense against the influenza virus, while MAIT17 cells demonstrated efficacy in protecting against Streptococcus pneumoniae, the most common cause of pneumonia.

Beyond their functional disparities, the metabolic programs of these two cell types proved to be highly divergent—an intriguing finding that captured Riffelmacher’s attention. Each cell type appeared to derive its energy from a distinct source.

“I remember seeing this first batch of data and thinking, ‘Wow, this is a huge difference—we need to look into this,’” adds Riffelmacher.

MAIT1 cells remained in a dormant, low-energy state until activated, relying on sugar (glycolysis) as their primary fuel source. In contrast, MAIT17 cells exhibited high activity levels and relied on a continuous intake of fatty acids to generate sufficient energy through their mitochondria. Manipulating the metabolism of white blood cells in the study, the researchers were able to favor glycolysis, resulting in elevated numbers of MAIT1 cells, thereby confirming the influence of metabolism on the MAIT cell response.

Could Consuming Fatty Foods Provide Protection Against Pneumonia?

According to Kronenberg, the impact of diet on metabolite distribution within the body is acknowledged, but it’s important to note that cellular and organismal metabolism function differently. Therefore, there is currently no conclusive evidence that altering dietary patterns would directly influence the functioning of MAIT cells.

However, researchers have successfully manipulated the levels of metabolites in animal models using pharmacological methods. This manipulation resulted in a shift in the animals’ MAIT cell response, potentially enhancing their ability to combat viral infections or bacterial pathogens.

In order to translate these findings into clinical applications for humans, the researchers propose several strategies. One approach involves developing vaccines that specifically activate either MAIT1 or MAIT17 cells, thereby boosting a targeted immune response. Alternatively, transplanting a specific subtype of MAIT cells into patients could also be explored to enhance a particular immune response. Notably, MAIT cells and their primary signaling protein exhibit a high degree of conservation across various individuals and species. As a result, the risk of triggering a graft-versus-host response, which is commonly associated with other types of white blood cells, is significantly reduced when working with MAIT cells.

“Our hope is that in the future, we’ll have tools to selectively enhance MAIT1s or MAIT17s so that patients can have their immune systems tuned against different pathogens as necessary,” points out Kronenberg. 

Source: 10.1038/s41556-023-01152-6

Image Credit: Getty

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