Arginine is an amino acid obtained from protein-rich foods (meat, fish, dairy, nuts, legumes) and produced endogenously. Beyond protein synthesis, arginine supports multiple physiological processes including blood flow, wound healing, and immune function.
The researchers analyzed existing amino acid data from cancer tissues and from lungs of mice infected with influenza or SARS-CoV-2. Arginine emerged as one of the most consistently depleted amino acids across these conditions. The team noted that cancer and some viral infections can activate immune cells that express arginase, an enzyme that breaks down arginine and can reduce its availability in tissues.
To probe consequences for immune recognition, the investigators restricted arginine in human and mouse colorectal cancer cells and tested additional human cancer cell lines from melanoma, breast, stomach, and pancreatic cancers. They measured levels of major histocompatibility complex class I (MHC-I), a protein complex that displays antigen-derived peptides on cell surfaces and enables cytotoxic CD8 T cells to detect infected or abnormal cells.
Under arginine restriction, cancer cells displayed lower MHC-I levels and presented fewer antigens. Functionally, this reduced antigen display led to decreased recognition and killing by CD8 T cells. When arginine was restored after 24 hours of restriction, MHC-I expression recovered within hours. The authors linked low arginine to ribosome stalling during MHC-I protein production, providing a mechanistic explanation for the reduced antigen presentation.
These findings indicate that tissue arginine availability can modulate antigen presentation machinery and subsequent immune detection in both tumor and infected cells.
The team tested dietary arginine manipulations in mouse models. In colorectal cancer experiments, mice receiving additional dietary arginine developed fewer and smaller tumors, while mice on arginine-restricted diets developed more tumors. These in vivo tumor findings aligned with the in vitro observation that lower arginine reduces antigen display and impairs CD8 T cell–mediated killing.
Separate infection experiments evaluated the effects of arginine supplementation on influenza and a mouse-adapted form of SARS-CoV-2. In mice with influenza, arginine supplementation reduced weight loss and mortality; benefits were observed even when supplementation began one day after infection. In mice infected with the mouse-adapted SARS-CoV-2, supplementation reduced weight loss, lowered viral levels, and decreased lung damage.
Mechanistic data from cell and tissue studies supported the interpretation that increased arginine restored MHC-I production and antigen display, thereby improving immune recognition and clearance in these models.
The study lead, Sohail Tavazoie, MD, PhD, stated that the amount of arginine used in supplementation corresponds to about 10 grams per day in humans. The authors note interest in testing arginine supplementation in high-risk people with influenza and potentially other settings, but they emphasize the need for human trials to determine safety and efficacy.
The National Institutes of Health reports that doses in the range of 9 to 30 grams may cause gastrointestinal discomfort and modest reductions in blood pressure, highlighting the importance of clinical evaluation of dosing strategies before clinical use.
External experts not involved in the study described the findings as intriguing but emphasized limitations. Anton Bilchik, MD, PhD, a surgical oncologist, noted arginine is inexpensive and widely available and that many healthy people may tolerate about 10 g daily; he cautioned that this dose may pose risks for people with kidney or liver disease and advised consulting a healthcare professional before use.
Jagdish Khubchandani, PhD, MPH, highlighted that the experiments were conducted in highly controlled animal and cell models and focused on specific antiviral and antitumor conditions. He stated that without human trials the findings have limited clinical value and that researchers still need to determine who might benefit and under what circumstances.
Both experts recommended against self-prescribing high-dose arginine with the expectation of boosting immunity or improving cancer outcomes until definitive human data are available. They advised that people with cardiovascular, kidney, or liver disease and pregnant people should not take the amounts referenced without medical guidance.
In summary, the study presents preclinical evidence that tissue arginine availability affects MHC-I production, antigen display, and immune recognition, and that dietary supplementation improved tumor and viral outcomes in mouse models. Human clinical trials are required to confirm these effects, establish safe and effective doses, and identify patient populations that might benefit.