A substance the body makes from vitamin A can make the immune system less effective at fighting cancer, a new study reveals.

Vitamin A itself is an essential nutrient, but one of its byproducts can accidentally “turn off” parts of the immune response against cancer, according to new research published in Nature Immunology.

Blocking that byproduct’s effects can restore immune activity and may improve cancer immunotherapy, the findings suggest.

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Researchers at the Princeton University Branch of the Ludwig Institute for Cancer Research made this discovery by growing dendritic cells — key immune cells that activate the body’s defenses — in the lab. 

As these cells developed, the scientists noticed that they naturally turned on an enzyme that makes retinoic acid, a molecule that comes from vitamin A.

Retinoic acid can weaken dendritic cells’ ability to stimulate immune responses. This reduces the effectiveness of dendritic cell vaccines, an immunotherapy that trains the immune system to attack cancer, according to the study.

The researchers also found that when dendritic cells made a lot of the retinoic acid, they were less able to send strong danger signals to the immune system.

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When they removed the retinoic acid, the dendritic cells became stronger and better at activating T cells, which are the immune system’s cancer-killing cells.

A second study, published in iScience by collaborators from the same research group, looked at how to develop drugs to block this process.

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Using computer modeling and large drug screens, the team designed and identified small molecules that blocked the enzymes that produce retinoic acid. 

This led to the creation of a promising inhibitor that shuts down retinoic acid production in a controlled way — the same tool used in the first study’s experiments, the researchers noted.

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“Taken together, our findings reveal the broad influence retinoic acid has in attenuating vitally important immune responses to cancer,” lead researcher Yibin Kang said in a press release.

“In exploring this phenomenon, we also solved a long-standing challenge in pharmacology by developing safe and selective inhibitors of retinoic acid signaling and established preclinical proof of concept for their use in cancer immunotherapy.”

Study limitations

As these findings are based on laboratory and animal models, they may not fully reflect how retinoic acid functions in humans.

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Also, the studies examined a specific vitamin A-derived molecule (retinoic acid) acting in immune cells, not dietary vitamin A intake or overall vitamin A status.

Vitamin A remains an essential nutrient for normal immune function, growth and vision, according to the National Institute of Health, and extensive human studies have found no evidence that vitamin A causes cancer.

The South Carolina measles outbreak has spread to Clemson University.

The state’s Department of Public Health informed Clemson staff of a “confirmed case of measles” in an individual associated with the university, according to an update from the school published Saturday.

“The individual has isolated, per DPH requirements, and DPH is conducting contact tracing with individuals who may have been exposed and outlining isolation and quarantine protocols,” the school stated.

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Individuals thought to be exposed to the virus will be contacted via email about quarantining.

Officials are reporting 558 cases of measles centered around Spartanburg County in the current outbreak.

Some cases are travel-related exposures or close contacts with known cases, according to the DPH.

Other cases have no identified source, suggesting that measles is circulating in the community and could spread further.

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“Over the last seven to nine days, we’ve had upwards of over 200 new cases. That’s doubled just in the last week,” said Dr. Johnathon Elkes, an emergency medicine physician at Prisma Health in Greenville, South Carolina, during a media briefing Friday.

“We feel like we’re really kind of staring over the edge, knowing that this is about to get a lot worse.”

Nearly 98% of main campus Clemson students have provided proof of immunity, according to the most recent data from Student Health Services.

“The health, safety and well-being of Clemson’s campus community remains our highest priority,” the school noted.

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Measles is highly contagious, according to the Centers for Disease Control and Prevention. If one person has it, up to nine out of 10 people will become infected if not protected.

“We feel like we’re really kind of staring over the edge, knowing that this is about to get a lot worse.”

A person infected with measles is contagious for four days before and after a rash begins. Isolation of an actively infectious case lasts until four full days have passed after the onset of the rash. 

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Dates of isolation are determined by DPH, according to the university press release.

Quarantine for measles is reserved for exposed individuals without documented immunity, and lasts for 21 days after the last exposure, per DPH guidelines.

If a person without documented immunity receives a dose of the MMR vaccine within 72 hours after the last exposure, that person does not have to quarantine.

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The university also claims to have previously provided guidance to students, faculty and staff regarding measles preparedness. 

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More information is available on the Student Health Services website and through the South Carolina Department of Public Health’s measles updates.

Physical decline does not wait for old age. 

A new study tracked the same people for nearly half a century, finding that measurable drops in fitness and strength begin at around age 35 and continue gradually through midlife.

The study is based on the Swedish “Physical Activity and Fitness” cohort, which began in 1971 with participants born in 1958. Researchers enrolled 427 people, a mix of men and women, and tested the same individuals repeatedly over a 47-year span, according to a press release.

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Models were used to estimate age- and sex-specific changes in the original cohort during the study period.

The follow-up examinations took place at several points across adulthood, allowing the Karolinska Institutet researchers to observe changes within individuals rather than relying on comparisons between different age groups, the release stated.

At each examination, participants underwent standardized physical testing conducted by trained professionals. Aerobic fitness was measured using tests that assessed peak oxygen uptake, a common indicator of cardiovascular capacity.

Muscle strength and muscular endurance were evaluated through controlled performance tests, including grip strength and repetitive movement tasks. Height, weight and other basic physical measures were also recorded, and participants provided information about their physical activity habits.

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By using the same tests over time, the researchers were able to track long-term trends in physical performance.

The results showed that physical performance peaks in early adulthood and begins to decline around the mid-30s.

This decline was observed across multiple measures, including aerobic fitness and muscle strength, and continued steadily into later adulthood, the researchers shared.

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While individuals who were physically active tended to retain higher overall fitness levels, activity did not completely prevent age-related decline. 

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Even so, the data showed that participants who increased their activity levels later in life improved their physical capacity by roughly 5% to 10%, demonstrating that the body remains responsive to exercise beyond peak years.

Study limitations

The study, which was published in the Journal of Cachexia, Sarcopenia and Muscle, consisted of individuals who were born in the same year and were living in Sweden. 

This may limit how the findings apply to other populations with different social, environmental or genetic backgrounds, the researchers acknowledged.

As with any long-term study, some participants dropped out over time, which could affect how well the sample reflects the original population. 

Also, physical performance was measured at specific intervals, so short-term fluctuations between testing periods were not captured.

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In addition, while physical activity was associated with better outcomes, the observational nature of the study means other factors such as diet, occupation or health conditions may also have influenced results, the researchers stated.

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The team plans to continue following the cohort as the participants grow older, with the goal of linking changes in physical capacity to health outcomes later in life.