The study was conducted by internists Muhammet Ateş and Barış Karagün of the Department of Internal Medicine at Adana City Training and Research Hospital in Adana, Türkiye. Working from the hospital’s anonymized records, the pair assembled a retrospective cohort of 220 adults admitted for treatment of an infected diabetic foot wound. For every patient, they recorded the admission serum concentration of 25-hydroxyvitamin D, the stable storage form of vitamin D that clinical laboratories use as the standard yardstick of vitamin status. Deficiency was defined, in line with conventional thresholds, as a level below 20 nanograms per milliliter. The prevalence result was arresting: 109 of the 220 patients, or 49.5 percent, were vitamin D deficient on the day of admission. In other words, roughly one in every two patients arriving with a diabetic foot infection was already running on empty reserves of a hormone-like nutrient that immune cells depend on.

Diabetic foot infection is among the most feared complications of diabetes, and its biology explains why. Chronically high blood sugar damages peripheral nerves, so patients lose the protective pain sensation that would normally alert them to a blister or small ulcer early. Meanwhile, diabetes narrows and stiffens the arteries of the leg, starving the wound of the oxygen and immune cells that healing requires. Hyperglycemia also handicaps the defenses directly: neutrophils, the frontline white blood cells that engulf bacteria, move, adhere and kill less efficiently when glucose runs high. The result can be an ulcer that progresses from a superficial sore to a deep, bone-invading infection. To standardize comparisons, the researchers graded every infection using the criteria of the International Working Group on the Diabetic Foot and the Infectious Diseases Society of America, which classify infections as mild, moderate or severe according to depth, extent and the presence of a systemic inflammatory response. In this cohort, 103 patients (46.8 percent) had mild infections, 66 (30.0 percent) moderate and 51 (23.2 percent) severe.

The first biomarker, vitamin D, is less a vitamin than a secosteroid hormone. The 25-hydroxyvitamin D measured in the study is produced in the liver and circulates for weeks as the body’s reservoir; the kidneys and, crucially, immune cells themselves convert it into the active hormone 1,25-dihydroxyvitamin D. Immune cells are not bystanders in this system. Macrophages, dendritic cells and lymphocytes carry vitamin D receptors, and when activated vitamin D binds to them, it switches on genes encoding antimicrobial peptides such as cathelicidin—natural antibiotics that disrupt bacterial membranes—while tempering the release of inflammatory cytokines. Deficiency is especially common in type 2 diabetes: excess adipose tissue sequesters the fat-soluble vitamin, chronic hyperglycemia interferes with its activation, and diabetic kidney impairment can blunt the final activation step. A level below 20 ng/mL, the threshold used here, is conventionally read as frank deficiency—a state in which the immune system may be operating without one of its chemical co-pilots.

The second biomarker family is even cheaper: four inflammation indices computed arithmetically from the standard complete blood count that virtually every admitted patient already receives. The neutrophil-to-lymphocyte ratio divides the absolute neutrophil count by the absolute lymphocyte count, capturing the classic signature of acute physiological stress—neutrophils surge into the circulation under cortisol, catecholamines and interleukin-6, while lymphocytes fall. The platelet-to-lymphocyte ratio adds platelets, which climb as part of the inflammatory response. The systemic immune-inflammation index multiplies platelet count by neutrophil count and divides by lymphocyte count, producing a composite gauge of the combined inflammatory armament. The systemic inflammation response index multiplies neutrophils by monocytes—the cells that sustain and orchestrate chronic inflammation—divided by lymphocytes. Because all four indices can be derived from numbers already printed on any admission blood panel, they cost nothing and can be calculated within minutes of arrival, turning routine laboratory output into an immediate readout of the body’s inflammatory temperature.

When the researchers split the cohort by vitamin D status, the deficient group looked sicker across the board. Body mass index averaged 32.1 versus 29.9 kg/m² in the replete group, and long-term glucose control, gauged by glycated hemoglobin (HbA1c), was substantially worse at 9.1 versus 8.3 percent, with both comparisons significant at p < 0.001. The inflammatory indices told the same story: median NLR was 5.7 (interquartile range 4.3–7.3) in deficient patients versus 3.6 (3.0–5.0) in those with adequate vitamin D, while the systemic immune-inflammation index registered 1774.0 (1282.0–2499.0) versus 1042.0 (812.5–1450.0). The most consequential difference was time: deficient patients spent a median of 14.0 days in hospital (interquartile range 12.0–17.0), compared with 10.0 days (8.0–12.0) for the replete. Severe infection was more than three and a half times as common in the deficient group, affecting 36.7 percent versus 9.9 percent. On every measure captured at the bedside, low vitamin D flagged a patient in deeper trouble.

Equally striking was the graded pattern across infection severity. Moving from mild to moderate to severe disease, mean 25-hydroxyvitamin D stepped down in lockstep, from 22.1 ± 4.8 ng/mL in mild cases to 17.1 ± 4.2 ng/mL in severe ones, while median NLR climbed from 3.3 (2.7–4.0) to 8.2 (6.9–9.1), both trends robust at p < 0.001. In epidemiology, such a dose-response gradient is one of the classic signals that an association may be more than statistical noise: the deeper the infection, the lower the vitamin and the hotter the inflammation. Alongside these group comparisons, the team ran correlation analyses, logistic regression, linear regression and receiver operating characteristic analyses, a statistical battery designed to test whether the raw associations would survive once other clinical variables entered the equation.

The decisive results came from the multivariable models. In adjusted logistic regression, two variables emerged as independently associated with severe infection: the admission NLR, with an adjusted odds ratio of 3.06 per unit increase (95 percent confidence interval 2.09–4.48, p < 0.001), and serum albumin, with an adjusted odds ratio of 0.10 per unit increase (95 percent confidence interval 0.01–0.76, p = 0.026). Albumin, the liver’s most abundant export protein, is a negative acute-phase reactant: its concentration falls as inflammation ramps up, as nutrition falters and as damaged vessels leak protein into tissue. A low albumin therefore works as a composite alarm for catabolism, malnutrition and systemic illness—precisely the terrain on which severe diabetic foot infections flourish. Notably, vitamin D deficiency itself dropped out as an independent predictor of severity once other variables were accounted for. For length of stay, however, deficiency held its ground: in adjusted linear regression, vitamin D deficiency carried a coefficient of 0.192 (95 percent confidence interval 0.112–0.273, p < 0.001) and NLR a coefficient of 0.052 (95 percent confidence interval 0.036–0.068, p < 0.001), meaning both remained associated with longer admissions after correction.

The authors are explicit that these are associations, not verdicts on causation. The study was retrospective and single-center, built on anonymized hospital records from one institution; the protocol was approved by the hospital’s ethics committee in March 2026, with informed consent waived under the anonymized design. Reverse causality is a live possibility: systemic infection and inflammation can themselves disturb vitamin D metabolism and suppress its circulating levels, so a low 25-hydroxyvitamin D reading may partly be a consequence of severe illness rather than a contributor to it. Deficiency could also simply be a proxy for the metabolic storm that surrounds diabetic foot disease—obesity, poor long-term glycemic control, malnutrition and reduced mobility all deplete vitamin D while independently worsening outcomes. Ateş and Karagün accordingly frame their results as hypothesis-generating. Their conclusion draws a careful line: elevated admission NLR and hypoalbuminemia may warrant closer assessment for severe infection, while low 25-hydroxyvitamin D should be interpreted as a marker of overall vulnerability rather than a target that correction alone is guaranteed to fix. No vitamin D supplementation was tested.

Even so, the practical signal is difficult to ignore. The two instruments that carried the strongest associations—a white-cell ratio and a vitamin level—are among the cheapest tests in existence, orderable in any emergency department in the world. If prospective studies replicate these findings, an admission checklist for diabetic foot patients could take shape: calculate the NLR, check the albumin, note the vitamin D. Patients with a high ratio and low protein might be routed toward closer monitoring, earlier imaging for deep involvement and more aggressive initial antimicrobial therapy, while deficient patients could simply be expected to stay longer and be planned for accordingly. The study also feeds a broader scientific current: the search for free, computable inflammation gauges that transform routine blood counts into risk stratification. With diabetes prevalence climbing worldwide and foot disease claiming a heavy share of diabetes-related hospital days, a zero-cost warning system read off numbers clinicians already possess is exactly the kind of simple idea with far reach. Whether restoring vitamin D can shorten those fourteen-day stays is a question only intervention trials can answer.

Immune cells are pivotal sentinels, constantly patrolling the body to detect and eliminate pathogens. Their ability to navigate tissues efficiently is crucial for timely immune responses. Intriguingly, this motility appears exquisitely sensitive to temperature changes, a fact that has been observed but not thoroughly dissected at the molecular scale. About a decade ago, Wieser’s initial experiments—conducted in cell culture environments—revealed that raising the ambient temperature from room temperature (20 °C) to near fever-level warmth (40 °C) resulted in a dramatic increase in immune cell motility. Cells cultured at lower temperatures exhibited markedly diminished movement, almost halting altogether, whereas warmer conditions propelled them into rapid motion. This observation hinted at a fundamental thermoregulatory mechanism waiting to be unraveled.

The enigmatic question was: what molecular processes enable immune cells to translate temperature shifts into altered behavior so promptly? Genetic regulatory pathways, typically requiring minutes to hours, could not explain the near-instantaneous acceleration observed. This discrepancy suggested that biophysical forces and rapid protein activity adjustments underlie the thermal responsiveness. Wieser, together with co-author Verena Ruprecht and their colleagues within the newly formed Quantitative Biology (QBIO) group, embraced an interdisciplinary approach combining cellular biology, biophysics, and high-resolution microscopy to probe these mechanisms with unprecedented precision.

A transformative phase of the research unfolded during Wieser’s tenure at the Institute of Photonic Sciences (ICFO) in Barcelona, where access to advanced imaging technologies enabled systematic examination of immune cell motility in both cultured cells and living models, including zebrafish and mice. Central to this investigation was the deployment of a custom-engineered thermo-microscope, designed to permit exact temperature manipulation at the single-cell level while simultaneously capturing dynamic cellular responses through fluorescence imaging. This innovative platform allowed the team to mimic physiological temperature gradients and observe immune cells’ mechanical adaptation in real time.

Their results were nothing short of remarkable. Among diverse human leukocyte populations—T cells, macrophages, dendritic cells, and neutrophils—the increase from 25 °C (commonly referred to as “cold”) through a physiological baseline of 37 °C, up to febrile temperatures of 41 °C elicited an exponential rise in migration velocity. Quantitatively, some cells exhibited up to a tenfold enhancement in speed. This rapid kinetic shift also translated to a greater number of immune cells infiltrating lymphatic vessels, a key step in mounting effective adaptive immune responses. The speed and immediacy of these changes effectively ruled out classical gene expression changes, pointing instead to an immediate molecular motor-based mechanism.

Enter Myosin II, a versatile motor protein well characterized for its roles in cellular contractility, locomotion, and cytokinesis. The team showed that Myosin II’s capacity to generate mechanical force is directly modulated by temperature oscillations, particularly when temperatures rise above the physiological norm of 37 °C. This temperature-dependent modulation hinges on Myosin II’s ATPase activity—its ability to convert chemical energy from ATP hydrolysis into mechanical work intensifies as thermal energy increases. This enhanced force production effectively propels immune cells faster through tissue matrices and facilitates quicker transendothelial migration.

Critically, this study highlights Myosin II’s function not merely in baseline cell motility but as a cellular thermostat that tunes immune responsiveness according to thermal cues. This thermosensitivity has profound physiological implications: fever, often perceived solely as a symptom, emerges here as an evolutionarily conserved mechanism that accelerates immune surveillance and response, providing a tangible molecular basis for the protective role of elevated body temperature during infection.

Beyond human cells, the researchers found indications that this thermo-adaptive mechanism is conserved across warm- and cold-blooded species alike, underscoring the fundamental nature of this regulatory pathway. This cross-species conservation opens intriguing avenues for broader ecological and evolutionary studies on immune system adaptability under varying environmental temperatures.

Technically, the research leveraged state-of-the-art fluorescence microscopy and quantitative biophysics to dissect the interplay between intracellular force generation and motility. The high temporal resolution of the thermo-microscope unveiled that leukocyte mechanical dynamics respond almost instantaneously—within seconds—to temperature shifts. Such immediacy delineates Myosin II-driven motility as a unique rapid-response mechanism distinct from slower biochemical signaling cascades or transcriptional regulation, underscoring the elegant efficiency of cellular mechanotransduction.

This newly elucidated role of Myosin II in temperature-dependent immune cell motility not only deepens our comprehension of immune physiology but also prompts a reevaluation of fever’s clinical significance. It suggests that therapeutic strategies manipulating Myosin II activity or mimicking thermal modulation might augment immune efficacy, particularly in immunocompromised or elderly patients whose febrile responses may be blunted.

Looking forward, Wieser and his colleagues anticipate that their findings will stimulate a wealth of novel research paths. Key questions include deciphering how Myosin II’s mechanical properties are biochemically tuned at different temperatures, how this motor protein integrates with other cytoskeletal components to modulate cell morphology and signaling, and whether similar thermo-adaptive mechanisms operate in other immune cell functions such as phagocytosis or cytokine secretion.

In sum, this pioneering work casts new light on the intricate relationship between temperature and immunity, establishing Myosin II as a central molecular player in the thermo-adaptability of immune responses. By bridging cellular biophysics with immunology, Wieser’s study paves the way for innovative explorations into how the body harnesses physical forces to safeguard health, particularly under the dynamic thermal conditions encountered during infection and inflammation.

Subject of Research: Cells

Article Title: Myosin II regulates cellular thermo-adaptability and the efficiency of immune responses

News Publication Date: 4-Nov-2025

Web References: DOI: 10.1016/j.devcel.2025.10.006

Image Credits: Stefan Wieser

Keywords: Immune cell motility, Myosin II, temperature sensitivity, febrile response, cellular biophysics, thermo-adaptability, immune response acceleration, fluorescence microscopy, ATPase activity, leukocyte migration