The study, led by teams at University Medicine Greifswald in Germany and Utrecht University in the Netherlands, exploited the TIMES cohort, an acronym for Tracking Individuals Monthly for Evaluating Stability. Participants, 32 women and 19 men with a mean age of about 34 years, donated blood once a month for twelve months between June 2017 and May 2018. This design is unusual in plasma proteomics, where most biomarker studies still rely on cross-sectional snapshots of a single time point per subject. By sampling repeatedly, the researchers could separate the variation that occurs within a person over time from the variation that exists between people, a distinction that is fundamental to interpreting any clinical measurement.

What makes the study particularly persuasive is its dual-laboratory architecture. The Greifswald site and the Utrecht site processed and analyzed the same samples using deliberately different workflows. One laboratory used a bead-based SP3 digestion protocol, the other a conventional liquid-phase digest. One measured peptides on a timsTOF Pro2 mass spectrometer, the other on the newer timsTOF HT, which features a fourth-generation trapped ion mobility analyzer with fivefold greater ion charge capacity. Even the software pipelines diverged: Greifswald searched raw data with Spectronaut against a large database of more than 42,000 human protein entries, while Utrecht used DIA-NN with a compact plasma-specific database of just 2,445 entries built from the Human Protein Atlas. Quantification strategies differed too, with Greifswald favoring intensity-based absolute quantification and Utrecht using MaxLFQ normalization.

Despite this deliberate methodological divergence, the two datasets agreed remarkably well. After filtering out contaminants and the hypervariable regions of immunoglobulins, Greifswald quantified 274 proteins and Utrecht 188, with 163 proteins overlapping. Comparing the two laboratories sample by sample, the mean Spearman correlation coefficient across all samples was 0.908 and the mean Pearson correlation was 0.824, indicating strong agreement in both the ranking of proteins and their absolute abundances. To make the numbers clinically meaningful, both sites converted relative intensities into absolute concentrations using a panel of 37 housekeeping plasma proteins with well-established reference values. The resulting estimates landed squarely within known clinical ranges, a benchmark that mass spectrometry workflows have historically struggled to meet.

With the analytical foundation secured, the team turned to the central biological question: how stable is a person’s plasma proteome over a year, and how different are people from one another? The answer came vividly from an unsupervised dimensionality reduction technique called UMAP, which projects high-dimensional protein data into two dimensions while preserving neighborhood structure. When all monthly samples from all donors were projected, each person’s twelve samples clustered tightly together, while the clusters of different donors sat far apart. In other words, your plasma proteome in January looks far more like your own proteome in December than like anyone else’s at any time of year.

To quantify this, the researchers built a machine learning classifier, a support vector machine with a radial basis kernel, and challenged it to identify which donor a blinded sample came from. Across 1,000 iterations, the model achieved a median classification accuracy of 98 percent. The proteome, in effect, carries a personal signature as distinctive as a fingerprint. Notably, statistical adjustment for age, sex and body mass index did not significantly reduce the inter-donor variability, suggesting that these common demographic confounders do not drive the observed differences in this cohort. The clustering was so robust that it even exposed a suspected sample mix-up: the December sample labeled as donor 27 sat squarely within donor 4’s cluster, prompting the team to exclude it as a probable aliquoting or labeling error.

The most consequential finding concerns the immunoglobulins, the antibody family that constitutes roughly 20 percent of total plasma protein mass. Because antibodies are extraordinarily polymorphic, with variable regions numbering in the millions of possible sequences, most plasma proteomics studies either physically deplete them or quietly ignore them in data analysis. This study did the opposite, retaining and quantifying them using peptides unique to the constant regions of each antibody class and subclass. The measurements showed that immunoglobulins vary enormously between donors but barely at all within a donor over twelve months. Total IgG averaged 9.75 grams per liter across the cohort with a standard deviation of 2.64 grams per liter, a 27 percent coefficient of variation, while the average intra-donor fluctuation was only about 1.11 grams per liter. The same pattern held for IgG subclasses IgG1 through IgG4, as well as IgM, IgA1, IgA2 and IgD, and it was mirrored by CD5L, a protein known to travel in complex with IgM.

The mass spectrometry-derived subclass distribution also matched the literature closely. IgG1 averaged 6.12 milligrams per liter of blood plasma, representing about 62.8 percent of total IgG, compared with a literature value of roughly 63.6 percent. IgG2 came in at 19.1 percent versus an expected 24.5 percent, IgG3 at 9.3 percent versus 5.7 percent, and IgG4 at 8.7 percent versus 6.3 percent. These numbers matter because they demonstrate that untargeted mass spectrometry can now deliver antibody measurements of clinical grade without the targeted immunoassays traditionally required. They also align with recent work showing that the dominant antibody clones in plasma are produced by long-lived plasma cells, which would explain why circulating immunoglobulin levels remain so stable over months.

Not everything in plasma stood still. C-reactive protein, the classic inflammation marker, behaved in a completely different manner. Most donors kept CRP concentrations low throughout the year, but a few individuals showed dramatic spikes, with one donor ranging from a basal 0.16 nanomolar to a peak of 721 nanomolar, a roughly 4,500-fold swing. Others, including six donors, maintained persistently elevated basal CRP of around 50 nanomolar across all twelve months, hinting at low-grade chronic inflammation. The episodic peaks were mirrored by sister inflammation markers SAA1, SAA2, S100A8 and S100A9, strengthening the interpretation that they reflect acute inflammatory episodes such as minor infections. The contrast between rock-steady antibodies and volatile CRP illustrates a key principle for biomarker research: some proteins define who you are, while others report what is happening to you right now.

The study also delivered an unplanned clinical vignette. One donor, identified as donor 26, showed immunoglobulin levels four to ten times below the cohort average for IgG1, IgG2, IgG3, IgA1 and IgM, all falling below the 2.5th percentile, combined with high body mass index and chronically elevated CRP. This pattern is suggestive of common variable immunodeficiency, the most prevalent primary immunodeficiency in humans, although the donor reported no increased susceptibility to infections. The researchers emphasize that this chance observation, surfaced purely through longitudinal proteomic screening, illustrates the diagnostic potential of the approach. More broadly, the work argues that biomarker discovery needs longitudinal designs, donor-specific baselines and cross-laboratory validation, and that a universal plasma reference material or isotopically labeled internal standards should accompany multi-center studies. If a single blood draw can be read against a person’s own stable proteomic baseline rather than a population average, the sensitivity of future diagnostics could improve substantially.

Subject of Research: Longitudinal mass spectrometry analysis of inter-donor variability in the human plasma proteome, focusing on immunoglobulin subclass stability

Article Title: Immunoglobulin sub-class levels define inter-donor plasma variability: a longitudinal dual-lab study

Article References: Michalik, S., Kalaidopoulou Nteak, S., Drouin, N., Gesell Salazar, M., Hammer, E., Dhople, V. M., Holtfreter, S., Weiss, S., van den Toorn, H. W. P., Bröker, B. M., Domańska, G., Völker, U., & Heck, A. J. R. (2026). Immunoglobulin sub-class levels define inter-donor plasma variability: a longitudinal dual-lab study. Molecular Systems Biology, 22(8), 1312-1332. https://doi.org/10.1038/s44320-026-00218-5

Image Credits: AI Generated

DOI: 10.1038/s44320-026-00218-5

Keywords: plasma proteomics, immunoglobulins, mass spectrometry, longitudinal study, biomarkers, C-reactive protein, IgG subclasses, inter-donor variability, machine learning, clinical diagnostics, TIMES cohort, proteome stability

Strongyloides stercoralis is a soil-transmitted helminth that infects an estimated 300 to 600 million people worldwide, yet it remains notoriously difficult to diagnose because the parasite persists at low levels in the intestine and sheds larvae intermittently. What makes the infection clinically dangerous is its unique ability to complete its life cycle entirely within the human host through autoinfection, allowing the worm to survive for decades. In individuals whose immunity becomes suppressed, for example by corticosteroid therapy or other conditions, the parasite can multiply uncontrollably and cause hyperinfection syndrome, a frequently fatal complication. Understanding the immune landscape of chronic infection is therefore not merely an academic exercise; it is central to identifying who is at risk and how the disease can be detected earlier.

The research team enrolled 82 individuals with confirmed S. stercoralis infection and 48 uninfected controls living in the same endemic region of Khuzestan province, a design that allowed them to distinguish infection-specific immune changes from background environmental exposures common to both groups. All infected participants presented with eosinophilia, an elevated count of eosinophils, the white blood cells classically associated with defense against parasitic worms. To probe the immune response, the investigators developed in-house enzyme-linked immunosorbent assays to measure antibodies directed against Strongyloides antigens, together with bead-based multiplex assays capable of quantifying a broad panel of cytokines and chemokines in serum.

The antibody results were striking in their subclass specificity. Infected individuals showed significantly elevated Strongyloides-specific immunoglobulin G responses compared with endemic healthy controls, but this elevation was not uniform across all IgG classes. Instead, IgG4 and IgG1 emerged as the dominant subclasses, while IgG2 responses were minimal. This pattern is immunologically meaningful: IgG4 is the subclass most consistently induced by chronic helminth exposure and is often interpreted as a marker of prolonged, repeated antigenic stimulation under a regulatory immune environment. The prominence of IgG1 alongside it suggests a robust, active antibody response to the parasite rather than a purely dampened one, painting a picture of coexisting activation and regulation that is characteristic of long-term worm carriage.

The cytokine data reinforced this type 2 orientation. Infected participants displayed significantly increased serum concentrations of interleukin-4, interleukin-5, interleukin-13, and interleukin-9, the canonical cytokines produced by type 2 helper T cells and, in the case of IL-9, by the increasingly recognized type 9 lineage. IL-4 drives class switching toward IgG4 and IgE, IL-5 recruits and activates eosinophils, and IL-13 promotes mucus production and tissue remodeling at mucosal barriers, all mechanisms directly relevant to expelling intestinal worms. The elevation of IL-9 adds an interesting dimension, as this cytokine has been implicated in mast cell responses and barrier immunity, processes thought to contribute to controlling helminth establishment in the gut.

Perhaps the most unexpected finding concerned the chemokine CXCL9, an interferon-inducible chemokine typically associated with type 1 inflammatory responses and the recruitment of T cells and natural killer cells. The researchers recorded a striking increase in CXCL9 among infected subjects, standing in apparent contrast to the dominant type 2 profile. Meanwhile, the majority of Th1- and Th17-associated cytokines, along with several pro-inflammatory chemokines, were either reduced during infection or increased after treatment and parasite clearance. This suggests that S. stercoralis actively suppresses inflammatory pathways while leaving, or even provoking, a specific interferon-driven chemokine signal, a combination that may reflect the parasite’s strategy of securing long-term survival while the host retains enough immune pressure to keep worm numbers in check.

A longitudinal component of the study strengthened the causal interpretation of these immune signatures. Eighteen patients were reassessed at least six months after receiving albendazole, one of the standard anthelmintic drugs used against strongyloidiasis. Following treatment and presumed parasite clearance, the researchers documented significant reductions in eosinophil counts, parasite-specific IgG1, IgG2, and IgG4 levels, and serum concentrations of both IL-9 and IL-10, the latter being an immunoregulatory cytokine often elevated during chronic helminth infection. In contrast, systemic IL-4 concentrations increased after therapy, an intriguing reversal that the authors note alongside the broader normalization of the infection-associated immune profile. The parallel decline of antibodies, type 2 cytokines, and regulatory signals after cure indicates that these markers track active infection rather than permanent immune reprogramming.

The clinical implications of this work are considerable. Serological diagnosis of strongyloidiasis already relies heavily on detecting parasite-specific antibodies, and the demonstration that IgG4 and IgG1 dominate the response supports the use of subclass-specific assays to improve sensitivity and specificity, particularly in endemic regions where cross-reactivity with other helminths complicates interpretation. Moreover, the finding that antibody levels and type 2 and type 9 cytokines fall measurably after successful treatment raises the possibility of using these immune markers as indicators of cure, something parasitological methods alone have struggled to provide given the intermittent shedding of larvae. In an era of increasing immunosuppressive therapy worldwide, reliable tools to verify parasite elimination before immunosuppression could save lives.

The study also contributes to a broader scientific conversation about how helminths modulate human immunity. Chronic worm infections are widely studied for their immunoregulatory effects, which some researchers hope to harness for treating autoimmune and inflammatory diseases. By documenting, in a well-characterized human cohort, the coordinated suppression of Th1 and Th17 pathways alongside a preserved interferon-inducible chemokine response, the Iranian-German team provides a nuanced dataset that moves beyond the simple dichotomy of type 1 versus type 2 immunity. It shows that natural infection produces a layered and partially contradictory immune landscape whose resolution after treatment can now be followed over time.

Limitations remain, as with any field study conducted in an endemic setting. The number of longitudinally followed patients was modest, and the six-month follow-up window, while sufficient to observe significant immune changes, leaves open questions about the long-term durability of antibody and cytokine normalization. The endemic controls, though carefully selected, cannot fully exclude prior exposure or unrecognized low-level infection. Nevertheless, the study stands as a substantial advance for a disease that has long been overshadowed by better-known tropical parasites. For the millions of people carrying S. stercoralis, many of them unaware of their infection, this work brings the prospect of sharper diagnostics, clearer markers of therapeutic success, and a deeper understanding of the delicate immune equilibrium that this remarkable parasite has evolved to maintain within its human host.

Subject of Research: Immune response profiling in Strongyloides stercoralis infection

Article Title: Systemic profiles of Strongyloides-specific IgG subclass, cytokine, and chemokine response in an eosinophilic Iranian population infected with Strongyloides stercoralis

Article References: Beiromvand, M., Ashiri, A., Rafiei, A., Heepmann, L., Hartmann, W., Linnemann, L., Tappe, D., Veit, A., & Breloer, M. (2026). Systemic profiles of Strongyloides-specific IgG subclass, cytokine, and chemokine response in an eosinophilic Iranian population infected with Strongyloides stercoralis. Parasites & Vectors. https://doi.org/10.1186/s13071-026-07683-9

Image Credits: AI Generated

DOI: 10.1186/s13071-026-07683-9

Keywords: Strongyloides stercoralis, strongyloidiasis, IgG subclasses, cytokines, chemokines, eosinophils, type 2 immunity, albendazole, immunomodulation, Iran, neglected tropical disease, parasitic infection