Welcome to KodaKoda's Weekly Immunology News. I am so glad you are here for another episode packed with fascinating discoveries from the world of immunology and microbiology. We have got a lot to cover this week, from the immune system sculpting brain circuits to bacteria sensing viral attacks, to new insights about cancer immunity and allergic responses. Let us dive right in.
We are starting with a story that brings together neuroscience and immunology in a way that might surprise you. Published on July 9th, 2026 in the journal Science, a paper titled C1q and immunoglobulins mediate activity-dependent synapse loss in the adult brain comes from Gerard Crowley at the UK Dementia Research Institute, Institute of Neurology, University College London. And there is an accompanying perspective piece by Lauritz Miarka at the Institute of Neuropathology, University of Freiburg, that summarizes it beautifully by saying that immune cells target hyperactive neurons to eliminate synaptic connections.
So what is actually going on here? The brain is full of connections between neurons called synapses, and it turns out the immune system plays an active role in deciding which synapses get to stay and which ones get pruned away. The key player in this story is a protein called complement component 1q, or C1q for short. C1q is the very first step in what is called the classical complement cascade, which is a chain reaction of immune proteins that can tag things for destruction. We have known for a while that C1q helps eliminate synapses during brain development, but what has been unclear is what tells C1q to land on a particular synapse in the first place.
In this study, the researchers used a technique called in vivo chemogenetics, which is essentially a way to remotely switch neurons on or off in a living animal using specially designed chemical tools. They showed that when neurons become hyperactive, that activity actually triggers C1q to deposit on those synapses, leading to their elimination specifically in a brain region called the adult hippocampus. That is really striking because it means the immune system is actively monitoring neuronal activity and responding to it.
Then they took this further into an Alzheimer's disease mouse model. When they suppressed hyperactivity along a pathway called the perforant pathway, they saw reduced amounts of amyloid beta, the sticky protein that accumulates in Alzheimer's disease, and also reduced C1q deposition, and this partially rescued the synapse loss. So the hyperactive neurons seem to be driving their own destruction through this immune mechanism.
But perhaps the most unexpected finding is about who is giving the orders to C1q. Using spatial transcriptomics, live cell tracking, and super-resolution microscopy, the team found that antibody-secreting B lineage cells are present in the adult hippocampus and are associated with this activity-dependent synapse pruning under normal physiological conditions. That means immunoglobulins, which are antibodies produced by B cells, appear to be involved in marking synapses for removal by C1q. This is quite a revelation because it implicates the adaptive immune system, specifically the antibody branch, in what we thought was a more innate process of synaptic maintenance in the brain.
Moving on to another Science paper from July 9th, this one titled The CARM1 epigenetic enzyme inhibits cross-presenting dendritic cell function in cancer immunity, from Xixi Zhang at the Department of Cancer Immunology and Virology at Dana-Farber Cancer Institute in Boston. This paper is all about how cancer manages to slip past our immune defenses, and more importantly, how we might stop that from happening.
The cancer-immunity cycle depends critically on a special type of immune cell called cross-presenting type I conventional dendritic cells, or cDC1s. These cells have a unique superpower: they can pick up cancer antigens and present them to killer T cells in a way that activates those T cells to attack the tumor. The problem is that in many tumors, this process is suppressed, and we do not have great tools to fix it.
The researchers found that an enzyme called CARM1, which stands for coactivator-associated arginine methyltransferase 1, acts as a selective brake specifically on cDC1s but not on the closely related cDC2s. CARM1 is an epigenetic enzyme, meaning it modifies the packaging of DNA to control which genes get turned on or off. When the researchers inactivated the Carm1 gene, cDC1s became much better at antigen cross-presentation, they activated more robustly, and they accumulated more in tumors. On top of that, a CARM1 inhibitor enhanced the ability of cDC1s to prime T cells when combined with a cancer neoantigen vaccine.
How does CARM1 do this? The team found that inhibiting CARM1 increased the accessibility of chromatin, which is the packaged form of DNA, at specific sites controlled by transcription factors called BATF3-Jun and RelA, which are critical for cDC1 function. They also found that transforming growth factor beta, a well-known immunosuppressive molecule abundant in the tumor environment, regulates CARM1 expression. This explains how CARM1 suppression could enhance the cDC1 function inside tumors without disrupting the normal steady-state balance of cDC1s throughout the body. These findings open the door to targeting CARM1 as a way to boost antitumor immunity in both mice and humans.
Next up is a paper that takes us into the molecular arms race between bacteria and viruses. From Science, July 9th, titled Bacteria sense virus-induced genome degradation via methylated mononucleotides, from Ilya Osterman at the Department of Molecular Genetics at the Weizmann Institute of Science in Rehovot, Israel.
When a bacteriophage, which is a virus that infects bacteria, invades a bacterial cell, it sometimes destroys the bacterial genome, breaking it down all the way to individual nucleotide building blocks. The bacteria need ways to detect this attack and fight back. This paper describes a newly discovered bacterial defense system called Metis, which can directly sense when the host genome is being destroyed.
Here is the elegant logic behind it. When DNA is intact, a chemical modification called methylation of deoxyadenosines occurs on the DNA polymer itself. But if the genome is being broken apart down to individual nucleotides, you suddenly get a buildup of the modified mononucleotide m6dAMP floating around freely. Metis detects this accumulation as a signal that something has gone very wrong.
There are two types of Metis. In type I Metis, sensing m6dAMP activates an enzyme called NAD+ diphosphatase, which depletes the cell of NAD+, a crucial molecule for energy and metabolism, essentially shutting down the infection process. In type II Metis, the sensor is connected to a membrane-spanning protein whose toxic activity is triggered when it detects the modified mononucleotide. The researchers also showed that Metis defense depends on the bacterium having its own DNA methylases in the first place, because without them there would be no modified mononucleotides to detect. And as is often the case in the evolutionary battle between bacteria and phages, phages can escape Metis by acquiring mutations that prevent them from degrading the host genome in the first place.
Now let us talk about how viruses on the other side of the battle evade our immune systems. Published in Science on July 9th, a paper titled Virome-wide ubiquitin ligase discovery reveals diverse mechanisms of immune evasion, from Caleb Glassman at the Department of Genetics at Harvard Medical School in Boston.
Viruses are not just passive invaders. They actively reshape the cellular environment inside their host to promote their own replication and hide from the immune system. One powerful way they do this is by using the host cell's own protein degradation machinery, called the ubiquitin-proteasome system. This system works like a molecular trash compactor: proteins are tagged with a small protein called ubiquitin, and then shredded by the proteasome. Viruses have evolved special proteins called viral ubiquitin ligases that can hijack this system to destroy host immune proteins.
The researchers applied a massive library of about ten thousand viral open reading frames across the entire known virome, which is the full collection of viruses that infect humans, to systematically discover viral ubiquitin ligases. They then mapped out what each ligase degrades and which host proteins it targets, using targeted CRISPR screens and proteomics.
They found that these viral effectors fall into three categories: canonical ligases that mimic the host's own E3 ubiquitin ligases, hijackers that redirect existing host E3 ligases for the virus's purposes, and non-canonical ligases that rewire a specific type of machinery called Cullin-RING ligase complexes. Strikingly, all of these diverse strategies tended to converge on immune-related proteins as targets, including JAK1, which is a critical signaling protein in the interferon pathway, and CUL1 beta-TrCP, which is involved in immune regulation. This tells us that no matter how different the viruses are, immune evasion is a dominant evolutionary pressure driving the development of these ubiquitin ligase strategies.
From the Proceedings of the National Academy of Sciences, published July 14th, comes a paper titled SpyCEP dismantles neutrophil immunity via disorder-driven chemokine remodeling and GAG targeting, from Rikin Lau at the Department of Life Sciences at Imperial College London.
Streptococcus pyogenes, also known as Group A Streptococcus, is a significant human pathogen responsible for conditions ranging from strep throat to life-threatening invasive infections. One of the key tools in its virulence arsenal is a protease called SpyCEP, which cleaves and inactivates chemokines like CXCL8 that would normally attract neutrophils to sites of infection. Neutrophils are the front-line soldiers of the innate immune system, so disabling their recruitment is a major advantage for the bacteria.
Using cryo-electron microscopy, NMR spectroscopy, and native mass spectrometry, the researchers investigated exactly how SpyCEP disrupts CXCL8 function. They discovered that a disordered region within SpyCEP, coming from what is called the cleaved autocatalytic maturation loop or CAML, actually mimics the receptor domains that CXCL8 normally interacts with. This region binds an allosteric site on CXCL8, forming what the researchers call a dynamic fuzzy complex, and this interaction promotes dissociation of CXCL8 dimers, which makes the chemokine more accessible for cleavage. This is quite different from how classical proteases work, which typically rely on rigid, precise recognition interfaces. Here disorder is the tool.
Additionally, the CAML region can bind glycosaminoglycans, or GAGs, which are sugar chains found on the surfaces of cells and in the extracellular matrix where CXCL8 is stored in high concentrations. By binding GAGs, SpyCEP is essentially positioning itself right next to the pools of CXCL8 it wants to destroy. The authors suggest this work could point toward anti-virulence therapies and vaccine strategies targeting SpyCEP.
Staying with PNAS, also published July 14th, is a paper titled IL-13 signaling in cDC2 is required for systemic anaphylactic responses, from Yasuyo Harada at the Division of Molecular Pathology at Tokyo University of Science.
This paper addresses one of the central mysteries of allergic disease: how does skin sensitization lead to systemic allergic responses like food allergy and anaphylaxis? This progression is called the atopic march, and it often begins with atopic dermatitis or eczema. The type 2 cytokine interleukin-13, or IL-13, is known to promote high-affinity IgE antibody production, but the exact cellular mechanisms were not fully clear.
Using a mouse model that links skin inflammation to systemic anaphylaxis, and with cell-specific deletions of the IL-13 receptor alpha 1 subunit, the researchers found that conventional dendritic cells, specifically cDC2s, and not T cells or B cells, are the essential targets of IL-13 for generating high-affinity IgE. Single-cell transcriptomics narrowed it down further, identifying a specific cDC2 subset defined by high expression of CX3CR1, Clec10a which is also known as CD301a, and CD301b also known as Mgl2.
When IL-13 signals to these cDC2s, it licenses them to become superior antigen-presenting cells, upregulating MHC class II and costimulatory molecules including CD301a, CD301b, and ICOSL. These activated cDC2s then travel from the periphery to the spleen through a CX3CR1-dependent mechanism, where they drive the differentiation of a specific type of helper T cell called IL-13-producing T follicular helper cells, or TFH13 cells. This cascade generates robust germinal center reactions and ultimately the production of pathogenic high-affinity IgE that underlies anaphylaxis. The authors describe this as an IL-13-cDC2 axis, and this mechanistic understanding helps explain why IL-13-targeted therapies like dupilumab have been so clinically effective in allergic diseases.
From the Journal of Experimental Medicine, published August 3rd, we have a paper titled Humans homozygous for rare or common hypomorphic IL23R variants are prone to tuberculosis, from Diana Olguin Calderon at the Laboratory of Human Genetics of Infectious Diseases, Necker Branch, INSERM U1163, Necker Hospital for Sick Children in Paris.
This study examines how variants in the IL-23 receptor gene, or IL23R, affect susceptibility to tuberculosis. It was already known that complete loss-of-function IL23R variants, when carried in two copies, abolish IL-23-dependent production of interferon gamma by lymphocytes including NK cells and innate-like T cells, predisposing people to infection with weakly virulent mycobacteria. But this study goes further.
The researchers found selective enrichment of homozygosity for four hypomorphic IL23R variants in their cohort of tuberculosis patients. Hypomorphic means these variants reduce but do not eliminate protein function. Three of these alleles are rare, with a minor allele frequency under one percent, designated G300V, G149R, and L372F. But the fourth variant, R381Q, was surprisingly common, with a minor allele frequency as high as ten point two percent in some populations. The variant IL-23R proteins can still dimerize with IL-12Rbeta1 and bind IL-23, but their function is impaired through reduced cell surface expression in the case of R381Q and G300V, or through conformational changes that reduce agonist efficacy. The result in all cases is impaired interferon gamma production by innate-like T cells and NK cells in response to IL-23, which creates a specific vulnerability to Mycobacterium tuberculosis while preserving immunity to less virulent mycobacteria. This is a compelling example of how human genetic variation, including relatively common variants, can shape infectious disease susceptibility.
Now from Nature Immunology, published July 8th, a paper titled ALOX15 orchestrates mitochondrial antiviral immunity and serves as a host target for anti-influenza therapy, from Jing-Yu Weng at the State Key Laboratory of Bioactive Molecules and Druggability Assessment at Jinan University in Guangzhou, China.
When viruses infect cells, they trigger cellular stress responses, and stress proteins can play important roles in antiviral defense. This study identifies one such protein: arachidonate lipoxygenase-15, or ALOX15, as a critical component of mitochondrial antiviral innate immunity.
Loss of Alox15 impairs a key signaling pathway called MAVS, which stands for mitochondrial antiviral signaling, leading to reduced type I interferon production and increased vulnerability to influenza virus. This susceptibility could be reversed by delivering Alox15 back to the lungs using adeno-associated virus vectors. In response to H1N1 and other RNA viruses including H3N2 and human coronavirus-229E, ALOX15 translocates to mitochondria, and this translocation does not require its enzymatic activity. Importantly, this mitochondrial localization was also observed in peripheral blood mononuclear cells from actual influenza-infected individuals, giving this finding human relevance.
Mechanistically, ALOX15 is recruited to mitochondria by polymerized MAVS, where it displaces a deubiquitinase called USP19 and sustains MAVS K63-linked ubiquitination and aggregation, which are critical for robust interferon signaling. The researchers then leveraged these findings to develop a therapeutic strategy combining a transcriptional activator of ALOX15 called songorine with its enzymatic inhibitor PD146176, creating a synergistic effect against influenza infection. This is a beautiful example of how understanding basic immune mechanisms can directly point toward new therapeutic approaches.
From Nature, published July 8th, a paper titled Diet-microbiome synergy underlies obesity-associated immunotherapy efficacy, from Lysanne Desharnais at the Rosalind and Morris Goodman Cancer Institute at McGill University in Montreal.
We know that the gut microbiome and obesity independently influence how well cancer patients respond to immune checkpoint inhibitors, which are a major class of cancer immunotherapy. There is even an unexpected clinical observation that patients with higher body mass index tend to show greater responses to immune checkpoint inhibitors, which has been something of a mystery. What this study does is ask how diet, obesity, and the gut microbiome all interact with each other to shape these outcomes.
Using twelve different mouse diet models that span a spectrum of obesity biology, the researchers characterized the metabolic, immune, and gut microbiota features associated with sensitivity to immune checkpoint inhibitors. They found that the obesity-associated improvements in immunotherapy response were not well correlated with metabolic dysfunction. Instead, they depended on the diet-gut axis, specifically on how different diets shape the gut microbial community.
Obesogenic diets promoted a robust and persistent gut microbial ecosystem that could even restore immune checkpoint inhibitor sensitivity after a short-term diet switch, or following fecal microbiota transplants from non-responder models. Colonizing germ-free mice with a single beneficial bacterium, Lactobacillus johnsonii, together with an obesogenic diet, synergistically promoted tumor regression through an enrichment of microbiota-derived aromatic amino acid metabolites. And in a very translationally relevant finding, fecal microbiota transplants from human donors with high body mass index enhanced immune checkpoint inhibitor efficacy compared with transplants from donors with normal body mass index. This study elegantly shows that it is not fat per se that drives better immunotherapy responses, but rather the specific microbial environment that certain diets create.
From Nature Communications, published July 8th, a paper titled Pulmonary mRNA-LNP vaccines for rapid and durable protection against bacterial infection, from Anqi Wei at the Department of Pharmacology, School of Basic Medical Sciences, Fudan University in Shanghai.
Bacterial lung infections remain a serious clinical problem, and while vaccines help, there is a vulnerable window right after vaccination before full protective immunity has developed. This paper describes a clever solution using a pulmonary mRNA lipid nanoparticle vaccine, delivered directly into the airway.
The vaccine incorporates an ionizable lipid designed to achieve high-level localized expression in the lung. When delivered intratracheally in female mice, it triggered a two-phase immune response. In the early phase, roughly one to seven days after vaccination, the vaccine primed lung neutrophils and macrophages into a transcriptionally pre-activated state, enhancing their phagocytic activity and enabling rapid antigen-independent bacterial clearance. This bridges the critical vulnerability window. In the second phase, the vaccine induced potent antigen-specific adaptive immune responses, providing sustained protection against both laboratory and clinical drug-resistant strains of Pseudomonas aeruginosa. Single-cell transcriptomics and immune profiling revealed coordinated activation of innate and adaptive immune programs. This dual-phase strategy represents a genuinely new paradigm in vaccine design that integrates innate priming with adaptive immunity development.
From the Journal of Experimental Medicine, published September 7th, a paper titled ADAR1 loss-of-function variants altering RNA editing define a new interferon-dependent psoriasis subtype, from Florence Assan at the Laboratory of Genetic of Skin Diseases, Imagine Institute, INSERM UMR1163 in Paris.
Psoriasis is a common inflammatory skin condition, but this paper reveals that some cases may be driven by a specific genetic mechanism involving RNA editing. The researchers investigated four unrelated families with early-onset plaque psoriasis, some with psoriatic arthritis, where the disease followed a monogenic inheritance pattern, meaning a single gene change was likely responsible. Importantly, all affected individuals showed a strong interferon signature in both skin and blood.
Whole-exome sequencing identified four rare heterozygous loss-of-function mutations in a gene called ADAR1, which encodes an enzyme that edits RNA molecules by converting adenosine to inosine. This type of editing is important for preventing the immune system from mistakenly recognizing the cell's own RNA as foreign. Six additional rare variants in ADAR1 were found in an independent cohort of 125 psoriasis patients. Single-cell transcriptomics identified keratinocytes and melanocytes as major sources of interferon in these patients. Functional studies confirmed that ADAR1 knockdown or expression of pathogenic ADAR1 variants reduced adenosine-to-inosine RNA editing and increased interferon-stimulated genes and inflammatory cytokines. Crucially, these effects were reversed by upadacitinib, a JAK inhibitor, and deucravacitinib, a TYK2 inhibitor, both of which are drugs already approved for psoriasis. These findings define a new IFN-dependent psoriasis subtype caused by inborn defects of ADAR1-mediated RNA editing, with clear implications for precision medicine.
From Cell Reports, July 9th, two papers worth mentioning. First, titled Myeloid MMP14 couples extracellular proteolysis to inflammatory and metabolic remodeling during obesity, from Long Shao at the Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases at the University of Texas Health Science Center in Houston. This study identifies macrophage MMP14, a membrane-bound protease called matrix metalloproteinase-14, as a key mediator linking extracellular matrix remodeling with inflammatory and metabolic dysfunction in obesity. MMP14 was found to promote inflammatory programming by increasing endotrophin generation and enhancing TLR4-NFkappaB signaling, while also reprogramming macrophage lipid metabolism. Myeloid-specific deletion of Mmp14 protected mice from high-fat diet-induced insulin resistance, dyslipidemia, hepatic steatosis, adipose inflammation, and fibrosis.
Second from Cell Reports, also July 9th, Human adenovirus protein VII inhibits type I IFN production by antagonizing viral RNA sensor RIG-I, from Pei-Hong Yu at ShanghaiTech University and the Guangzhou Laboratory. Human adenoviruses are DNA viruses, but they produce viral-associated RNAs that can be recognized by the RNA sensor RIG-I. This study shows that nucleocapsid protein VII from adenovirus can inhibit type I interferon production by preventing a host protein called TRIM25 from adding K63-linked ubiquitin chains to RIG-I, which are necessary for RIG-I activation. The mechanism involves blocking TRIM25 oligomerization, and this immunosuppressive function was found to be evolutionarily conserved across diverse human adenoviruses.
From Cell Host and Microbe, July 8th, a paper titled IL-13 signaling and I want to highlight two commentary pieces as well. The paper Sweet and sour immunity: The two faces of citrus defense in Huanglongbing from Chien-Yu Huang at the Department of Plant Pathology and Crop Physiology at LSU AgCenter discusses citrus Huanglongbing, a devastating disease caused by the bacterium Candidatus Liberibacter asiaticus. Two papers in the same issue reveal that this bacterium suppresses plant salicylic acid defense while paradoxically provoking a chronic immune overreaction that blocks the plant's vascular system. And there is also an intriguing commentary titled A repair helicase unravels the tangled web of bacterial immunity from Oksana Kotovskaya in Moscow, highlighting new work on a DNA repair protein called YprA that has been repurposed for antiviral immunity in bacteria, and the discovery of a new immunity system called ARMADA.
Before we wrap up, there are a few papers that were published without full abstracts, but that I want to make sure you know about because they come from key immunology journals or touch on important topics.
From Science, there is an erratum for the research article Granzyme A from cytotoxic lymphocytes cleaves GSDMB to trigger pyroptosis in target cells by Z. Zhou and colleagues, a correction to a previously published study on a key cell death pathway in immune defense.
From Nature Immunology, there are two papers. One is titled Tissue-resident CD8 positive T cells link pregnancy to breast cancer protection, which explores a fascinating connection between pregnancy, immune memory in tissues, and protection against breast cancer. The other is Exhausted CD8 positive T cell subsets differ a TAD, from Maegan Murphy at Washington University School of Medicine in Saint Louis, which looks at how different subsets of exhausted CD8 T cells, the kind that arise in chronic infections and cancer, are epigenetically distinct at the level of topologically associating domains.
From the Journal of Experimental Medicine, there is a correction titled LCKed in: Inborn errors of immunity in LCK reveal how TCR signaling is calibrated, from Ahmet Eken, a correction to an important piece on how signaling through the T cell receptor is regulated by the kinase LCK.
From Gastroenterology, there are two clinical case discussions worth noting. One from Colleen Kelly at Brigham and Women's Hospital, Harvard Medical School, titled The Management of Fulminant C. difficile Infection in an Immunocompromised Patient: Balancing Risk and Necessity, which tackles the real clinical challenge of managing severe Clostridioides difficile infection in patients with compromised immune systems. The other is A Kidney Transplant Recipient with Severe Chronic Diarrhea and Villous Atrophy, from Daan Kremer at the University Medical Center Groningen, a case that touches on the intersection of immunosuppression and gastrointestinal immunity.
From Cell Metabolism, Gut microbiota and metabolic control of immune checkpoint blockade in cancer from Joseph Gladstone, which complements this week's Nature paper and continues the conversation about how the gut microbiome shapes cancer immunotherapy responses. And from Cell Host and Microbe, Rare twin cysteine residues in the HIV-1 envelope variable region 1 link to neutralization escape and breadth development from Maria Hesselman, which investigates how specific structural features of the HIV envelope protein influence how antibodies recognize and neutralize the virus.
Also from Science this week there is a news piece titled As bird flu threatens, New Zealand vaccinates endangered birds, from Christina Larson, covering how the arrival of H5N1 influenza on the Australian mainland has triggered an ambitious vaccination program to protect endangered bird species in New Zealand. And British First Fleet brought smallpox to Australia from Andrew Curry, a historical piece examining how colonists likely introduced smallpox to a continent that was more densely populated than many historians had assumed.
And finally, there is a PNAS retraction: Retraction for Shaked and Frenkel, Curiouser and curiouser: Meningeal lymphoid structures in the aging brain, which reflects ongoing efforts in the scientific community to maintain integrity in the published record.
That is it for this week on KodaKoda's Weekly Immunology News. What a week it has been, from antibodies shaping brain circuits to bacterial immune systems that detect molecular fingerprints of viral attack, to new ways of thinking about cancer immunotherapy and allergic disease. As always, I hope these stories spark your curiosity and remind you just how remarkable the immune system truly is. See you next week.