Breakthrough in Immunology: The Discovery of Nucleocytosis

The immune system has long been known for its remarkable ability to detect and respond to threats, but a recent study has uncovered a previously unknown process that sheds new light on how it interacts with our own dying cells. Researchers have identified 'nucleocytosis,' a mechanism where macrophages—key immune cells—selectively extract nuclear DNA from dying cells, activating the cGAS-STING pathway to trigger type I interferon (IFN-I) responses. This discovery, published in the prestigious journal Nature Communications on February 18, 2026, challenges traditional views of cell death and immune activation.

While the lead researchers hail from Japan's University of Tokyo, the findings have resonated strongly in Brazil's scientific community, where universities like the University of São Paulo (USP) and Fiocruz are at the forefront of immunology research on autoimmune diseases. This process could explain persistent inflammation in conditions like systemic lupus erythematosus (lupus), which affects thousands in Brazil annually.

What is Nucleocytosis? Defining the Process

Nucleocytosis (from 'nucleus' and 'cytosis,' referring to cellular movement) is distinct from phagocytosis, where immune cells engulf entire dying cells. Instead, macrophages form protrusion-like structures to directly penetrate the nucleus of a dying cell and pull out DNA fragments. This extracted DNA then enters the macrophage's cytosol, where it binds to cyclic GMP-AMP synthase (cGAS), a sensor protein. cGAS produces cyclic GMP-AMP (cGAMP), activating stimulator of interferon genes (STING), which leads to IFN-I production and downstream inflammatory signaling.

The process begins with lysosomal malfunction in target cells, often induced by cationic amphiphilic drugs (CADs) like hydroxychloroquine (HCQ). This causes proton loss and inhibition of palmitoyl-protein thioesterase 1 (PPT1), triggering cell death and calreticulin (CALR) accumulation in the nucleus. CALR acts as an 'eat-me' signal, guiding macrophages to the nucleus.

Step-by-Step Mechanism of DNA Extraction

1. Lysosomal Dysfunction: Exposure to CADs disrupts lysosomal pH and inhibits PPT1, halting lipid degradation and causing cell stress. 2. Cell Death Initiation: Dying cells (apoptotic or necrotic) accumulate CALR in the nucleus, serving as a beacon. 3. Macrophage Engagement: Macrophages extend protrusions (possibly tunneling nanotube-like) to contact the nucleus. 4. DNA Extraction: Nuclear DNA is selectively pulled out, reducing nuclear DNA intensity in dying cells while increasing cytosolic DNA in macrophages. 5. cGAS Activation: Cytosolic DNA activates cGAS, producing cGAMP. 6. IFN-I Response: STING, TBK1, and IRF3 phosphorylate, inducing IFN-β secretion from a subset of macrophages.

• Live-cell imaging confirmed secretion correlates with DNA transfer.
• Single-cell RNA-seq showed macrophage-specific IFN-β expression.

This precise sequence highlights nucleocytosis as a regulated immune function, not random debris uptake.

The Research Team and University of Tokyo's Role

Led by Project Lecturer Hideo Negishi and Professor Ken J. Ishii at the Institute of Medical Science, University of Tokyo, the team used advanced techniques like live-cell imaging of secretion (LCI-S) and scRNA-seq. "The most striking aspect was realizing cells possess an entirely new way to handle nuclear contents," said Negishi.

Ishii noted motivations from COVID-19 drug mechanisms. Collaborators included RIKEN and Yokohama City University, showcasing Japan's higher education excellence in quantitative biosciences.

Publication Impact in Nature Communications

DOI: 10.1038/s41467-026-68839-w. The paper demonstrates HCQ induces STING-dependent IFN-I in lung macrophages in vivo, without systemic effects. Experiments with PPT1 inhibitors and proton blockers confirmed synergy.

This high-impact venue (cited in antiviral and autoimmune contexts) elevates the discovery's profile, inspiring similar rigorous studies worldwide.

Photo by Lucas Vasques on Unsplash

Implications for Autoimmune Diseases Like Lupus

Nucleocytosis explains how self-DNA drives chronic IFN-I in lupus, Aicardi-Goutières syndrome. In Brazil, lupus affects ~1 in 2,000, with Fiocruz researching genetic factors. HCQ, used in lupus, may paradoxically induce local IFN-I via nucleocytosis, balancing TLR inhibition.

New targets: Block CALR relocation or protrusions for therapy.

Brazilian Higher Education's Contributions to Immunology

Brazil boasts world-class immunology research. USP's Center for Research on Inflammatory Diseases (CRID) at Ribeirão Preto studies lupus mechanisms, identifying altered gene expression in lymphocytes.

Fiocruz's Clinical Immunology Lab investigates inflammatory diseases, while ICB-USP covers autoimmunity to cancer. This nucleocytosis finding could integrate with Brazilian work on cGAS-STING in schistosomiasis.

Opportunities abound for collaborations, with university jobs in Brazil's immunology sector.

Therapeutic Potential and Drug Repurposing

CADs like HCQ show antiviral promise via nucleocytosis (e.g., against Ebola). For cancer, inducing it enhances anti-tumor IFN-I. PPT1 inhibitors + lysosomotropics could boost immunotherapy.

• Local lung IFN-I without systemic toxicity.
• Potential for lupus: Modulate to reduce aberrant activation.

Future Outlook and Research Directions

Upcoming studies may explore nucleocytosis in human models, specific macrophage subsets, and regulation (e.g., Rho kinase). In Brazil, integrating with genomic studies at USP could personalize lupus treatments.

Global higher ed benefits: Trains students in advanced imaging, scRNA-seq.

Impacts on Higher Education and Careers

This discovery exemplifies interdisciplinary higher ed: biosciences, imaging, bioinformatics. Brazilian universities like UFSC (lupus genetics) position graduates for global roles.

Check Rate My Professor for top immunology faculty or higher ed career advice.

Photo by SUBVERSO ✦ AC on Unsplash

Conclusion: A New Chapter in Immune Research

Nucleocytosis redefines self-DNA immunity, with profound implications for diseases prevalent in Brazil. As universities advance, explore higher ed jobs, university jobs, rate professors, and career advice to join this frontier.