Scientists at University Medical Center Utrecht have identified a previously underappreciated mechanism that helps immune cells respond rapidly to infection. Using long-read RNA sequencing, the team demonstrates that alternative RNA splicing plays a central role in shaping immune responses. The findings, published in Nature Communications, may open the door to more targeted therapies for immune-mediated diseases including rheumatoid arthritis and lupus.
The study focused on monocytes, innate immune cells that act as first responders to pathogens. While previous research has largely examined changes in overall gene expression, this study focused on RNA isoforms—the different transcript variants a single gene can produce. The team generated a comprehensive map of full-length RNA transcripts in human monocytes before and after activation with bacterial components, identifying more than 24,000 isoforms, the majority of which have never been described.
A key finding is that immune activation triggers widespread isoform switching. Rather than simply turning genes on or off, monocytes shift toward producing longer, fully functional RNA variants more likely to be translated into proteins. These isoforms contain complete coding sequences, fewer non-coding interruptions, and greater structural complexity—features associated with more effective protein production.
"In our study we also confirmed that these RNA changes have real functional consequences. By integrating data on protein synthesis and ribosome activity, we demonstrated that the observed isoform shifts are linked to increased production of immune effector proteins. This shows that alternative splicing directly enhances the cell's ability to respond to infection or inflammation," Jorg van Loosdregt Ph.D., principal investigator of the study.
The findings carry implications for immune-mediated diseases such as rheumatoid arthritis and lupus, conditions previously linked to genetic variation affecting RNA splicing. The study adds a new layer of insight, suggesting that disease mechanisms may depend not only on which genes are expressed, but on which isoforms are produced and how efficiently they are translated into proteins.
Van Loosdregt noted that traditional methods may overlook critical changes that only become visible with full-length RNA analysis, and that the adoption of long-read sequencing technologies could transform research into immune function and disease mechanisms.
Co-author Bas Vastert added: "For patients with an immune-mediated disease, the findings point toward new therapeutic opportunities. If harmful immune responses are driven by specific splicing patterns, these processes could potentially be targeted. Emerging approaches, such as antisense oligonucleotides or drugs that influence splicing factors, may enable more precise modulation of the immune system and the development of targeted treatments for immune-mediated diseases in the future."
The study focused on monocytes, innate immune cells that act as first responders to pathogens. While previous research has largely examined changes in overall gene expression, this study focused on RNA isoforms—the different transcript variants a single gene can produce. The team generated a comprehensive map of full-length RNA transcripts in human monocytes before and after activation with bacterial components, identifying more than 24,000 isoforms, the majority of which have never been described.
A key finding is that immune activation triggers widespread isoform switching. Rather than simply turning genes on or off, monocytes shift toward producing longer, fully functional RNA variants more likely to be translated into proteins. These isoforms contain complete coding sequences, fewer non-coding interruptions, and greater structural complexity—features associated with more effective protein production.
"In our study we also confirmed that these RNA changes have real functional consequences. By integrating data on protein synthesis and ribosome activity, we demonstrated that the observed isoform shifts are linked to increased production of immune effector proteins. This shows that alternative splicing directly enhances the cell's ability to respond to infection or inflammation," Jorg van Loosdregt Ph.D., principal investigator of the study.
The findings carry implications for immune-mediated diseases such as rheumatoid arthritis and lupus, conditions previously linked to genetic variation affecting RNA splicing. The study adds a new layer of insight, suggesting that disease mechanisms may depend not only on which genes are expressed, but on which isoforms are produced and how efficiently they are translated into proteins.
Van Loosdregt noted that traditional methods may overlook critical changes that only become visible with full-length RNA analysis, and that the adoption of long-read sequencing technologies could transform research into immune function and disease mechanisms.
Co-author Bas Vastert added: "For patients with an immune-mediated disease, the findings point toward new therapeutic opportunities. If harmful immune responses are driven by specific splicing patterns, these processes could potentially be targeted. Emerging approaches, such as antisense oligonucleotides or drugs that influence splicing factors, may enable more precise modulation of the immune system and the development of targeted treatments for immune-mediated diseases in the future."