Mopuri, Rohini

Abstract Introduction/Objective Mutations in KIT and PDGFRA drive the majority of gastrointestinal stromal tumors (GIST) and inform targeted therapy selection. While single-driver mutations are typical, a subset of cases harbors multiple KIT mutations, complicating clinical interpretation. This study investigated the frequency, distribution, and inferred hierarchy of primary and secondary KIT mutations using DNA-based sequencing in a large GIST cohort. Methods/Case Report We retrospectively reviewed 579 GIST cases that underwent DNA-based next-generation sequencing using a custom panel targeting all coding exons of KIT and PDGFRA. Tumor-rich formalin-fixed paraffin-embedded (FFPE) tissue was required. In double-mutant cases, the mutation with higher variant allele frequency (VAF) was presumed to be primary. Results Mutations in KIT or PDGFRA were detected in 482/579 cases (83.2%). Among KIT-mutant cases, 28 had two mutations and one had three. Secondary mutations frequently occurred in exons 13, 14, and 17 and were significantly more common in non-gastric tumors (p < 0.0001). Primary mutations most often involved exon 11. Conclusion VAF analysis enabled classification of mutation hierarchy in cases with multiple KIT mutations. The distinct anatomical and exon-specific distribution of primary vs. secondary mutations highlights their potential therapeutic implications and warrants further study.

This study reveals a novel role for Treg-derived IL-6R in supporting epithelial repair. Despite preserved immune-suppressive capacity, deletion of IL-6R from Tregs impairs epithelial transcription and worsens injury in colitis. We demonstrate that human intestinal organoids preferentially respond to trans- over classic IL-6 signaling. These findings introduce a Treg-specific role in immune-epithelial cross talk relevant to mucosal healing and inflammatory bowel disease.

Intrathecal synthesis of central nervous system (CNS)-reactive autoantibodies is observed across patients with autoimmune encephalitis (AE), who show multiple residual neurobehavioral deficits and relapses despite immunotherapies. We leveraged two common forms of AE, mediated by leucine-rich glioma inactivated-1 (LGI1) and contactin-associated protein-like 2 (CASPR2) antibodies, as human models to comprehensively reconstruct and profile cerebrospinal fluid (CSF) B cell receptor (BCR) characteristics. We hypothesized that the resultant observations would both inform the observed therapeutic gap and determine the contribution of intrathecal maturation to pathogenic B cell lineages. From the CSF of three patients, 381 cognate-paired IgG BCRs were isolated by cell sorting and scRNA-seq, and 166 expressed as monoclonal antibodies (mAbs). Sixty-two percent of mAbs from singleton BCRs reacted with either LGI1 or CASPR2 and, strikingly, this rose to 100% of cells in clonal groups with ≥4 members. These autoantigen-reactivities were more concentrated within antibody-secreting cells (ASCs) versus B cells ( P < 0.0001), and both these cell types were more differentiated than LGI1- and CASPR2-unreactive counterparts. Despite greater differentiation, autoantigen-reactive cells had acquired few mutations intrathecally and showed minimal variation in autoantigen affinities within clonal expansions. Also, limited CSF T cell receptor clonality was observed. In contrast, a comparison of germline-encoded BCRs versus the founder intrathecal clone revealed marked gains in both affinity and mutational distances ( P = 0.004 and P < 0.0001, respectively). Taken together, in patients with LGI1 and CASPR2 antibody encephalitis, our results identify CSF as a compartment with a remarkably high frequency of clonally expanded autoantigen-reactive ASCs whose BCR maturity appears dominantly acquired outside the CNS.