biostudies-literatureMeng QZhejiang Provincial Key Project of Aquaculture New Varieties Breeding3067https://www.ebi.ac.uk/biostudies/studies/S-EPMC12610153biostudies-literatureUnknown15(21)Heat stress typically suppresses systemic immunity in fish; however, its effects on the brain-an organ traditionally regarded as immune-privileged-remain unclear. In this study, we performed histopathological examination and RNA-seq analysis on the brains of juvenile largemouth bass (<i>Micropterus salmoides</i>) exposed to control (28 °C) and elevated (36.5 °C) water temperatures for 8 weeks. Histological analysis revealed distinct cytoarchitectural and pathological changes in specific brain regions. RNA-seq analysis identified a total of 1240 differentially expressed genes, with 22 heat shock protein genes notably showing significant up-regulation. The immune system-associated genes emerged as the most prominently affected category. Gene set enrichment analysis (GSEA) based on Kyoto EncyAnimals : an open access journal from MDPILong-Term Heat Stress Triggers Immune Activation and Cell Death Remodeling in the Brain of Largemouth Bass (<i>Micropterus salmoides</i>).PMC126101532021C02069-2Peng YLi JGuo JMeng QTao YLi FHuang HXun CChen XZhou FfalseLong-Term Heat Stress Triggers Immune Activation and Cell Death Remodeling in the Brain of Largemouth Bass (<i>Micropterus salmoides</i>).Heat stress typically suppresses systemic immunity in fish; however, its effects on the brain-an organ traditionally regarded as immune-privileged-remain unclear. In this study, we performed histopathological examination and RNA-seq analysis on the brains of juvenile largemouth bass (<i>Micropterus salmoides</i>) exposed to control (28 °C) and elevated (36.5 °C) water temperatures for 8 weeks. Histological analysis revealed distinct cytoarchitectural and pathological changes in specific brain regions. RNA-seq analysis identified a total of 1240 differentially expressed genes, with 22 heat shock protein genes notably showing significant up-regulation. The immune system-associated genes emerged as the most prominently affected category. Gene set enrichment analysis (GSEA) based on Kyoto Ency2025-01-01T00:00:00Z2025 Oct2026-05-17T03:10:49.885Z2026-05-17T03:07:51.148ZS-EPMC126101534122739810.3390/ani15213067