Modeling Prenatal Immune Activation in Human Brain Organoids Uncovers IL-6-Dependent Interneuron Dysmaturation.

Prenatal inflammation has been associated with an increased likelihood of the child developing neurodevelopmental conditions, such as autism spectrum disorder (ASD). Several pro-inflammatory cytokines are significantly upregulated and play critical roles during immune activation, with interleukin-6 (IL-6) being particularly prominent. However, the specific impact of elevated IL-6 levels on human neural development remains to be elucidated. To address this, we established a human pluripotent stem cell-based forebrain organoid model enriched for multiple interneuron lineages, validated through immunohistochemistry and transcriptomic alignment with human fetal reference datasets. We showed IL-6 responsiveness via the activation of the JAK/STAT pathway and characterized downstream effects using bulk and single-nucleus RNA sequencing (RNA-seq). Bulk RNA-seq at the end of IL-6 exposure uncovered activation of inflammatory pathways, upregulation of MHC-I machinery, and early disruption of GABAergic signaling programs. Notably, single-nucleus RNA-sequencing performed one month after IL-6 withdrawal revealed a persistent inflammatory transcriptional signature across interneuron development, accompanied by accelerated progression through maturation stages and altered interneuron subtype output. Together, these findings demonstrate that transient prenatal IL-6 exposure is sufficient to reshape human interneuron fate specification and maturation trajectories, providing mechanistic insights into neuroimmune contributions to ASD.