Serotonin can decrease IL-17 production, and IL-17 is highly elevated in depressed patients. Inflammation is elevated in depressed patients more generally, but baseline IL-17 levels specifically appear to be a good predictor for antidepressant response[1]. Anti-depressants are pretty much universally anti-neuroinflammatory.
[1]: https://pubmed.ncbi.nlm.nih.gov/28698115/