TDO2 and schizophrenia: More recently, Kindler et al. 202046 found that KYNA levels, the KYN:TRY ratio, and the transcripts of TDO and KATI/II were increased in the prefrontal cortex of a “high cytokine schizophrenia subgroup” identified by measurements of proinflammatory cytokine mRNA, and there was a positive correlation between KAT and glial fibrillary acidic protein mRNA.