3. The Mild Encephalitis subgroup of schizophrenia - An update

Major Depressive Disorder (MDD) is a heterogeneous group of disorders, of which some clinical subtypes seem to be associated with pro-inflammatory immune activation patterns, however, findings are ambiguous. The aim of this study is to further analyze if there are single clinical symptoms in MDD that are specifically related to immune activation patterns. Using RT-PCR the peripheral blood monocyte gene expression of 53 immune-relevant genes was analyzed in N = 50 MDD patients free of antidepressant medication. The gene expression was normalized to the reference gene ABL1 and is presented as the fold change relative to the gene expression of N = 46 healthy controls with no history of psychiatric diseases. The patients’ gene expression was correlated to the 17 items of the Hamilton Rating Scale for Depression (HAM-D). The HAM-D total score showed no significant correlation to any of the 53 genes. However, two symptoms (‘‘Anxiety Psychic’’ and ‘‘Somatic Symptoms Gastrointestinal’’) showed (highly) significant correlations to 21 and, respectively, 17 different genes. The other 15 symptoms showed no or up to four significant correlations. Consequently, specific clinical symptoms may play a crucial role in monocyte gene activation in MDD. Further research should focus on identifying dimensions of symptoms but also subtypes of MDD that may be distinctly associated with immune activation patterns.