Among these 46 immune system genes, 12 of them (or 26%) were previously associated with obesity-related traits and 10 of them had expression altered by antipsychotics only in the weight gain group (LTF, LCN2, MMP8, OLR1, MPO, LILRA3, AIM2, LILRA5, S100A9, and CHIT1). Here, CHIT1 is linked to obesity due to melanocortin 4 receptor deficiency.