Our finding of shared genetic links between lymphocyte count and schizophrenia at the MHC region through multiple independent pathways may support a pathogenic role for immune dysfunction in development of schizophrenia, exemplified by the recent identification of key complement factor genes (C4A, C4B) as drivers of schizophrenia (Sekar et al., 2016). Here, C4B is linked to schizophrenia.