C4A and schizophrenia: The four complement components for which we found evidence of upregulation in schizophrenia cases were: CR1, CR2, CD55, and C3. CR1 is expressed on most blood cells and has a high affinity for complement components (C1q, C3 and C4).45 CR1 expression on the surface of lymphocytes, monocytes and neutrophils was found to be higher in schizophrenia cases than in controls,46 as its messenger RNA was in the current study.