C4A and inborn error of immunity: In this study, the different genes that were expressed in the “primary immunodeficiency” were mainly the components of complement system, with down-regulated expression of C1s-like, C2, C3, C4, c8g.1, C9, complement component (3b/4b) receptor 1-like, complement receptor type 2-like, complement factor H and hemolytic complement.