C4A and infection: The diagnosis of infection is supported by the presence of shaking chills, leukocytosis and/or neutrophilia (especially in the absence of steroid therapy), increased numbers of band forms or metamyelocytes on peripheral blood smear, and concomitant immunosuppressive treatment.11 Conversely, active SLE is suspected in cases of leukopenia (not explained by cytotoxic therapy), normal or only slightly increased C-reactive protein (CRP), and coexisting serological activity (low complement factors C3/C4, elevated anti-DNA titres).