From our data and those from previous studies on pneumococcal meningitis, complement C3 is increased in SPP samples8, 9, 40 and here, we demonstrate an increase in concentration of other components of the complement system from the classical pathway (complement C4-A (UniprotKB P0C0L4), Complement C1r subcomponent (UniprotKB P00736), complement factor I (UniprotKB P05156), Complement C2 (UniprotKB P06681)) and the alternative pathway (complement factor B (UniprotKB P00751) and complement factor H (UniprotKB P08603)). Here, C3 is linked to pneumococcal meningitis.