Alterations in the terminal complement pathway in leukopenic children with malignant diseases during episodes with evidence of infection

A prospective study comprising 23 children under treatment with cytostatic drugs for malignant diseases was undertaken to search for complement abnormalities during episodes with evidence of infection. Eleven patients developed 17 episodes with fever (temperature greater than or equal to 38 degrees C) (n = 13) and/or increased concentration greater than or equal to 10 mg/l) of C-reactive protein (CRP) (n = 16). Complement factor C9 increased significantly (greater than or equal to 150%) in 12/13 of the events with fever, in 16/16 with increased CRP, and in 1 additional event with normal temperature and CRP concentration. The terminal complement complex (TCC) increased excessively (37.2 units/ml) parallel to a fall in C9 and S-protein in a single patient with a lethal septic shock, and was slightly increased (2.9 units/ml) in a 2nd case who was efficiently treated. These were also the only 2 cases with verified bacterial infections. We conclude that C9 is a valuable supplement to CRP for detection of events with probable infection and that TCC is increased only in severe infection and may be of prognostic importance.