Preferential activation and depletion of the alternative complement pathway by burn injury.

Complement levels of eight adult burn patients (25% to 90% body surface area) were studied upon admission to a burn unit and sequentially for one week. Mean classical pathway titers (CH50) were 49% below the normal mean, while hemolytic C4 titers were reduced by 53% and C3 by 43%. However, the alternative pathway titer was reduced by more than 90%, suggesting preferential depletion of this pathway. This depletion was associated with sepsis, pneumonia, and "shock lung." Alternative pathway deficiency was still present one week postburn, and may contribute to the susceptibility of burn patients to bacterial sepsis.