[The role of complement and specific antibodies in the development and defense mechanism of sepsis and septic shock]

Abstract

Sepsis, abscess formation or development of purulent exudates in closed cavities expresses insufficient host defense against pyogenic infections. An attempt is made to analyse the reasons for diminished host resistance and/or increased virulence of the invading microbes. While the role of cellular defense mechanisms is not considered, a number of humoral components, such as lysozymes glycolipids, lactoperoxidase, fibronectin, esterases and haptoglobin, participate in efficient defense. Special emphasis is placed on serum complement, both with regard to its unspecific but nevertheless efficient alternative pathway, and with respect to its phylogenetically much more recent classical pathway. Recognition of bacteria by either mechanism of complement activation leads to C3b deposition on the microbial surface for efficient opsonization, while the juxtaposition of at least two molecules of antibodies contained in the immunoglobulin fraction of plasma safely leads to complement activation via the classical pathway. Therefore, specific recognition of bacteria by immunoglobulin-antibodies remains the core of anamnestic antimicrobial defense, the more so since some antibodies may also confer on the bacterial surface the capacity to activate the alternative pathway. The recent description of monoclonal antibody directed at bacteria relevant in sepsis opens perspectives in the near future when such components will eventually be used for therapeutic purposes, along with antibodies also directed towards the pathogenetic bacterial products endo- and exotoxin.