Stimulation of neutrophil elastase and myeloperoxidase release by IgG fragments
Human leucocyte elastase (HLE) cleaves IgG into Fab and Fc fragments. The Fc fragment bears an elastase‐specific antigen and has previously been reported to be found in synovial fluid during rheumatoid arthritis, In addition, biological activity of clastasc‐specific Fc fragments has been described in modulating granulocyte oxidative metabolism. To investigate further regulatory effects of the elastase‐induced IgG cleavage products, we tested the elaslase and myeloperoxidase release of granulocytes. IgG fragments induce no enzyme release of unstimulated neutrophils. But elastase and myeloperoxidase release of cytochalasin b/FMLP‐treated neutrophils is stimulated in a dose‐dependent manner by the Fab fragments. The extent of stimulation depends on stimulus concentration and is at its maximum for low (e.g. 2.5 × 10−8m) FMLPconcentration. Ten nanomoles Fab/4 × 106 PMN augment elastase release to 206% and myeloperoxidasc release to 155% after prestimulation with 2.5 × 10−8 m FMLP. Fc fragments stimulate elaslasc release to 162% but no MPO release. Untreated IgGl and analog Fab and Fc fragments produced by papain cleavage react similarly. Elastase‐generated IgG fragments may therefore up‐regulate their concentration by stimulating elastase release. The concomitantly stimulated release of myeloperoxidase may influence bactericidal activity and termination of oxidative burst.