Limited cleavage of human immunoglobulins by elastase of human neutrophil polymorphonuclear granulocytes. Possible modulator of immune complex disease.

Human polymorphonuclear lysosomal granules contain a neutral protease which is capable of digesting human immunoglobulins. The protease is located in the azurophil granules and enzymatically cleaves IgG, producing a Fab-like piece which is recoverable. The Fc-like fragment is not crystallized. The Fab-like fragment competes effectively for ligands formed by native antibody from which the fragments were produced.