Journal of Experimental Medicine, Vol 157, 1184-1196, Copyright © 1983 by Rockefeller University Press
Selective proteolysis of immunoglobulins by mouse macrophage elastase
MJ Banda, EJ Clark and Z Werb
Mouse macrophage elastase, a metalloproteinase secreted by inflammatory
macrophages, catalyzed the limited proteolysis of selected subclasses of
mouse immunoglobulins, including monomeric IgG2a, IgG3, and some forms of
IgG2b. Mouse IgG1 was resistant to elastase degradation; however, human
IgG1 was degraded. IgG3 in immune complexes was cleaved in a manner similar
to that of monomeric IgG3. Degradation by macrophage elastase was limited
to the heavy chain, resulting in products that did not compete for binding
to the macrophage Fc receptor. Macrophage elastase usually produced a
pepsin-like rather than a papain-like pattern of proteolysis, resulting in
the release of F(ab')2 and Fc' subfragments. This degradation of IgG
differed from the papain-like cleavage of IgG by granulocyte elastase.
Macrophage elastase degraded papain-generated Fc fragments of IgG2a into
multiple fragments. Therefore, macrophage elastase at concentrations found
in culture medium has the potential to regulate some aspects of cellular
events associated with immunoglobulins.