Possible Involvement of Transglutaminase in Endocytosis and Antigen Presentation

Abstract

Experiments using mice were carried out to determine whether internalization of antigen is necessary for subsequent antigen presentation by accessory cells using monoamines which are known transglutaminase (TGase) inhibitors. Endocytosis for immune complexes via Fc receptors such as sheep erythrocytes coated with IgG class antibody was different from receptor-independent endocytosis for soluble protein such as horseradish peroxidase in the sensitivity to monoamines; methylamine inhibited the receptor-dependent endocytosis of immune complexes at a concentration of > 20 mM and the receptor-independent endocytosis of HRP at 2 mM, while dansylcadaverie (DC) inhibited both at a concentration of 100 .mu.M. Antigen-specific T cell proliferation to splenic adherent cells pulsed with dinitrophenol-9.6 ovalbumin was blocked strongly by DC as well, but weakly by methylamine. Thus, antigen presentation possibly requires internalization of antigen by a mechanism such as receptor-dependent endocytosis for the subsequent reexpression of antigen on membranes, TGase activity was high in peritoneal exudate and spleen-adherent cells, both of which have accessory cell activities for lymphocytes, suggesting that TGase might be involved intimately in receptor-dependent endocytosis and subsequent antigen presentation.