The poor accessory cell function of macrophages in the rat may reflect their inability to form clusters with T cells.
The accessory cell functions of Ia+ alveolar and peritoneal macrophages were compared to those of splenic cells in the rat. Whereas splenic mononuclear cells and dendritic cells were excellent supporters of both MHC-restricted and nonrestricted T-cell mitogenic responses, Ia+ macrophages were inefficient antigen-presenting cells and poor supporters of lectin mitogenic responses. Binding of antigen-primed T-cell blasts by splenic cells in the presence of Con A or antigen occurred within 30 min and subsequently led to the formation of nonadherent clusters of "dendritic-like cells" and proliferating T-cell blasts. Unstimulated Ia- macrophages failed to bind T cells during 30 min of coculture but formed conjugates with T-cell blasts within 24 hr. Delayed binding did not require the presence of antigen or lectin, or the expression of Ia antigens by the macrophage, and did not lead to T-cell proliferation. Antigen-specific binding and antigen presentation, but not lectin mitogenesis, were enhanced by treating antigen-pulsed Ia+ macrophages with neuraminidase for 30 min at 37 degrees C. Neuraminidase did not augment splenic accessory cell function. Antigen-specific binding of T cells to Ia+ macrophages and accessory cell function may be enhanced by desialation of glycoproteins on the cell surface membrane.
D000818:Animals; D000921:Antibody-Producing Cells / Q000276:immunology; D000938:Antigen-Presenting Cells / Q000276:immunology*; D003208:Concanavalin A / Q000037:antagonists & inhibitors; D005260:Female; D000949:Histocompatibility Antigens Class II / Q000276:immunology; D007213:Indomethacin / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000187:drug effects; D008222:Lymphokines / Q000096:biosynthesis; D008264:Macrophages / Q000276:immunology*; D010529:Peritoneal Cavity / Q000473:pathology; D011650:Pulmonary Alveoli / Q000473:pathology; D051381:Rats; D011917:Rats, Inbred Lew; D013154:Spleen / Q000166:cytology; D013601:T-Lymphocytes / Q000473:pathology*
D000949:Histocompatibility Antigens Class II; D008222:Lymphokines; D003208:Concanavalin A; D007213:Indomethacin