Resident tissue macrophages within the normal rat iris lack immunosuppressive activity and are effective antigen-presenting cells.
Despite extensive study of the numerous immunoregulatory mechanisms that contribute to the 'immune-privileged'nature of the anterior chamber (AC) of the eye, little is known of the functional nature of antigen-presenting cells (APC) present in the tissues adjoining the AC. In the present study, we have compared the antigen-presenting capacity of dendritic cells (DC) and macrophages isolated from the normal rat iris. Whereas iris DC exhibited a potent ability to stimulate resting allogeneic T cells in MLR cultures (an in-vitro correlate of the ability to induce primary T cell responses), resident iris macrophages displayed negligible MLR-stimulatory capacity. Significantly, iris macrophages could efficiently elicit proliferation of primed antigen-specific T cells (an in-vitro correlate of the ability to act as local APC in secondary responses). This antigen-presenting activity was approximately half that of fully 'mature' iris DC and considerably greater than that of freshly isolated iris DC. A key contributor to the effectiveness of resident iris macrophage antigen presentation was considered to be the absence of lymphocytostatic control of T cell proliferation exerted by these cells. The results indicate dichotomous but complementary roles for DC (immune surveillance) and macrophages (local antigen presentation in secondary responses) in this tissue.
Steptoe
R J
RJ
Department of Anatomy and Human Biology, The University of Western Australia, Nedlands, Australia. steptoe@wehi.edu.au
McMenamin
P G
PG
Holt
P G
PG
D000818:Animals; D017951:Antigen Presentation / Q000276:immunology*; D000941:Antigens / Q000276:immunology; D002469:Cell Separation; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D003713:Dendritic Cells / Q000276:immunology*; D007498:Iris / Q000166:cytology*; D008213:Lymphocyte Activation / Q000276:immunology; D007959:Lymphocyte Culture Test, Mixed; D008264:Macrophages / Q000276:immunology*; D008297:Male; D010047:Ovalbumin / Q000276:immunology; D051381:Rats; D011917:Rats, Inbred Lew; D013601:T-Lymphocytes / Q000276:immunology
D000941:Antigens; D010047:Ovalbumin; D004247:DNA