Resident tissue macrophages within the normal rat iris lack immunosuppressive activity and are effective antigen-presenting cells

R. J. Steptoe, P. G. McMenamin, P. G. Holt

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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.

Original languageEnglish
Pages (from-to)177-187
Number of pages11
JournalOcular Immunology and Inflammation
Issue number3
Publication statusPublished - 1 Dec 2000
Externally publishedYes


  • Anterior chamber
  • Antigen-presenting cell
  • Dendritic cell
  • Iris
  • Macrophage

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