ORIGIN AND STEADY-STATE TURNOVER OF MAJOR HISTOCOMPATIBILITY COMPLEX CLASS II-POSITIVE DENDRITIC CELLS AND RESIDENT-TISSUE MACROPHAGES IN THE IRIS OF THE RAT EYE
Rj. Steptoe et al., ORIGIN AND STEADY-STATE TURNOVER OF MAJOR HISTOCOMPATIBILITY COMPLEX CLASS II-POSITIVE DENDRITIC CELLS AND RESIDENT-TISSUE MACROPHAGES IN THE IRIS OF THE RAT EYE, Journal of neuroimmunology, 68(1-2), 1996, pp. 67-76
Recent studies have identified distinct but co-existing networks of re
sident tissue macrophages and MHC class II-positive DC present in tiss
ues bordering the anterior chamber of the eye, a site classically rega
rded as 'immune-privileged'. As the DC network, present at approximate
ly 500 cells/mm(2), accounts for virtually all MHC class II immunostai
ning in these tissues and possesses potent capacity to stimulate prima
ry allogenic responses in vitro, it is proposed that these cells may p
lay an important role in immune surveillance of the anterior chamber.
Tissue macrophage and DC population kinetics in the iris were examined
by using X-irradiation exposure to interrupt the steady-state renewal
of these cells by haematopoietically derived precursors. MHC class II
-positive iris DC exhibited a half-life of approximately 3 days, a rap
id turnover rate which closely resembled that of DC present in mucosal
epithelia. In contrast, the resident tissue macrophage population dis
played a considerably slower turnover (half-life of 10-12 days) compar
able to that of epidermal Langerhans cells in the present study, Bone
marrow transplantation studies confirmed the haematopoietic origin of
the iris DC population. The present study provides the first estimates
of the steady-state population kinetics of antigen-presenting cell po
pulations in the iris and has important implications for understanding
the role of these cells in immunological homeostasis of the anterior
chamber.