Studies on the induction of anterior chamber-associated immune deviation (ACAID). II. Eye-derived cells participate in generating blood-borne signals that induce ACAID

Abstract

Despite an ever increasing body of information concerning general in vivo immune reactivity to exogenous Ag, relatively little is known concerning regional tissue influences on these responses. One expression of regionally distinct immune regulation is the deviant form of systemic immunity induced after the introduction of Ag, such as BSA, into the anterior chamber of the eye--anterior chamber-associated immune deviation (ACAID). ACAID is characterized by a selective, systemic immune deficiency in which both Ag-specific delayed hypersensitivity (DH) and complement-fixing antibody production are impaired by populations of Ts lymphocytes, although other immune effector modalities are preserved. Recent evidence demonstrates that the blood of mice that receive an anterior chamber injection of BSA 48 h earlier contains leukocytes capable of inducing cell-mediated Ag-specific efferent suppression of DH similar to that seen in mice with ACAID. Additional analysis of these bloodborne suppression-inducing leukocytes revealed them to express the mature macrophage/monocyte marker F4/80. On the basis of these findings, we wished to determine the source of the ACAID-inducing cells present in the peripheral blood of mice after anterior chamber inoculation of BSA. The data reveal that cells harvested from the normal eye are capable of selective induction of DH suppressive activity similar to that seen in ACAID. Interestingly, this property is unique to F4/80 expressing cells of the iris and ciliary body (I/CB). F4/80- I/CB cells do not possess this property. Although the F4/80 expressing cells that are present in extraocular sites do not constitutively possess ACAID-inducing properties, exposure of these cells to the anterior chamber microenvironment endows them with this ability. Finally, I/CB cells exposed to Ag in situ, via direct anterior chamber Ag inoculation, induce suppressed Ag-specific DH reactivity when infused into naive syngeneic recipients--a form of systemic immune deviation similar to that seen in mice with ACAID. The results presented here represent the first in vivo description of APC, altered by factors in a local microenvironment, that can initiate a systemic immune response characterized by Ag-specific immune suppression.