Clinical and immunohistologic studies of corneal rejection in the rat penetrating keratoplasty model.

We used immunohistologic techniques with a penetrating keratoplasty model in the rat to study the mechanisms of corneal transplant rejection. Thirteen of 14 syngeneic grafts remained clear in contrast to 24 of 26 allogeneic grafts, which had a rejection reaction. Immunohistochemical studies of syngeneic grafts showed only rare inflammatory cells in the central grafts; however, a focal inflammatory reaction made up of macrophages and T-helper/inducer lymphocytes was seen surrounding the sutures and in the wound. In contrast, immunohistochemical studies of allogeneic grafts showed diffuse inflammation throughout the donor and recipient corneas with T-suppressor/cytotoxic cells, T-helper/inducer cells, and macrophages, resulting in destruction of the donor endothelium, neovascularization, and graft failure. Class II antigen expression was seen extensively on Langerhans cells, donor keratocytes, and both the donor and recipient endothelial cells. These findings emphasize the role of early nonspecific inflammation in the wound and around the sutures, and delineate the cellular immune response and class II antigen expression in corneal allograft rejection.

Clinical and immunopathological studies of pars planitis in a family.

We examined a family in which two brothers with identical HLA typing have pars planitis with snowbanking. Immunopathological studies of one of their eyes showed that in the area of snowbanking over the pars plana there was mild to moderate inflammatory cell infiltration, consisting of mostly Pan T (Leu 4+) lymphocytes. The ratio of T helper/inducer to T suppressor/cytotoxic cells was approximately 10:1. Few macrophages (OKM1+) were identified. Very few B cells and no NK cells were observed. Some retinal vessels had a perivascular infiltration consisting of mostly T lymphocytes. Most of the inflammatory cells bore class II antigens (HLA-DR+), while T cells bore few IL-2 receptors (anti-TAC+). The snowbank consisted mainly of glial elements (GFAP+) and basement membrane components (type IV collagen and laminin) with the predominant cell the Müller cell (Mü+). A site of inflammation at the iris-ciliary body junction also stained for B cells (Leu 14+). These findings suggest that the snowbank could be formed by the glial elements of the peripheral retina. The chronic inflammation in pars planitis appears to consist of helper T cells, both in the pars plana, and the retinal vasculature.

Iris lymphocytic infiltration in patients with clinically quiescent uveitis.

Iridectomy specimens from 16 patients with clinically quiet chronic uveitis were analyzed by immunoperoxidase staining and compared to control iridectomy specimens from 11 non-uveitic patients. Nine of 16 uveitis specimens and none of the control specimens demonstrated a lymphocytic infiltrate consisting of interleukin-2 receptor-negative T helper and suppressor cells (P less than .003). Class II antigens were detected in the iris stroma in all uveitis specimens and six of the controls (P less than .006). Despite a quiescent clinical state, patients with chronic uveitis have increased expression of class II antigens in uveal tissue and have significant uveal infiltration of T helper and suppressor cells. These findings in a variety of types of uveitis give additional support for the importance of delayed type hypersensitivity mechanisms in human uveitic disease.

Immunohistopathology of ocular sarcoidosis. Report of a case and discussion of immunopathogenesis.

An eye from a patient with systemic sarcoidosis and active ocular involvement was studied by the use of monoclonal antibodies and the immunoperoxidase technique to identify the subtypes of infiltrating cells and the presence of lymphokines. Large numbers of lymphoid cells reacting with anti-pan T cell (Leu-4) and anti-T helper/inducer (Leu-3a) subsets were observed around and within sarcoid granulomas. Only rare T suppressor/cytotoxic cells (Leu-2a) were observed. B lymphocytes and plasma cells were present in a few foci. Within the granuloma, T lymphocytes, macrophages, and epithelioid cells showed membrane labeling for interleukin 2 receptors and interferon gamma. We demonstrate the in vivo expression of interleukin 2 receptors and the release of interferon gamma by mononuclear phagocytes and T lymphocytes in ocular sarcoidosis, and we theorize about the activated T helper cell-derived lymphokines in macrophage activation and sarcoid granuloma formation in the eye.

Ocular immune responses. I. Priming of A/J mice in the anterior chamber with azobenzenearsonate-derivatized cells induces second-order-like suppressor T cells.

We studied the cellular immune responses to ocular anterior chamber (AC) priming of mice. A/J mice primed subcutaneously with azobenzenearsonate-coupled spleen cells (ABA-SC) manifested delayed-type hypersensitivity (DTH) in the form of footpad swelling when challenged 5 days later with the diazonium salt of ABA. Mice inoculated with ABA-SC in the anterior chamber at the time of subcutaneous priming, however, were tolerant to ABA. Subconjunctival inoculation with ABA-SC did not tolerize; rather it primed for DTH. Antibodies against ABA were not detectable in significant amounts in mice made tolerant by AC inoculation. The AC-induced tolerance was shown to result from hapten-specific T cell-mediated suppression. Suppressor T cells (Ts) arising from AC priming suppressed the efferent limb of the immune response and did not bear detectable cross-reactive idiotype (CRI) surface receptors. In these phenotypic and functional respects, AC-induced Ts differed from first-order Ts (Ts1) that result from i.v. priming. The results are discussed with respect to immune privilege and the anterior chamber of the eye.

The induction of cell-mediated immunity and tolerance with protein antigens coupled to syngeneic lymphoid cells.

A mouse model of cell-mediated immunity (CMI) and tolerance to protein antigens horse gamma globulin (HoGG) and cytochrome (Cyt C) was investigated. A reliable CMI response as measured in vivo by ear swelling or by an in vitro T-cell proliferation assay could be induced by one of two methods: (a) sensitization by antigen-complete Freund's adjuvant in the base of the tail, or (b) sensitization by s.c. injection of antigen coupled to syngeneic lymphoid cells. The in vivo response exhibited characteristic CMI parameters, delayed kinetics, and transfer by viable T cells. Prior i.v. injection of HoGG-modified lymphoid cells (HoGG-LC) or Cyt C-LC before sensitization resulted in a rapidly induced, dose-dependent, antigen-specific suppression of both in vivo and in vitro manifestations of the CMI response. In addition, tolerance in this system was transferrable by an antigen-specific suppressor T cell (Ts). The Ts were found to diminish the in vivo ear swelling reaction in recipient animals, but had no effect on the in vitro T-cell proliferative response of the recipients. In contrast to the rapid development of tolerance in donor mice (phenotypic tolerance), transferrable Ts were first demonstrable 4--7 d posttolerization. This latter result indicates that at least two mechanisms of tolerance are operative in this system: the rapid induction of clone inhibition of reactive T cells and the slower induction of Ts. These results indicate again that the mode of antigen presentation is crucial in determining the immunologic outcome. In these experiments, cell-bound proteins injected subcutaneously led to delayed hypersensitivity while the same antigens injected intravenously led to tolerance. These results are considered in the light of recent experiments which show that T cells recognize antigens on cells in association with major histocompatibility complex products. We believe the following pathways are involved. In sensitization via subcutaneous injection of HoGG-LC, antigen reaches the lymph node via lymphatic pathways which lead to immunogenic macrophage-associated presentation and the activation of delayed hypersensitivity T cells (TDH). In tolerization via intravenous injection of HoGG-LC, antigen (a) reaches the lymph node via the blood, probably directly meeting the TDH, preventing its subsequent activation by immunogenic HoGG (clone inhibition) and (b) reaches the spleen, also via the blood, activating suppressor T cells.