Cathy G. McAllister

Retinal vascular endothelium expresses fibronectin and class II histocompatibility complex antigens in experimental autoimmune uveitis.

To analyze the role of the retinal vascular endothelial cells in the development of experimental autoimmune uveitis (EAU), we studied the presence of Ia antigen and FN in retinal vessels of Lewis rats immunized with retinal S antigen. Immunopathologic studies were performed on frozen tissues obtained during various stages of the disease. Our results show that Ia antigen was not present in the normal rat retina, and there was very little FN present in a few retinal vessels. One to two days prior to the histologic and clinical onset of EAU, FN was found to be increased in the retinal vessels. Ia antigen was found to be present in the retinal vessels coincident with the first signs of cellular infiltration. During the stage of maximal cellular infiltration, FN was present diffusely throughout the retina, as well as in the subretinal space, and Ia antigen was found diffusely in the cellular infiltrate. Therefore, FN and Ia antigen reflect the immunomodulation of vascular endothelial cells in EAU, which may be very important in the pathogenesis of retinal S antigen-induced uveitis. Two possible mechanisms for the role of the activation of the retinal vascular endothelium in the development of retinal inflammation in uveitis are discussed.

Rat T-cell lines specific to a nonimmunodominant determinant of a retinal protein (IRBP) produce uveoretinitis and pinealitis

Rat lymphocyte lines were established, with specificity toward two synthetic peptides derived from the interphotoreceptor retinoid-binding protein (IRBP), which specifically localizes in the retina and pineal gland. One of the peptides, R4, is immunopathogenic, producing experimental autoimmune uveoretinitis (EAU) and pinealitis (EAP) in immunized rats, while the other peptide, R3, exhibits no detectable immunopathogenicity in rats. The cell lines carry surface markers specific for the helper/inducer subset of T-lymphocytes. When tested by the proliferation assay, the line cells demonstrated major histocompatibility-restricted vigorous responses against the immunizing (homologous) peptide, but failed to recognize the intact IRBP molecule. This finding is in line with other data indicating that peptides R3 and R4 are nonimmunodominant determinants of IRBP for the Lewis rat. Yet, the cell lines specific for R4 were highly immunopathogenic, producing EAU and EAP in naive rats at numbers as low as 0.25 x 10(6), with histopathological changes similar to those induced by active immunization with this peptide. The immunological capacity of the cell lines was further demonstrated by the finding that spleen cells from recipient rats of these lines responded well against the homologous peptides. The uniqueness of this system, in which lymphocytes specific toward a nondominant determinant are immunopathogenic, is underscored and the possible mechanisms of disease induction are discussed.

Dual effects of pertussis toxin on lymphoid cells in culture

Pertussis toxin (Ptx), a component of Bordetella pertussis, is responsible for many of the biological activities of this bacterium, including its potent adjuvant capacity. In attempt to better understand the Ptx activity on the immune response in vivo, we have examined the effect of Ptx on certain lymphoid cell responses in vitro which could be targets for the adjuvant activity of this molecule. Ptx was found to stimulate a variety of cell responses which include (a) increased production and release of interleukin-1 (IL-1) by human monocytes and murine macrophages; (b) co-mitogenesis, in combination with IL-1, in cultures of murine thymocytes; (c) mitogenesis in cultures of various peripheral lymphocytes; (d) increased production of IL-2 in cultures of human blood lymphocytes and rodent splenocytes; and (e) elevated release of IL-3 in cultures of murine spleen cells. In addition to its stimulatory effects, however, Ptx was found to inhibit responses of both mononuclear phagocytes and lymphocytes to other stimuli. Most activities of Ptx in vitro were achieved at the optimal concentration range of 1-10 micrograms/ml, which is 100-1000 times higher than that showing adjuvant effects in vivo. Possible explanations for the dual effect of Ptx and for the discrepancy in doses optimal for the effects in vivo and in vitro are discussed.

The effects of pertussis toxin on the induction and transfer of experimental autoimmune uveoretinitis

Experimental autoimmune uveoretinitis (EAU), an intraocular inflammatory disease, is induced in experimental animals by immunization with a retinal specific antigen, S-antigen (S-Ag), emulsified in complete Freunds adjuvant (CFA). The induction of EAU is enhanced by treating S-Ag-immunized animals with Bordetella pertussis. This study examined the effects of a purified component of B. pertussis, pertussis toxin (Ptx), on EAU induction as well as the mode of action of this toxin. Treatment of Lewis rats with Ptx concurrent with S-Ag and CFA enhanced EAU induction as shown by an earlier onset of disease, increased severity of ocular changes, and the reduction of the threshold amount of S-Ag needed for EAU induction. Treatment with Ptx selectively enhanced delayed-type hypersensitivity responses to S-Ag but did not affect specific antibody production. The mode of action of Ptx was analyzed by using the adoptive transfer of EAU by sensitized lymphocytes. Ptx treatment of donor rats enhanced the capacity of lymphocytes to transfer EAU. However, Ptx treatment of recipient rats on the day of cell transfer resulted in a delay in the onset of disease. These results indicate that Ptx enhances the immunopathogenic processes of EAU by enhancing lymphocyte activation and/or increasing their pathogenic activities.

Differential effects of cyclosporins A and G on functional activation of a T-helper-lymphocyte line mediating experimental autoimmune uveoretinitis

The effect and relative efficiency of cyclosporin A (CsA) and cyclosporin G (CsG) on suppressing the activation of primed autoimmune rat T-helper lymphocytes were assayed. The autoimmune T-helper cells (ThS) are a long-term line specific to the retinal soluble antigen (SAg) and can adoptively transfer experimental autoimmune uveoretinitis (EAU), after in vitro reactivation with antigen or mitogen, to naive syngeneic hosts. Antigen-driven production of interleukin-2 (IL-2) and antigen-driven proliferation were inhibited in a dose-dependent manner and to a similar extent at each of the respective cyclosporin concentrations. CsA was 8-10 times more potent than CsG, with ID50-CsA occurring at 0.5 to 2 ng/ml, and ID50-CsG at 5 to 20 ng/ml, depending on the experiment and the cyclosporin batch. Addition of exogenous lymphokines in the form of rat spleen concanavalin A (Con A)-conditioned medium (SCM) or recombinant IL-2 (but not recombinant IL-1) was able to reverse only about half of the inhibition, as measured along the linear part of the dose-response curve. Inhibition of IL-2 production was lost if a maximally inhibitory dose of cyclosporin was added to the cultures later than 8 hr after antigen stimulation, while proliferation was still suppressed to 50% by cyclosporin added as late as 12 hr and could not be restored by addition of SCM. Both cyclosporins at concentrations that blocked proliferation and IL-2 production significantly suppressed the generation of high-affinity and low-affinity IL-2 receptors by ThS in response to antigen (as assayed by direct binding of 125I-IL-2). These results suggest that CsA and CsG inhibit antigen-induced expansion of ThS by interfering with more than one activation step. In contrast, the in vitro activation of the uveitogenic potential of ThS cells, incubated with antigen in the presence of CsA or CsG and adoptively transferred into untreated recipients, was not affected by the cyclosporins. Thus, triggering of the pathogenic potential of primed autoimmune T-helper lymphocytes can take place in the presence of cyclosporin and in the absence of cellular proliferation.

The Genetics of Obsessive-Compulsive Disorder: An Immunologic Perspective

This article presents a rationale for the hypothesis that an autoimmune mechanism might be involved in the pathogenesis of some forms of obsessive-compulsive aborder (OCO). Existing clinical studies suggesting that some individuals with OCD may have an autoimmune-mediated disorder are briefly summarized. A case example where intravenous immunoglobulin G has been successfully used to treat an adult with OCD spectrum disorder is presented. Preclinical data demonstrating that fragments from the group Αβ hemolytic streptococcus cell wall M proteins can generate antibodies that bind to rat and human tissue are also presented.