Person:

Masli, Sharmila

Purpose: Anterior chamber associated immune deviation (ACAID) is an antigen-specific form of peripheral immune tolerance that is induced to exogenous antigens placed in the ocular anterior chamber, which leads to a suppression in delayed-type hypersensitivity (DTH). Considerable work has been done on ACAID induction to major histocompatibility (MHC) alloantigens. However, its role on cytotoxic T lymphocyte (CTL) activity is currently unknown. Methods: C57BL/6 (H-2b) mice received an intracameral (IC) inoculation with BALB/c (H-2d) splenocytes. Splenic CD4+ and CD8+ T cell populations were characterized by flow cytometry and proliferation assays during induction and expression phases of ACAID. Percentages of CD4+CD25+FoxP3+ T regulatory cells (Treg) were also followed. Lastly, CTL function was measured at various time points during ACAID expression, and Treg were added to identify potential alterations in CTL function. Results: CD4+ and CD8+ T cell percentages and proliferation increased in the spleen during ACAID induction but then sharply decreased in response to an allospecific immunization. Expression of ACAID also exhibited a significant drop in CTL function. However, while Treg expansion was observed, these cells did not directly mediate the CTL inhibition. Conclusions: ACAID mediates an inhibition of CTL function against MHC alloantigens. Furthermore, we found that ACAID induction leads to the expansion and proliferation of CD4+ and CD8+ T cells while ACAID expression is associated with a diminishment in T cell percentages due to proliferation impairment. Lastly, Treg also expand during ACAID induction. However, our data suggest that Treg do not directly inhibit CTL activity.

Background: The Gpnmb gene encodes a transmembrane protein whose function(s) remain largely unknown. Here, we assess if a mutant allele of Gpnmb confers susceptibility to glaucoma by altering immune functions. DBA/2J mice have a mutant Gpnmb gene and they develop a form of glaucoma preceded by a pigment dispersing iris disease and abnormalities of the immunosuppressive ocular microenvironment. Results: We find that the Gpnmb genotype of bone-marrow derived cell lineages significantly influences the iris disease and the elevation of intraocular pressure. GPNMB localizes to multiple cell types, including pigment producing cells, bone marrow derived F4/80 positive antigen-presenting cells (APCs) of the iris and dendritic cells. We show that APCs of DBA/2J mice fail to induce antigen induced immune deviation (a form of tolerance) when treated with TGFβ2. This demonstrates that some of the immune abnormalities previously identified in DBA/2J mice result from intrinsic defects in APCs. However, the tested APC defects are not dependent on a mutant Gpnmb gene. Finally, we show that the Gpnmb mediated iris disease does not require elevated IL18 or mature B or T lymphocytes. Conclusion: These results establish a role for Gpnmb in bone marrow derived lineages. They suggest that affects of Gpnmb on innate immunity influence susceptibility to glaucoma in DBA/2J mice.