Abstract
Purpose: :
To investigate the mechanism(s) of intravenously (i.v.) induced immune tolerance to experimental autoimmune anterior uveitis (EAAU) causing antigen in sensitized Lewis rats.
Methods: :
EAAU was induced in Lewis rats by foot-pad injection of melanin associated antigen (MAA) emulsified with complete Freund’s adjuvant. Tolerance was induced in these pre-sensitized animals by i.v. administration of different amounts of MAA at days 6, 7, 8 and 9 post-immunization. Animals were sacrificed at the onset of EAAU and mixed lymphocytes harvested from the popliteal lymph nodes were cultured in the presence or absence of MAA. Mixed lymphocytes were stained with anti-CD4, anti-CD8, anti-CD25, anti-FoxP3 and CFSE (for cell proliferation assay) for flow cytometry. Annexin V and apopstat staining (for flow cytometric analysis) along with TUNNEL (for immunofluorescent staining of paraffin sections) was utilized to detect the apoptosis of lymph node cells.
Results: :
Intravenous administration of MAA (400, 600 and 800 µg) on days 6, 7, 8 and 9 post-immunization induced tolerance and inhibited EAAU in all Lewis rats. Flow cytometric analysis revealed that the proliferation of total lymphocytes, CD4+T cells and CD8+ T cells harvested from the popliteal lymph nodes in response to antigenic stimulation was drastically reduced in the state of tolerance compared to the cells from non-tolerized animals. Flow cytometric analysis demonstrated that the number of CD4+CD25+FoxP3+ Tregs increased in the popliteal lymph nodes of tolerized animals compared to non-tolerized animals. Results of immunofluorescent staining and flow cytometric analysis revealed increased number of apoptotic cells (total T cells, CD4+ T cells and CD8+ T cells) in the popliteal lymph nodes of the tolerized animals compared to non-tolerized animals.
Keywords: immune tolerance/privilege • immunomodulation/immunoregulation • inflammation