Elucidating the Inhibitory Mechanism of Müller Cells on T Lymphocyte Proliferation in vitro

Abstract

Purpose: : To examine the ability of murine Müller cells (MC) to inhibit activation and proliferation of T lymphocytes and identify the molecule(s) by which this effect occurs.

Methods: : MC from primary cultures established from wild type (WT) or genetically manipulated C57BL/6 mice were irradiated and co-cultured with sorted CD4+ T cells stimulated with anti CD3/CD28. Blocking Abs and supernatant transfers were used to study the surface molecule(s) involved in inhibition and its contact dependence. Regulatory phenotype and function of T cells retrieved from T/MC co-cultures were examined by expression of FoxP3 and CD25 and inhibition of naive stimulated T cells, respectively. Proliferation of T cells was measured by 3H-thymidine incorporation or by dilution of CFSE.

Results: : Murine MC strongly inhibited CD3/CD28 driven T cell proliferation in a contact dependent fashion. The use of TSP-1-/-, B7.1-/- and mice deficient in TGF-β signaling, as well as blocking antibodies to B7.1, TGF-β and TSP-1 revealed that interference with these molecules diminished, but did not completely abrogate the inhibitory effect. CD25 expression was inhibited and FoxP3 expression was not induced in CD4+ T cells by co- culture with MC. Regulatory function that could be attributed to an effect of MC was also not demonstrable.

Keywords: Muller cells • immunomodulation/immunoregulation • inhibitory receptors