Poster Presentation The 13th International Congress of the Immunology of Diabetes Society 2013

Soluble CD52 suppresses innate immune responses and is a candidate therapeutic agent in type 1 diabetes (#110)

Maryam Rashidi 1 , James E. Vince , Yuxia Zhang , Esther Bandala-Sanchez , John M. Wentworth , Leonard C. Harrison
  1. Walter & Eliza Hall Institute of Medical Research, Melbourne, Vic, Australia

Background & Aim: We have recently shown that T cells with high expression of CD52 suppress other T cells via the release of soluble CD52, which binds to the inhibitory receptor, Siglec 10 (1). Innate immune activation is a prerequisite for adaptive immune-mediated destruction of pancreatic beta cells in type 1 diabetes. We aimed to determine if CD52-Fc could suppress innate immune function, to further support its therapeutic application in type 1 diabetes.

Methods: CD52-Fc or control Fc protein was purified from medium of transfected 293T cells by Protein A affinity chromatography under low endotoxin conditions. THP-1 cells, primary human monocytes, mouse bone marrow-derived macrophages (BMDM) or dendritic cells (BMDC) (2x105) were cultured in 96-well round-bottom plates with different concen­trations of recombinant protein in presence of LPS or other TLR ligands for 24 h at 37° C. Medium was collected for measurement of cytokines by ELISA. THP-1 cells expressing GFP as an NF-kB reporter were also used as a read-out.

Results: CD52-Fc, but not Fc, markedly suppressed IL-1β, TNF-a and IL-6 production by human monocytes, BMDMs and BMDCs in response to LPS and other innate immune stimuli, by inhibiting NF-kB signaling. Treatment of CD52-Fc with the endoglycosidase PNGase F to remove N-linked oligosaccharide or treatment with neuraminidase to remove terminal sialic acids abolished its suppressive effect. Accordingly, we showed that CD52-Fc interacts with the lectin receptor Siglec 10 on human monocytes and with Siglec E on BMDMs. Studies in progress will determine the therapeutic efficacy of CD52-Fc in the prevention of type 1 diabetes in the NOD mouse.

 Conclusion: In addition to suppressing T-cell function, CD52-Fc suppresses innate immune cell function. This re-inforces the therapeutic potential of CD52-Fc in immuno-inflammatory diseases such as type 1 diabetes.