Silencing S1P1 receptors regulates collagen-V reactive lymphocyte-mediated immunobiology in the transplanted lung

Abstract

Type V collagen (col[V])-reactive lymphocytes contribute to lung transplant rejection, but the mechanisms for emigration into the graft are unknown. Sphingosine-1-phosphate-1 receptors (S1P1R) are believed to be required for lymphocyte emigration in other studies, but their role in col(V)-reactive lymphocyte rejection responses is not known. Utilizing small interfering RNA (siRNA) to reduce S1P1R expression on col(V)-reactive lymphocytes, we examined the role of S1P1R in the rejection response. Quantitative polymerase chain reaction (PCR) revealed strong expression of S1P1R messenger RNA (mRNA) on col(V)-reactive lymphocytes isolated from immunized rats. S1P1R-specific siRNA (S1P1R siRNA) reduced expression of S1P1R mRNA and protein, whereas scramble siRNA (SC siRNA) had no effect. Adoptive transfer of lymphocytes treated with S1P1R siRNA to rat Wistar Kyoto (WKY) lung isograft recipients resulted in retention of cells within the liver with fewer cells in mediastinal lymph nodes when compared to cells exposed to SC siRNA. S1P1R-deficient cells proliferated in response to alloantigens, but not in response to col(V), and produced less interferon (IFN)-γ in response to col(V) compared to controls. Downregulating S1P1R did not affect production of interleukin (IL)-10 and tumor necrosis factor (TNF)-α, or expression of adhesion molecules critical for migration, but prevented rejection pathology and lowered local levels of IFN-γ post adoptive transfer. These data demonstrate novel roles of S1P1R, which include regulating emigration and modulating lymphocyte activation. © 2008 The Authors.