Abstract
Purpose: :
Previously, we have demonstrated that SOCS proteins modulate the differentiation of naïve CD4+ T cell into Th1 or Th2 effector cells. Here, we have examined whether SOCS proteins play a role in regulating trafficking of newly differentiating CD4+ Th cells into peripheral tissues.
Methods: :
SOCS1–/–, STAT1–/– double knockout (DKO) mice were generated by crossbreeding SOCS+/– and STAT1–/– mutant mice. DKO mice were identified by tail DNA PCR genotyping, Real–time PCR, and Western Blotting. Immunophenotype of the DKO mice was characterized by FACS analysis of their PBMC. Mature Th cells with either over–expression or targeted deletion of SOCS1 or SOCS3 were generated by retroviral–mediated transduction of SOCS1, SOCS3, SOCS1–antisense or SOCS3–antisense cDNA construct. Analysis of chemokine, chemokine receptors, and SOCS and STAT expression was by Ribonuclease Protection Assay (RPA), Western blotting or FACS analysis. Lymphocyte chemotaxis was performed by the standard 2–chamber Transwell migration assay.
Results: :
We show that surface expression of CCR7 is dramatically decreased in peripheral CD4+ cells of SOCS+/–/STAT1 heterozygous or SOCS1/STAT1 DKO mice and the decrease in CCR7 expression is accompanied by increased expression of the CD44 lymphocyte activation marker and down–regulation of CD45RB or CD62L, indicating a marked elevation of the number of memory–like Th cell phenotypes in these mice. We further show that over–expression of SOCS1 induces CCR7 expression and enhances migration of CCR7–expressing cells to their cognate ligand, ELC (CCL19)/SLC (CCL21). In addition, SOCS1/STAT1 DKO mice have severe inflammation of the skin and/or eyes.
Conclusions: :
Our in vivo and in vitro studies indicate that SOCS1 up–regulates expression of CCR7, a receptor that plays critical roles in retaining lymphoid cells in secondary lymphoid organs. In addition, morphological and histological analyses of the SOCS1–deficient mice reveal multi–organ infiltration of inflammatory cells, as suggested by severe inflammation of the skin and/or eyes of these mice. Thus, these results suggest that SOCS proteins may play important roles in immune homeostasis by regulating the activation and migration capacity of inflammatory cells.
Keywords: cytokines/chemokines • immunomodulation/immunoregulation • inflammation