Study On The Role Of MICA-expanded Vδ1 γδ T Cell Receptors

Human MHC class I chain-related A (MICA) is a nonclassic HLA I ploymorphic gene. MICA and its close relative MICB are members of MIC gene family, which are located in the MHC locus. MICA is a highly glycosylated, single-chain transmember proteins. Its characteristics include the lack of association with β2-microglobulin (β2M), stable expression without conventional class I peptide ligands, and the absence of a CD8 binding site. MICA is a stress-inducible and tumor-associated antigen, which can be expressed on many kinds of epithelial tumors and can be recognized by the human Vδ1 γδ T cells.The human Vδ1 γδ T cells are the major element of intestinal epithelial lymphocytes (IELs), and the first line of defense system. Vδ1 γδ T cells have been proved to be responsive to MHC class I-related (MIC) A and B, through the two kinds of receptors, NKG2D and Vδ1 γδ TCR. Upon heat shock and other stresses, expression of MICA/B is up-regulated and thus trigger the cytotoxic reaction of Vδ1 γδ T cells. However, it is still unclear about how the Vδ1 γδ T cells recognize MICA~+ cells. A dual-signal theory was given to explain this reaction and the theory needs more data to support. Our works give some support to this dual-signal theory through the analysis of γδ TCR engagement and cytolysis assay of Vδ1 γδ T cells to MICA~+ tumor cell line.In the early works, the total RNA was obtained from SKOV3 ovary tumor cells and whole length cDNA of MICA was amplified by RT-PCR. The recombinant MICA (rMICA)*008 contain α1-α3 domains was expressed in prokaryocyte and purified successfully. And we previously reported that immobilized recombinant MICA could induce the proliferation of human ovarian epithelia carcinoma-deriving γδ T cell of the Vδ1 phenotype in vitro, and the cytolytic activity towards tumor cell...