Expression of the transporter for antigen processing-1 (Tap-1) Gene in subpopulations of human trophoblast cells.
Heterodimers of transporter for antigen processing proteins, Tap-1 and Tap-2, are essential components of the pathway that leads to expression of conventional HLA-A, -B class I transplantation antigens on cell surfaces. In this study, expression of the Tap-1 gene in trophoblast cells, some of which display novel and unconventional HLA class I molecules that include HLA-G and an HLA-C-like antigen, was investigated by using in situ hybridization to identify Tap-1 mRNA and immunohistochemistry to detect Tap-1 protein. The experiments were done on semiserial sections of paraformaldehyde-fixed tissues. In first trimester placentas, expression of the Tap-1 gene correlated with expression of HLA class I antigens in trophoblast cells. HLA-G/C positive extravillous cytotrophoblast cells exhibited high intensity in situ hybridization signals for Tap-1 mRNA and strong staining with anti-Tap-1 whereas Tap-1 gene products were rarely detected in HLA class I antigen negative syncytiotrophoblast and villous cytotrophoblast cells. Relationships were less definitive in term tissues. Although Tap-1 protein was detectable in extravillous cytotrophoblast cells (chorionic cytotrophoblast cells) as expected, HLA class I negative syncytiotrophoblast contained low intensity hybridization and immunostaining signals. Collectively, the data suggest that (1) as with conventional HLA class I antigens in other types of cells, the pathway leading to expression of novel HLA class I antigens in trophoblast cells includes transport of peptides by Tap-1, and that (2) deficiencies in Tap-1 might account in (whole or in) part for the failure of some trophoblast cells to express HLA class I antigens.[1]References
- Expression of the transporter for antigen processing-1 (Tap-1) Gene in subpopulations of human trophoblast cells. Roby, K.F., Gershon, D., Hunt, J.S. Placenta (1996) [Pubmed]
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