Figure 1

HLA class-I expression by MCC tumors in situ and MCC cell lines in vitro. (A,B) 56 MCC tumor samples of 40 patients were analyzed by immunohistochemistry for the expression of HLA-A. Samples were scored from 0 to 3 for staining intensity and from 0 to 4 for the frequency of positive tumor cells; a combined HLA-A expression score was calculated by multiplying both scores. One representative tumor for each HLA score group (negative, low, intermediate and high) is depicted in (A); Arrows indicate stromal cells as an internal positive control; scale bar represents 100 µm. (C,D) Four MCPyV⁺ MCC cell lines were analyzed for their HLA class-I expression in vitro. (C) HLA class-I surface expression was detected by flow cytometry using an HLA-ABC detecting antibody (clone W6/32, blue line); matched isotype controls are depicted as grey filled histogram. One representative histogram of triplicates is shown for each cell line. (D) The cellular localization of HLA class-I was determined by immune fluorescence using wheat germ agglutinin (Alexa fluor 647, red) as membrane marker and a HLA-A detecting antibody (clone EP1395Y) with a dylight 488 labeled secondary antibody (green). Representative images for each cell line were captured with a confocal microscope; scale bars represent 10 µm.