Figure 5.
(A) Effect of HLA-G expression by IGR melanoma on sensitivity to lysis by the YT2C2-PR subclone. K562 transfected with either the vector alone (K562-pRc/RSV), HLA-G1 (K562-HLA-G1), or HLA-G2 (K562-HLA-G2) and the M8, M74, and IGR melanoma cell lines were used as targets. The YT2C2-PR subclone was used as an effector cell at a 50:1 effector/target (E/T) ratio. Results are expressed as the percentage of specific lysis recorded in a 4-h 51Cr-release assay. Spontaneous release never exceeded 10% of the maximum release. This experiment was repeated at least five times, yielding the same pattern of protection. (B) Inhibition of YT2C2-PR lysis is caused by an “off signal” transmitted by IGR melanoma cells. The M8 melanoma cell line was used for Cr-labeled target cells. The YT2C2-PR subclone was used for effector cells at a 50:1 E/T ratio. The IGR melanoma cell line was added as inhibitor cells at 100, 50, and 25:1 inhibitor/target ratios. Zero indicated that no IGR cells were added to the test.