Table II.

Ab blocking of T cell response

		T Cell Line
Stimulator	Blocking Aba	C6	C7 IFN-γ (pg/ml)	C7-5	G209b
Tumor cellsc	None	500	800	1600	838
Tumor cells	Anti-DR	9 (98)d	240 (70)	320 (80)	924 (0)
Tumor cells	Anti-class II	159 (68)	480 (40)	890 (44)	711 (15)
Tumor cells	Anti-class I	534 (0)	990 (0)	1800 (0)	<8 (>99)
None	None	<8	<8	<8	<8

^aThe 1290 mel tumor cell line (2 × 10⁴ cells/well) that was treated with 500 U/ml of IFN-γ was incubated with either an Ab directed against HLA class I (W6/32), HLA class II (IVA12), or HLA-DR molecules (HB55) for 2 h prior to incubation with the indicated T cells (2 × 10⁴ cells/well). Targets were incubated with T cells for 18–24 h, and the release of IFN-γ was measured in an ELISA.

^bG209 is a T cell clone that recognizes the Gp100:209–217 T cell epitope in the context of the HLA-A2 class I allele.

^cThe C6, C7, and C7-5 cells were stimulated with 1290 mel cells that were treated for 72 h with 1000 U/ml of IFN-γ. The G209 T cells were stimulated with the HLA-A2-expressing 1300 mel cell line.

^dThe numbers in parentheses indicate the percent inhibition of the cytokine release observed in the presence of the indicated Abs.