Table 1.

Capacity of transfected Drosophila cells to stimulate primary proliferative responses and IL-2 production by CD8⁺ 2C lymph node cells

Assay	Peptides added	[3H]Thymidine incorporation (cpm × 103) with transfected Drosophila cells expressing
		Ld	Ld.B7	Ld.ICAM	Ld.B7.ICAM	Ld.B7 + Ld.ICAM*
Proliferation	—	0.2*	0.1	0.3	0.2	—
(day 3)	p2Ca	0.2	0.3	1.5	142.0	1.5
	QL9	0.3	60.9	73.9	263.7	132.9
IL-2 production	—	0.3	0.2	0.1	1.2	—
(day 2)	p2Ca	0.2	0.2	0.1	64.6	0.3
	QL9	0.1	0.4	0.2	158.6	0.5

Doses of 5 × 10⁴ highly-purified naive-phenotype CD8⁺ 2C lymph node cells were cultured at 37°C with 3 × 10⁵ transfected Drosophila cells ± peptides (10 μM final concentration) in 0.2 ml in 96-well plates (25). Proliferative responses were measured by adding [³H]thymidine (³HTdR) (1 μCi/well) 8 hr before harvest. IL-2 production was measured by removing supernatants from the cultures at 48 hr and adding 50 μl supernatant to the IL-2-responsive indicator line, CTLL (25). Proliferation of the indicator line was measured by addition of [³H]thymidine. It should be noted that Drosophila cells die rapidly at 37°C and fail to incorporate [³H]thymidine at this temperature. Data are given as the mean of triplicate cultures; SD were generally within 5–15% of the mean. 

^*Values are 1.5 × 10⁵ of each population.