Table 2.

Colony formation by single YS-HSCs (day 10) following coculture with irradiated C166 YS-ECs

Colony size (no. of cells per well)	Number of colony-positive wells		Total no. of colonies
	Mixed	Unmixed
<5,000	0	21	21
5,000–10,000	5	29	34
>10,000	2	19	21
Total no. (%)	7 (9%)	69 (91%)	76
Positive wells, %	3.5	34.9	38.4

Single cell sorting of WGA⁺ cells (brightest, 25%) was carried out on AA4.1⁺, low-density, nonadherent cells isolated from freshly dissected yolk sacs (10-day embryos). A total of 198 wells were first seeded with C166 YS-ECs, which were permitted to grow to confluence and were then irradiated (25 Gy). Cultures were assayed following 8 days of coculture.