TABLE 1.

Screening ricin-resistant cell lines

Ricin resistancea	PEx resistancea	Color codeb	No. ricin binding sitesc	No. cell linesd	Candidate loss of function
-Fold	-Fold
18–21	∼1	Green	Very low	3	Loss of ricin receptors
2–9	5–9	Orange	Medium-normal	6	Toxin trafficking, processing, or dislocation
2–13	0.3–3	Gray	Medium-normal (group I)	∼38	Toxin trafficking, processing, or dislocation
2–13	0.3–3	Gray	Low-medium (group II)	∼20	Loss of ricin receptors
6–10	1–2	Violet	Low	3	Loss of ricin receptors; Golgi α-mannosidase II

^a -Fold resistance over parental (IC₅₀ clone: IC₅₀ HEK 293T).

^b Color code is defined in Fig. 1.

^c Determined by flow cytometry after binding Alexa Fluor 647-labeled ricin B chain.

^d Eight cell lines (seven “gray” and one “green”) were not tested for Alexa Fluor 647-labeled ricin B chain binding.