Loss of the interferon-γ-inducible regulatory immunity-related GTPase (IRG), Irgm1, causes activation of effector IRG proteins on lysosomes, damaging lysosomal function and predicting the dramatic susceptibility of Irgm1-deficient mice to infection

Table 1 Cooperativity and hierarchy of IRG loading to lysosomes^a

IRGs	Experiment	Total lysosomes	Lys. without IRGs	Lys. with 1^st IRG only	Lys. with 2^nd IRG only	Lys. with 1^st and 2^nd IRG	P value^b	Independent or cooperative
Irga6 + Irgb6	1	1090	713	305	4	68	<0.0001	Cooperative
Irga6 + Irgb6	2	1477	768	536	14	159	<0.0001	Cooperative
Irga6 + Irgd	1	1692	880	503	18	291	<0.0001	Cooperative
Irga6 + Irgd	2	1232	702	299	8	223	<0.0001	Cooperative
Irga6 + Irgb10	1	899	437	257	123	82	0.7995	Independent
Irga6 + Irgb10	2	1337	570	459	184	124	0.5973	Independent
Irgb10 + Irgb6	1	1060	866	144	2	48	<0.0001	Cooperative

^aLysosomes carrying or not carrying IRG proteins were identified microscopically by co-staining with antibodies against LAMP1 and different pairs of IRG proteins
^b P values were calculated in a χ² analysis with 3 d.f. of the four categories of lysosome, based on expectation of random assortment of the two IRG proteins

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