From an examination of the skin lesions, quantitated by an exudates-absorbed method, around the air pouches, we found that all ST2-KO mice showed skin lesions within 2 days after infection and the lesion areas were 85 ± 28 mm2 (n = 6); these lesion areas were larger than those of IL-33-KO mice (58 ± 5 mm2; n = 6, p < 0.01) and WT mice (29 ± 15 mm2; n = 6, p < 0.01) after GAS infection. This evidence concerns the gene IL33 and infection.