ICOS and triple-A syndrome: Due to the surface marker complexity, it is technically difficult to use immunostaining, immunoblot, or ELISA to detect or quantify these cells or their molecules in human AAA lesions, although ICOS+GATA3+, ICOS+, or IL17RB+ cells have been considered tissue ILC2.[26, 58, 59] Although it is also technically impractical to isolate ILC2 from human AAA lesions, study of human ILC2 in fresh blood donors from AAA patients is possible and may provide important information whether blood ILC2 contents correlate with AAA lesion size or growth rate.