https://ojs.utlib.ee/index.php/SJLAS <p>Published by the Scandinavian Society for Laboratory Animal Science, Sweden</p> <p>Online ISSN <strong>2002-0112</strong></p> Scandinavian Society for Laboratory Animal Science en-US Scandinavian Journal of Laboratory Animal Science 0901-3393 https://ojs.utlib.ee/index.php/SJLAS/article/view/24006 <p>Eosinophilia is a pathological condition characterized by increased eosinophils in tissues and peripheral blood. The type 2 immune response causes eosinophilia, and interleukin-5 (IL-5) secreted by T helper 2 (Th2) cells is essential for increasing eosinophils. However, it is unclear whether there is another mechanism for the increase in eosinophil other than IL-5 upregulation.</p> <p>The present study found high eosinophils in the ICR mice and established inbred mice with hypereosinophilia, named “Yama mouse”, through brother-sister mating.</p> <p>The eosinophils in the peripheral blood of 6-week-old Yama mice were 30-fold higher than those in ICR mice, and Yama mice did not have visible lesions. The IL-5 expression had no significant difference in the spleen, mesenteric lymph nodes, or bone marrow of ICR and Yama mice.</p> <p>Yama mice revealed a mechanism for increased eosinophil counts other than that of IL-5 upregulation. Yama mice exhibit eosinophilia without artificial treatment; therefore, they are a good animal model for studying allergic diseases and regenerative medicine, in which eosinophils are important.</p> Masahiro Morimoto Yusuke Yamada Keisuke Okamoto Saya Kagimoto Masashi Sakurai Yusuke Sakai Moe Hasegawa Hiroyuki Imai Shusaku Shibutani Copyright (c) 2025 Scandinavian Journal of Laboratory Animal Science 2025-04-08 2025-04-08 51 10.23675/sjlas.v51i.24006