Residential Area, Birth Order, and Dietary Habit May Influence TSLP Levels in Colostrum: Comparative Study between Japan and Nepal

Thymic stromal lymphopoietin (TSLP) is an IL-7-like cytokine that is produced mainly by epithelial cells. TSLP was originally identified as a factor derived from a thymic stromal cell line that could support the growth of a mouse B cell line. However, recent studies in mice and humans establish TSLP as a "master switch" for allergic inflammation. Interestingly, Macfarlane et al. reported that TSLP was present in human milk. However, it remains unclear what maternal environmental and intrinsic factors, as well as parturition characteristics, affect TSLP levels in human milk. This study therefore aimed to identify such factors influencing TSLP levels in human milk by epidemiological analysis. For this purpose, we obtained colostrum samples from lactating women living in Japan, a developed Asian country with good sanitation facilities, and Nepal, a developing Asian country with limited sanitation. Both countries also differ in cultural and economic factors as well as dietary habits. Breast milk samples were collected from lactating women admitted in hospitals in Yamanashi prefecture, Japan, and in hospitals in Kathmandu district and Kavrepalanchok district, Nepal and were stored at-20℃ until the analysis.