Lewis positive

are individuals with active Lewis blood group gene and thus expressing fucosyltransferase‑3. Milk of Le-positive women is rich in α1‑3 and α1‑4 fucosylated human milk oligosaccharide isoforms, such as lacto-N-fucopentaose II and III (Kunz et al. 2017). This gene activity is relevant to define milk groups.