Retnlb, also known as resistin-like molecule beta (RELMbeta), is a bioactive molecule synthesized by intestinal goblet cells [1]. It is involved in various biological processes such as host defense and immune regulation. In the context of intestinal health, it may contribute to the function of the mucus layer, an important part of the innate host defense [1].

In functional studies, gene knockout mouse models have been used to understand the role of Retnlb. For example, in hookworm infection, Retnlb(-/-) mice exhibited high parasite egg burdens, suggesting that Retnlb can promote worm expulsion [2]. In allergic asthma, Retnlb -/- mice had greater chronic disease markers like goblet cell numbers and airway wall remodelling, indicating that Retnlb may reduce the development of chronic features of allergic airways disease [4]. In colorectal cancer, a significant reduction of Retnlb expression was found in CRC biopsies compared to healthy mucosa, and low levels were associated with an unfavorable prognosis [3].

In conclusion, Retnlb plays essential roles in host defense, especially in worm expulsion during hookworm infection and in modulating the development of chronic features in allergic asthma. In colorectal cancer, its reduced expression is linked to poor prognosis. The use of Retnlb knockout mouse models has been crucial in revealing these functions in these specific disease areas.