Structural domains that comprise this superfamily share the structure of the a pro-allergic, IL-7-like hematopoietic, cytokine thymic stromal lymphopoietin (TSLP), key in the development of widespread chronic inflammatory disorders such as asthma and atopic dermatitis. This domain is annotated on InterPro to mainly function on myeloid cells, causing their proliferation and may promote inflammatory responses by directly activating mast cells.