Purpose of review: Mechanisms involved in the development of in-vivo type 2 immunity are poorly defined. Basophils are potent IL-4-producing cells and may contribute to the process of polarizing immune responses.
Recent findings: Although basophils represent fewer than 0.5% of blood leukocytes, their frequency dramatically increases under certain circumstances, particularly Th2-related responses including parasitic infection and allergic inflammation. Recent studies proposed the hypothesis that basophils could contribute to the development of type 2 immunity by providing initial IL-4 important in T cell polarization and by recruiting other effector cells such as eosinophils or neutrophils. Multiple stimuli of IgE-dependent and IgE-independent pathways that lead to release of cytokines and mediators from activated basophils have been identified. In addition, progenitors that differentiate into mature basophils have recently been identified.
Summary: The current review revisits basophils with the goal of providing insights into understanding unappreciated roles of basophils in vivo.