Generation and characterization of mouse basophils from bone marrow and purification of basophils from spleen.

Basophils are rare circulating granulocytes that originate from progenitor cells in the bone marrow and have been considered important effector cells in IgE-mediated allergic inflammation. Basophils constitute <1% of blood leukocytes and are usually absent or present only in small numbers in tissues. They may, however, be recruited to inflammatory sites when an antigen is present and contribute immediately to hypersensitivity reactions. Basophils can therefore serve as primary effector cells in allergic disorders. Despite a large pool of experimental evidence that has led to the discovery of these functional attributes of basophils, many questions regarding their contribution to these immune responses remain unanswered. This is due, in part, to the lack of methods for generation and purification of basophils and the lack of animal models appropriate for their functional analysis. Recent studies, however, have revealed a role for basophils as antigen-presenting cells that preferentially induce Th2 cells in response to complexes of antigen plus antigen-specific IgE, to protease allergens, or to helminth parasites in vitro and in vivo through the production of "early IL-4" and the presentation to CD4(+) T cells of complexes of peptide plus MHC class II molecules. These findings have uncovered previously unknown functional characteristics of basophils. Knowledge of these and other functional properties of basophils may translate into the design of novel therapeutic strategies for Th2-IgE-mediated diseases, such as bronchial asthma. In this unit, protocols that will enable the study of mouse basophils are described.