Detection of MHC class II expression on human basophils is dependent on antibody specificity but independent of atopic disposition.

A debate has recently arisen as to whether murine basophils can function as antigen presenting cells in allergic inflammation. However, mouse and human basophils differ considerably, and the expression of MHC class II on human basophils has been investigated as a proxy for their capability of antigen presentation but conflicting results have emerged. In this technical note, we show that an antibody specific for all three MHC class II subtypes (HLA-DR, -DP, and -DQ), leads to a significantly higher amount of MHC class II+ basophils compared to antibodies specific for HLA-DR only.

IL-33 induces IL-9 production in human CD4+ T cells and basophils.

IL-33, an IL-1 family member and ligand for the IL-1 receptor-related protein ST2, has been associated with induction of Th2 cytokines such as IL-4, IL-5, and IL-13. Here, we report that IL-33 can initiate IL-9 protein secretion in vitro in human CD4+ T cells and basophils isolated from peripheral blood. TGF-β has been described as a critical factor for IL-9 induction in Th2 cells; however, we found that TGF-β also induces co-production of IL-9 in purified, naïve (>99%) CD4(+)CD45RA(+)CD45RO(-)CD25(-) T cells differentiated towards a Th1 profile.