Purity > 90% as determined by SDS-PAGE. MW: 19kDa. Full Length of Mature Protein: 25-153aa. N-terminal 6xHis-tagged. Homo sapiens (Human). Participates in at least several B-cell activation processes as well as of other cell types. It is a costimulator of DNA-synthesis. It induces the expression of class II MHC molecules on resting B-cells. It enhances both secretion and cell surface expression of IgE and IgG1. It also regulates the expression of the low affinity Fc receptor for IgE (CD23) on both lymphocytes and monocytes.