Description: 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. (www.uniprot.org) Produced in E.coli. Single, non-glycosylated polypeptide chain, 126 amino acids. The ED50 as determined by the dose-dependant prolifiration of Con A activated rat spleen cells is < 1.5 ng/ml.