Purity ~98% by SDS-PAGE and HPLC. Endotoxin: ≤ 0.1ng/ug (1EU/ug). Recombinant human soluble CD40 ligand is a 16.3kD protein containing 149aa residues comprising the receptor binding TNF-like domain of CD40L. CD40 is a member of the TNF receptor family. it is a cell surface protein expressed on B cells, dendritic cells, monocytes, thymic epithelial cells and, at low levels, on T cells. Signaling though CD40 plays an important role in the proliferation and differentiation of B cells, and is critical for immunoglobulin (Ig) class switching. The membrane-anchored CD40-Ligand is expressed almost exclusively on activated CD4+ T lymphocytes. Failure to express CD40L leads to ?immunodeficiency with hyper-IgM, a disease characterized by failure to produce IgG, IgA and IgE. The human CD40L gene codes for a 261aa type II transmembrane protein, which contains a 22aa cytoplasmic domain, a 24aa transmembrane domain and a 215aa extracellular domain. The soluble form of CD40L is an 18kD protein compri