| CD40 Ligand (CD40L), also known as CD154, TNFSF5, TRAP or gp39, is a 34 39kD type II transmembrane glycoprotein that belongs to the TNF superfamily (1, 2, 3). Human CD40L is 261 amino acids in length and consists of a 22 aa cytoplasmic domain, a 24 aa transmembrane segment, and a 215 aa extracellular region that generates multiple Bstrands and one N-linked glycosylation site (4, 5). Although carbohydrate is present, it is not necessary for activity (6). As with other TNF superfamily members, CD40L will exist as a trimer, both as a membrane bound and soluble form (6, 7, 8). The soluble form is 18kD in size and about 150 aa in length, and arises from intracellular proteolytic processing. As a trimer, the soluble form is bioactive (7, 8, 9). Multiple mutations and alternate splice forms of CD40L exist, often associated with pathology and leading to truncated or nontrimerizable forms of CD40L (8). While CD40L is a ligand for CD40, its ligation also initiates signal transduction in CD40L expressing cells (10). The extracellular region of human CD40L is 99%, 88%, 86%, 82%, 75% and 75% aa identical to the extracellular regions of CD40L in rhesus monkey, cow, pig, dog, mouse and rat, respectively. CD40L binds to both CD40 and to aIIbB3 (3, 11). In the cell membrane, it also associates with a unique splice variant of CD28 (CD28i) that may facilitate CD40L signal transduction (12). Source: Recombinant corresponding to human CD40 expressed in Human embryonic kidney cell, HEK293EBNA. Molecular Weight: ~21.6kD Biological Activity: Measured in a cell proliferation assay using enriched human B cells in the presence of IL-4. Spriggs, M.K. et al. (1992) J. Exp. Med. 176:1543. The ED50 for this effect is typically 0.2-1.2 ng/mL in the presence of 20 ng/mL of recombinant human IL-4 (Catalog 204-IL) and a cross-linking antibody mouse anti-HA. Endotoxin Level: <1EU/ug (LAL method) Storage and Stability: Lyophilized powder may be stored at -20C. Stable for 12 months at -20C. Reconstitute with sterile buffer. Aliquot to avoid repeated freezing and thawing. Store at -20C. Reconstituted product is stable for 6 months at -20C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer. |
