Human CD40L (CD154) is one member of TNF family which is expressed on T cells. It binds the CD40, which is on the antigen-presenting cells (ex: B cells, macrophages and monocytes) Human CD40L is a 21.6 kDa cytokine with 103 amino acid residues which is a transmembrane glycoprotein. Human CD40L plays an important role in the adaptive immune system which induces the B cell maturation and activation.