Activation of the Lectin Pathway The soluble plasma protein,Mannan-Binding Protein(MBP or MBL)binds to the sugar mannan which is restricted to the surface of certain microbes (not on vertebrate cells) This leads to attachment of other complement proteins (C4,C2)to form the C3 convertase of the Lectin Pathway.Activation of the Lectin Pathway The soluble plasma protein, Mannan-Binding Protein (MBP or MBL) binds to the sugar mannan which is restricted to the surface of certain microbes (not on vertebrate cells) This leads to attachment of other complement proteins (C4,C2) to form the C3 convertase of the Lectin Pathway