VBS++ is like the traditional buffer used in complement assays (GVB++) but it lacks the carrier protein gelatin often used in these assays. GVB may be replaced with VBS
if gelatin is undesirable or may interfere with the assays. The concentrations of metal ions are the traditional concentrations and these give maximal complement activation.
https://www.creative-biolabs.com/complement-therapeutics/vbs-with-ca-and-mg-buffer-2489.htm