VBS o is like the traditional buffer used in complement assays (GVB o ) 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. Ca ++ and Mg ++ may be added to VBS o to make VBS ++ for classical pathway and lectin pathway assays. MgEGTA may be added to VBS o for alternative pathway assays. EDTA may be added to VBS o to prepare VBSE to inhibit complement activation. VBS o is also used for dilution of serum and other assay components in many complement assays especially in alternative pathway assays (Morgan, B.P. (2000; Dodds, A.W. and Sim, R.B. (1997)).