Disclosed is the use of a synthetic antigen-lipid construct of the structure F-S1-S2-L in the manufacture of a preparation for neutralising one or more populations of circulating antibody in a subject mammal wherein: -F is the epitope of a carbohydrate antigen (glycotope) reactive with the one or more populations of circulating antibody -S1-S2 is a spacer linking F to L selected to provide an antigen-lipid construct that is dispersible in water and preferentially partitions into plasma relative to naturally occurring glycolipids and -L is a di-acyl or di-alkyl glycerophospholipid. Further disclosed is the use where the preparation is a medicament for administration to a human prior to transfusion or transplantation to mitigate the risk of a clinically significant reaction to a donor antigen.
