A1 antigen is a subgroup of A and was discovered in 1910. Anti-A1 is usually non-reactive at 37ºC, however examples reactive at 37ºC and predominately IgM can cause in vivo red blood cell destruction. About 78% of group A people are A1 and 22% are A2, similar proportions apply among AB people.

The reagent will cause agglutination (clumping) of test red cells, that carry the A1 antigen, after centrifugation. No agglutination generally indicates the absence of the A1 antigen.

Lorne Anti-A1 Lectin blood grouping reagent is prepared from an extract of Dolichos biflorus seeds, diluted with a sodium chloride solution containing bovine albumin. The reagent is supplied at optimal dilution for use with slide & tube techniques.