Landsteiner discovered the P1 antigen in 1927. Anti-P1 does not generally react above room temperature and may often go undetected in routine testing. Anti-P1 does not cause Haemolytic Disease of the Newborn and has only rarely been associated with Haemolytic Transfusion Reactions.

The reagent will cause agglutination (clumping) of test red cells, that carry the P1 antigen, after centrifugation. No agglutination generally indicates the absence of the P1 antigen.

Lorne Monoclonal IgM Anti-P1 blood grouping reagent contains murine monoclonal IgM antibodies prepared from the cell line, Clone 650, diluted in a solution containing sodium chloride and bovine albumin.