Lectins are plant extracts that have the ability to agglutinate human red blood cells. Specific lectins are associated with certain red blood cell antigens and can prove to be beneficial when trying to resolve an ABO discrepancy generated by problems arising from ABO antigens (Table 19).
Table 19. Lectins and their Associated Red Blood Cell Antigens.| Lectin | Agglutinates | Purpose |
| Dolichos biflorus | A1 or A1B cells | A subgroup resolution |
| Bandeiraea simplicifolia | B cells | B subgroup or Acquired B resolution |
| Ulex europaeus | O cells and other groups according to the amount of H antigen present | Bombay and ABO subgroup resolution |
