ABO and malaria: Previous genetic studies in Brazilian Amazonian populations have demonstrated different malaria protective effects from blood-related polymorphisms (e.g. Duffy, ABO, Rh, MNSs and Kell systems [17], [18], [19], [20]), erythrocyte enzymes (G6PD [18]), receptors (CR-1, complement receptor 1) [20], [21], and polymorphisms which play a critical role in the early innate immune response to invading pathogens (e.g. TLRs [20], [22]).