CR1 and malaria: CR1 is involved in clearance of C3b/C4b-coated immune complexes and regulation of complement activation, and RBCs with low CR1 may be more susceptible to complement-mediated damage and increased clearance, which are mechanisms associated with severe malarial anaemia.29, 47, 48 Alternatively, Sl2 and McCb could be under selection through other diseases unrelated to malaria.