A “LALA” mutation within the Fc region of SIgN-3C, by substitution from leucine to alanine at positions 234 and 235 (L234A/L235A), abrogated binding to FcγR and severely reduced infection enhancement in K562 cells, indicating that the SIgN-3C LALA mutant prevented ADE. The gene discussed is FCGR2A; the disease is infection.