How is the Fc region of antibodies engineered to modify effector functions?

Fc engineering modifies antibody effector functions for therapeutic purposes. Strategies include: 1) Enhanced ADCC - mutations increasing FcgammaRIIIa binding (S239D/I332E, afucosylation through glycoengineering); obinutuzumab for CLL. 2) Enhanced CDC - mutations increasing C1q binding (K326W/E333S). 3) Silenced effector functions - for blocking/neutralizing antibodies where cytotoxicity is undesired; mutations L234A/L235A/P329G (LALA-PG). 4) Extended half-life - YTE mutations (M252Y/S254T/T256E) increase FcRn binding at pH 6, extending half-life 2-4 fold. 5) Bispecific formats - knobs-into-holes, CrossMab, DuoBody enable heterodimeric Fc pairing. 6) Fc fusion proteins - attach Fc to extend half-life of peptides/proteins (etanercept). These modifications enable optimization for specific therapeutic applications.