Reprogramming immune proteins as therapeutics using molecular engineering

•Molecular engineering is reshaping immunotherapeutic discovery, design, and development.•Cytokines can be engineered to improve their stability, affinity, and specificity.•Anti-cytokine antibodies can bias cytokine activities for targeted disease therapy.•Elucidating antibody mechanisms of action informs their engineering and optimization.•Molecular insights will empower design of synergistic combination therapy strategies.