Provided herein are recombinant antibodies, antigen-binding fragments, and fusion proteins thereof useful for binding to and inhibiting programmed death 1 (PD-1), nucleic acid molecules encoding the same and therapeutic compositions thereof, as well as methods of using such antibodies, including the methods for enhancing T cell and NK cell function to increase cell and cytokine mediated immunity and methods of treatment of various immune dysfunction related disorders including cancer and infectious diseases.