Abstract: The receptor killer cell lectin-like receptor G1 (KLRG1) is expressed on T and NK cells, which binds to ligands on epithelial and mesenchymal cells. The ligand for KLRG1 has been described to be E-cadherin, N-cadherin, and R-cadherin. The present disclosure relates to and results from the discovery and characterization of antibodies that bind the extracellular domain (ECD) of KLRG1 but do not interfere with its interaction with the ligands E-cadherin, N-cadherin, and R-cadherin. The antibodies described have been derived by mouse hybridoma technology, and can be humanized by grafting their complementary determining regions (CDRs) into a human framework. The antibodies described can be used as effective therapeutic agents. Various antibodies, or antigen-binding fragments of such antibodies, along with various therapeutic and/or diagnostic methods, among other features, are provided for in the present disclosure.