The present invention relates to a novel epitope to convert T cell to type 17 helper T (TH17) cell. Specifically, the present invention relates to an epitope constituting the 41st to 50th amino acids (SEQ ID No.2) of extracellular domain (ECD) of activation-inducible tumor necrosis factor receptor (AITR), an antibody recognizing the epitope, a polynucleotide encoding the epitope, a polynucleotide encoding the antibody, an expression vector comprising the polynucleotide encoding the epitope or antibody, a transformant introduced with the vector, a composition comprising the antibody for converting T cell to TH17 cell and a method of conversion for the same, a pharmaceutical composition comprising the antibody for preventing or treating infectious disease, a method for treating infectious disease using the antibody, a composition comprising the antibody for enhancing immunity, and a method for enhancing immunity using the antibody.
