The present invention provides, as a gene encoding an antigen recognized by a G-CSF inducing antibody, a gene encoding any one of the following proteins: (a) a protein having an amino acid sequence shown in SEQ ID NO; 2; (b) a protein having an amino acid sequence comprising a deletion, substitution, addition or insertion of one or several amino acids with respect to the amino acid sequence shown in SEQ ID NO: 2, and having a binding ability for an antibody which induces and secretes a granulocyte colony-stimulating factor or a fragment thereof: or (c) a protein having at least 50% or more homology with the amino acid sequence shown in SEQ ID NO: 2, and having a binding ability for an antibody capable of inducing and secreting a granulocyte colony-stimulating factor or a fragment thereof.