A material which is used to verify the performance of an assay intended to be used for the qualitative and/or quantitative detection of interferon gamma (IFN gamma) released in response to T-cell activation resulting from stimulation by one or multiple specific antigens or mitogens, including (but not limited to) B Borrelia species, Epstein-Barr virus (EBV), Cytomegalovirus (CMV), BK virus, severe acute respiratory syndrome-associated coronavirus 2 (SARS-CoV-2), and/or Mycobacterium species.