Another recent prospective proof-of-concept study uses a novel T-cell activation marker-tuberculosis (i.e., TAM-TB) assay on cryopreserved peripheral blood mononuclear cell samples to diagnose active TB in children based on ratios of CD27 phenotype of CD4 T cells producing IFNγ in response to Mtb antigens (i.e., ESAT6 and CFP10) [42]. Here, CD4 is linked to tuberculosis.