In addition, low numbers of peptide/MHC II tetramer-positive cells have been reported in recent studies on the detection of CD4+ T cells in response to infectious agents, autoantigens, allergens and tumour antigens, with frequencies generally ranging from 0.02 to 0.6% of the total number of CD4+ T cells [47]–[54]. This evidence concerns the gene CD4 and neoplasm.