We earlier documented reduced in Bp-specific proliferative responsiveness in ex-pertussis cases, using a 3H thymidine assay and whole PT or single PT and PRN CD4+ T-cell epitopes as antigenic stimulation, starting at the age of 30 years (Han et al., 2013; van Twillert et al., 2015). This evidence concerns the gene CD4 and pertussis.