These observations are often a characteristic feature of the development of PID, including a decrease in the number of T lymphocytes and a decrease in the CD4 to CD8 ratio (this ratio is reduced even to <1), as well as a reduced number of B lymphocytes; these changes may indicate an impaired response of the body to all kinds of infections that often accompany PID, including patients with CVID. The gene discussed is CD4; the disease is pelvic inflammatory disease.