Age, thymopoiesis, and CD4+ T-lymphocyte regeneration after intensive chemotherapy

Rapid regeneration of immunity following chemotherapy may depend on the function of the thymus, an organ located in the upper chest that produces T lymphocytes. The thymus develops and functions throughout childhood, losing its function gradually after puberty. A study of 15 patients aged 1 to 24 years who had had extensive chemotherapy found an inverse relation between age and CD4+ T lymphocyte counts. The ability of the patients' bodies to regenerate CD4+ T lymphocytes after chemotherapy seemed to diminish with age. T lymphocytes are critical to healthy functioning of the body's immune system. The findings of this study suggest that any disease or therapy that decreases CD4+ T cells may affect adults more than children, as children may regenerate their T cell counts faster because of their functioning thymus. Study results may be applicable to treatments being developed for HIV-positive patients and for persons receiving bone marrow transplants to increase their immune responses.