1. Walford, R.L.: The Immunologic Theory of Aging. Baltimore, Williams and Wilkins, 1969.
2. Saltzman, R.L., and Peterson, P.K.: Immunodeficiency of the elderly. Reviews of Infect. Dis., 9: 1127–1139, 1987.
3. Schwab, R., Staiano-Coico, L., and Weksler, M.E.: Immunological studies of aging. IX. Quantitative differences in T lymphocyte subsets in young and old individuals. Diagn. Immunol., 1:195–201, 1983.
4. DePaoli, P., Battistin, S., and Santini, G.F.: Age-related changes in human lymphocyte subsets: Progressive reduction of the CD4 CD45R (suppressor inducer) population. Cell. Immunol., 48: 290–296, 1988.
5. Roberts-Thompson, I.C., Whittingham, S., Young-chaiyud, U., and Mackay, I.R.: Ageing, immune response, and mortality. Lancet, ii: 368–370, 1974.