THE IMMUNE-RESPONSE TO TETANUS IN ELDERLY PEOPLE - SHORTENED IMMUNOLOGICAL MEMORY AFFECTS THE DURATION OF PROTECTION

Infectious diseases represent one of the most frequent causes of morbi dity and mortality in the elderly. Little information is yet available on the state of immunization against well-known antigens such as teta nus toroid (TT) in old age. It was, therefore, the aim of this study t o analyze antibody titres and peripheral blood mononuclear cell (PBMC) reactivity to TT in healthy SENIEUR compatible young (< 30 years, n = 25) and old (> 65 years, n = 32) blood donors. TT-specific antibodies were measured by the ELISA technique; PBMC proliferation was assessed by H-3-thymidine incorporation analysis. In the young group TT antibo dy titres were detectable in all but two individuals, whereas 60% of t he old persons had no detectable TT antibodies. This seemed partly to be due to a shortened immunological memory in old age, since 32% of th e aged persons without TT antibodies had been vaccinated within the pa st 10 years, 21% even 3 to 6 years prior to investigation. TT antibody concentrations were normal in aged individuals vaccinated within the past two years. Peripheral blood lymphocytes from all but two persons without antibody titres did not proliferate when stimulated with TT in vitro, indicating that no memory T cells were available to reinduce a n efficient immune response. Our results suggest that the tetanus vacc ination strategy practised in Austria does not guarantee full protecti on in the elderly.