Effect of thymosin alpha one on specific antibody response and susceptibility to infection in young and aged mice.

The antibody response to a variety of antigens has been shown to diminish with age. We investigated the capacity for Thymosin Alpha One (T alpha 1) treatment to augment antibody production in tetanus toxoid (TT) and pneumococcal capsular polysaccharide (PN) inoculated young and old mice. We also measured survival of these immunized mice after aerosol exposure to Streptococcus pneumoniae. As predicted antibody response to TT, but not PN, was significantly reduced in the old animals and T alpha 1 augmented antitetanus antibody in both young and old mice. T alpha 1 did not have an effect on anti pneumococcal antibody production. All mice that had received PN did have an antibody response, yet survival after exposure to the organism was strikingly less in the old animals. Our data support the contention that antibody response to T-dependent antigens (such as tetanus toxoid) falls with aging but can be reconstituted somewhat by thymic factors. Furthermore, for T-independent antigen (such as pneumococcal capsular antigens) the age-related changes are less evident. In the latter situation, the presence of a brisk antibody response after vaccination was not sufficient to prevent pneumonia and death in old animals.