| Research Abstract |
Physiological changes with increasing age are accompanied with immune disorder, including autoaggression which can be seen in age-different combinations of the responder-stimulator cells in the syngeneic host-versus-graft reactions, though the magnitude of the response depends on the tsrains of mice. Thus, footpad injection of irradiated spleen cells from one year-old BALB/c mice(H-2^d), but not from 2-mo-old young mice, into the young syngeneic mice evoked popliteal lymph node(PLN)-swelling, while this was not the case of DBA/2(H-2^d) mice.
The generation of autoreactivity was thought to be closely related with the change of T cell repertoire with age. Around one year of age, when only a small reduction in T cell number and an increase of CD8 T cell proportion in the periphery caused reduction of CD4/CD8 ratio, in comparison with younger mice, a proportion of Vb8^+ cells in BALB/c mice started increasing and became significantly high by two years of age. The increasing fraction of Vb8^
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+ T cells was caracterized by a low intensity of T cell receptors. Although both changes of T cell repertoire and development of the autoaggression may be approvable parameters for gaing, there was no direct correlation between them. They are probably under the defferent genetic controls.
Immune activities of Vb8^+T cells in the aged were investigated in response to Staphylococcus Enterotoxin B(SEB), an anigen corresponding to a T cell with Vb8-segment of TCR.In contrast to that young mice responded to the treatment with an increase of Vb8^+T cells, a majority of the aged mice died within a day of the treatment. Survivors from the toxin shock showed an increase of Vb8^+ T cells, though much less in magnitude as compared with young mice. In the spleen of the mice which died of the shock, but not of the survivors, the stary sky appearance which indicates apoptotic death of cells, developed in the white pulp. Thus, Vb8^+ T cells in the aged may not be silent but suicidally responding to an antigenic signaling. Less
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