LIFE SPAN OF NAÏVE AND MEMORY T CELLS IN ADULT THYMETOMIZED RTAS

Abstract

P978 Aims: Life span of naïve and memory T cells in general is controversial. Inasmuch as immunological function of naive and memory T cell in adult thymecomized rats following a long-term thoracic duct drainage (TDD), has not been examined, we studied the life span of naïve and minor histocompatibility antigen H-Y-sensitized female LEW rats with respect to immunological T cell. Methods: Adult thymectomy was applied to female LEW rats. Anti-H-Y immunity in female LEW rats was established by immunization of female LEW rats by male LEW bone marrow cell (BMC) derived-DC. Employing a long-term thoracic duct drainage (TDD), i.e., more than 20 days, which heretofore has not been able to do so, and skin grafting were applied to examine whether and to what extent T cell mediated-immunity of naive and/or memory –induced female LEW rats to minor histocompatibility antigen H-Y was influenced. Results: Six months after adult thymectomy, naïve LEW female rats were found to reject to H-Y incompatible male isografts. Moreover, a long-term TDD method, i.e., more than 20 days or longer, combined with adult thymectomy was found to be so critical that the drained rats were not able to reject strong MHC-incompatible skin allograft. Furthermore, when it applied to minor H-Y-sensitized female LEW rats, it was demonstrated that the cells from the long term TDD-rats contained class II positive, thymus independent T cell-lineage cells (more than 80 %) which heretofore have not been described. Functional analysis of the male specific antigen H-Y sensitized LEW rats showed that 20 days-TDD female LEW rats were not able to reject male isografts. However, three to four weeks resting after the drainage, the resting female LEW rats were found to reject male isografts. Conclusions: Our studies demonstrated that life span of naïve T cells to minor histocompatibility antigen H-Y was relatively long, i.e., more than six months. Impairment of immunological T cell memory following a long-term TDD was associated with appearance of class II positive T cells and the transient dysfunction of T cell memory was functionally recovered by three to four weeks resting from a long term-TDD. To our knowledge this is the first report demonstrating the evidence for presence of long-lived naïve T cells to minor histocompatiblity antigen H-Y. Functional and transient impairment of immunological T cell memory associated with a long-term TDD was not due to the loss of memory T cell in TDL.