Reconstitution of lymphoid tissues under the influence of a subclinical level of graft versus host reaction induced by bone marrow T cells or splenic T cell subsets.

Reconstitution of lymphoid tissues under the influence of subclinical graft versus host reaction (GVHR) has been investigated. Lethally irradiated AKR mice were reconstituted with B10 bone marrow (BM) cells which had been treated with anti-Thy-1 antibody alone without complement (GVHR chimera). Their immunological reconstitution was analyzed and compared with that of AKR recipients which had been reconstituted with B10 BM cells treated with anti-Thy-1 antibody plus complement (control chimera). One hundred percent of both chimeras survived more than 100 days without showing clinical signs of GVHR. However, full donor chimerism was accomplished at an early stage after reconstitution in the former GVHR chimeras, whereas a substantial number of recipient T cells persisted in control chimeras for the entire observation period. When reconstitution of various lymphoid tissues was compared between control and GVHR chimeras, no difference in the reconstitution of the thymus and spleen was noted. By contrast, the cellularity of peripheral lymph nodes in GVHR chimeras was regularly considerably lower than that of the control chimeras. The apparent insufficiency of lymph node reconstitution appeared to be attributable to the impairment of lymph node structure itself which may be involved in lymphocyte homing. Furthermore, clonal deletion of V beta 6+ T cells which are reactive to recipient (Mls-1a) antigens was abrogated in the GVHR chimeras but was normally induced in the more completely T cell-depleted control chimeras. This abrogation of clonal deletion of V beta 6+ T cells appeared to result from the early disappearance of recipient T cells in these chimeras. Thus, it appeared that donor T cells in the BM that survive anti-Thy-1 treatment in vitro plus subsequent BM transplantation induced a subclinical level GVHR which contributed to the full donor chimerism as well as abrogation of clonal elimination of V beta 6+ donor T cells. Indeed, inoculation of CD8+ T cells along with the transplantation of the T cell-depleted BM cells (anti-Thy-1 plus C-treated cells) from donor mice into the AKR recipients was also shown to induce a similar state in the recipients.