Migration and cell recruiting activity of specifically sensitized lymphocytes in sponge matrix allografts

The migration of indium-III-labeled specifically sensitized lymphocytes (SSLs) and unsensitized spleen lymphocytes (ULs) into sponge matrix allografts was studied in irradiated mice. Intravenously injected SSLs were preferentially recruited to the graft bearing the sensitizing alloantigen. High numbers of these SSLs, however, were attracted regardless of their immunological specificity to a third-party graft, when cells sensitized against the third-party antigen were given simultaneously. When SSLs were injected locally into a specific and third-party graft, i.v. injected ULs also homed preferentially to the specific graft. Prior treatment of SSLs with anti-theta serum and complement abrogated their cell recruiting capacity. The percentage of injected lymphocytes recruited to the specific allograft during the first 36 hr increased with the number of SSLs injected. The duration of augmented lymphocyte recruitment, however, was inversely related to the number of SSLs injected into the graft. Furthermore, there is some evidence that SSLs which have been recruited to an allograft migrate to a second site of antigen challenge and initiate there a high lymphocyte recruitment. These results suggest that increased lymphocyte recruitment to an allograft is initiated by an immunologically specific interaction between SSLs and alloantigen. The cells, however, which are preferentially recruited to an allograft, comprise small unsensitized lymphocytes and SSLs regardless of their immunological specificity. Lymphocytes with cell recruiting activity are T cells and appear to be very mobile in vivo. The mechanism described might have an important amplifying effect on allograft rejection.