Difference between the lymph node response to injection of autosensitized T lymphocytes and that in a graft‐versushost reaction

Thymus (T) lymphocytes autosensitized in vitro were shown in previous studies to produce enlargement of draining popliteal lymph nodes upon injection into the footpads of syngeneic rats. Specific autoreactive effector lymphocytes were found to be recruited within these lymph nodes. In the present study, the cellular basis of lymph node enlargement in mice by autosensitized lymphocytes was compared with that produced in a graft‐vs.‐host (GvH) reaction. T lymphocytes of C3H mice were autosensitized against syngeneic fibroblasts in vitro for 16 to 18 h in the absence of serum, and 10 7 lymphocytes were injected into the footpads of syngeneic mice. Control lymphocytes were incubated without fibroblasts. The GvH reaction was produced by injecting 10 7 C3H T lymphocytes into the footpads of (C3H × C57BL)F 1 adult recipients. The index of relative enlargement of the draining popliteal lymph nodes was measured 6 days after injection. Experiments were done to identify the origin of the lymph node cells in these reactions. Irradiation of the donor lymphocytes (1000 r) or the recipient mice (550 r) was used to prevent proliferation of the lymphocytes of either origin. The participation of recipient T lymphocytes in lymph node enlargement was investigated by using thymectomized mice. The following results were obtained. 1) The GvH lymph node enlargement was found to depend on proliferation of the donor T lymphocytes, but did not seem to require the participation of radiosensitive cells within the recipient mice. 2) In contrast, the response of the lymph nodes to autosensitized donor T lymphocytes depended on the function of radiosensitive T lymphocytes within the syngeneic recipients. The autosensitized donor lymphocytes themselves did not have to proliferate to recruit the response of recipient T lymphocytes. 3) It was found that recruitment of recipient lymph node cells could be super‐imposed upon a conventional GvH reaction by presensitizing the C3H donor lymphocytes in vitro. Both autosensitization against syngeneic or allosensitization against C57BL fibroblasts augmented the lymph node response of (C3H × C57BL)F 1 hybrid recipients. The recruited or donor components of these mixed responses could be selectively abolished by irradiating either the donor lymphocytes or the recipient mice. Hence, the autosensitization response, like the host‐vs.‐graft transplantation reaction, can be induced by sensitization of lymphocytes peripherally and involves recruitment of lymphocytes within regional lymph nodes. The GvH response manifested in the same popliteal lymph nodes does not appear to require the recruitment of radiosensitive T lymphocytes. These findings suggest that different classes of T lymphocytes function in the autosensitization and GvH responses.