| Abstract: | A study has been made of cytological and histological changes in lymph nodes draining grafts of allogeneic skin or tumour. The two types of graft provoked mitosis of both thymus- and bone-marrow-derived lymphocytes; this activity was associated with reactive changes initially in the paracortex and then in germinal centrts and medullary cords. Grafts of allogeneic skin evoked two peaks of mitosis which declined rapidly as the graft was rejected. Transient mitotic activity also occurred in response to (control) syngeneic skin, coinciding with increased lymph-node weight and some paracortical hyperplasia but (cf. changes found after allografting), other parts of the node did not respond. Allogeneic EL4 lymphoma cells gave rise to a greater and more rapid immunological response than did skin grafting. The mitotic response to the injected tumour cells failed, at least in the draining lymph nodes, long before death of the host due to progressive tumour growth. It is suggested that both the greater mitotic response, and its later failure, are related to the progressive growth of the tumour and to the everincreasing antigenic burden which such a tumour represents. |
