Immunity to a syngeneic sarcoma induced in rats by dendritic lymph cells exposed to the tumour either in vivo or in vitro.

Rats were prepared surgically so that peripheral intestinal lymph could be collected from them while a syngeneic tumour (the HSN sarcoma) was growing in each major Peyer's patch of the small intestine. Dendritic lymph cells were isolated from the lymph and injected i.p. into naive, syngeneic rats. Each of the 16 recipients received just under 10(6) such cells and was challenged 10 days later with a subcutaneous dose of 10(4) viable HSN cells. Six weeks after this challenge only 7 of the recipients had a tumour and these were small (mean weight 1.8 g), while 17 controls (which had each been treated with 10(6) thoracic duct lymphocytes from the same donors, and given the same challenge) all had large tumours (mean weight 8.8 g). The remaining 9 test rats were still free of tumours when they were killed and autopsied 4 months after challenge. Dendritic lymph cells from normal rats were 'sensitised' by incubating them overnight on a monolayer of HSN cells. They were then transferred to 5 naive recipients which received the usual challenge. Six weeks later they all had tumours (mean weight 1.3 g) but these were much smaller than those in the 5 controls (mean weight 9.3 g).