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Depression of Homograft Rejection and Graft-versus-Host Reactivity following 7,12-Dimethylbenz(a)anthracene Exposure in the Rat¹

Istituto di Patologia Generale, Facoltà di Medicina e Chirurgia, Università di Bologna, 40126 Bologna, Italy

An attempt to demonstrate a significant depression of cell-mediated immunity at the beginning of carcinogenesis by chemicals was made in the rat by skin homografts and graft-versus-host assays. A weak but highly significant prolongation of survival time was observed when F344 skin grafts were performed, across a weak (non-AgB) histoincompatibility, in Lew rats 10 to 13 days after 7,12-dimethylbenz(a)anthracene treatment was started. The impairment of graft-versus-host reactivity of F344 spleen cells from donors given 7,12-dimethylbenz(a)anthracene 5 to 8 days before the assay was more evident when either weak (F344 x Lew F₁) or strong (F344 x Bf F₁) histocompatibility antigens were challenged. Further graft-versus-host assays with cells from the donor sensitized against the hybrid partner were performed in order to investigate the mechanism of cell-mediated immunity damage. There was no difference in sensitization lowering of 7,12-dimethylbenz(a)anthracene-treated animals whether the carcinogen was given before or after sensitization. This suggests that lymphocytic damage occurs in cell-mediated immunity depression, while this type of immunity does not show the early, remarkable damage characterizing the humoral processes.

¹ Supported by a grant from Consiglio Nazionale delle Ricerche, Rome, Italy.

Received 12/11/70. Accepted 5/ 7/71.