Lymphocyte reactivity in normal and malignant cell proliferation against a phylogenetically conserved antigen in fetal extracts.

Lymphocyte reactivity to 3-M KCl extracts from fetuses of different species of origin was shown by the macrophage electrophoretic mobility (MEMB) and/or the leukocyte migration inhibition tests in tumor-bearing mice and humans. In chemical carcinogenesis, reactivity was detectable before tumors developed. Six weeks after sc injection of 1,000 micrograms benzo[a]pyrene [(BP) CAS: 50-32-8] into XVII/Bln mice, the MEMB test became positive. The latent period was 15 weeks after 1.0 micrograms BP, indicating a dose-response relationship of the phenomenon. Painting of mouse skin with 7,12-dimethylbenz[a]anthracene [(DMBA) CAS: 57-97-6], croton oil (CAS: 8001-28-3), or benzene (CAS: 71-43-2) had the same sensitizing effect as BP. In contrast to the strong carcinogens BP and DMBA that caused lymphocyte reactivity to persist until tumors developed, benzene and the promoter croton oil induced only a transient effect. Termination of treatment abolished reactivity within 12 weeks. Lymphocyte reactivity to fetal extract in normal cell proliferation was evident from the fact that two-thirds-hepatectomized rats and BCG-treated mice became MEMB-positive. In hepatectomized rats the effect was reversible according to the completion of liver regeneration. Lymphocytes from tumor-bearing mice reacted with mouse and human fetal extract as well as with extracts from different developmental stages of frogs and fish. Fetal extracts were assumed to contain a phylogenetically conserved antigen.