Immunochemical relationship between natural haemagglutinins and immune antibodies in the toad (Bufo paracnemis).

Natural and induced antibodies from serum of Bufo paracnemis were isolated by specific immunoadsorption (natural antibodies and specific induced antibodies, respectively). Natural agglutinins specific to rabbit red blood cells (RRBC) showed, by immunodiffusion (ID) and by immunoelectrophoresis (IEP) against rabbit anti-B, paracnemis serum, at least three precipitation lines. Similar patterns were obtained with the specific induced antibodies. Immunochemical identity between natural and induced antibodies was observed by ID test. These results were assessed by repeatedly absorbing rabbit anti-Bufo serum with natural antibodies: these natural antibodies totally exhausted the activity of rabbit immune serum against specific anti-bovine serumalbumine and vice-versa. These reactions were studied using a very sensitive radioimmunodiffusion test. The heterogeneity of natural haemagglutinins and their identity with induced antibodies are discussed in relation with these experimental data.

Delayed hypersensitivity in tumor-bearing mice. In vitro activation of "eclipsed" spleen cells.

At various stages during the progressive growth of a transplanted sarcoma in BALB/c mice, the delayed hypersensitivity response to tumor antigen was determined using the food-pad swelling test (FPS) and the leukocyte migration inhibition assay (LMI). A close correlation was observed between the in vivo and in vitro assays. "Early" recognition of tumor antigen was detected 24 h after tumor inoculation by both techniques and this positive response was maintained until day 15. As the tumor grew larger, the delayed hypersensitivity response in vivo vanished, while the delayed hypersensitivity response in vitro disappeared about 3 days later. This suppression or "eclipse" of the anti-tumor cellular immune response was specific for the type of tumor used, and could be reversed in vitro by means of a low pH treatment of lymphoid cells.

Interferon induction by a tumoral DNA in an homologous culture system.

The interferon induction by Rous sarcoma DNA in an homologous culture system and a further insight of its kinetics and antimetabolites action were the principal aim of the present study. There was a direct relation between the dose of the inducer and the protection against the cytoplathogenic effect of the challenging virus (VSV) reaching the highest activity (68-75% CPE inhibition) with 100 mug RS-DNA. The kinetics of the induction revealed a peak inhibition by 18 hours after the inducer. Treatment with Actinomycin D evidenced that both interferon production and activity are modified. Its early addition resulted in a poor protection; but an accentuated interferon release was observed when antimetabolite was added 18 hours after the inducer. Similar results were obtained when its effect was studied on the activity of exogenous interferon. Interferon induction by Rous sarcoma DNA in an homologous system, allows the detection of a difference between tumoral and normal DNA at a biological level.