Immunological specificity and the kinetics of T-suppressor induction in the immunization of mice with allogeneic spleen

A high dose immunization of mice with gamma-irradiated allogeneic spleen cells has been shown to induce, in a recipient spleen, specific suppressor T-cells, resistant to mitomycin C, which are capable of inhibiting DNA synthesis and, to a lesser degree, the generation of killer cells in the mixed lymphocyte culture (MLC). The maximum suppressor activity is reached on days 3-6 after immunization. Both reactions are blocked mostly in those stimulator cells which bear H-2 antigens used for immunization. In contrast, DNA synthesis is inhibited only slightly, if at all, when it is stimulated in MLC by third-party cells, even if these are added to the culture as a mixture with correspoding stimulators. Unlike X-irradiated allogeneic cells, the untreated ones induce a mixture of suppressors, T-cells and macrophages, with a considerable non-specific suppression. Untreated syngenic lymphoid cells induce less active non-specific suppressors with properties of macrophages.     

The growth of preneoplastic hepatocytes in the spleen of recipient mice]

Hepatocytes and the fraction of non parenchymal cells enriched with oval cells were extracted from the preneoplastic mouse liver at the stage of hyperplastic node formation and implanted into the spleen. In 14-16 months after the transplantation, multiple islets of hepatocytes which replaced up to 25% of the spleen cut area, were found in 57% (4 of 7) and 22% (8 of 36) of recipients respectively. The hepatocytes formed 2-3-cell bulks or solid masses organized into multicellular trabecules, and expressed biliary capillary antigen, albumin and transferrin. In the inoculation of nonparenchymal cell fraction, the growth of hepatic tissue in the spleen depended on the magnitude of hepatocyte admixture to be undetectable in absence of hepatocytes in the donor suspension. The growth of hepatic tissue in spleen was observed following the injection of a small number (3 x 10(-4)-6 x 10(-5)) of live hepatocytes. This fact evidences an extremely high clonogenic potency of clonogenic potency of preneoplastic hepatocytes.     

DNA damage in the spleen, liver and kidneys of mice treated with ochratoxin A

Ochratoxin A a natural contaminant of feed and food has been shown to induce experimental liver and kidney tumors. Since there is a good correlation between the carcinogenic potency of chemicals and the DNA damages induced in mammalian cells treated either in vivo or in vitro by these compounds, we have measured single-strand breaks induced by ochratoxin A in DNA of liver, spleen and kidney. Our data clearly showed that ochratoxin A induced DNA damages in vitro as well as in vivo. Damages were dose-dependent, reversible and vary upon the time according to the tissue. In spite there is no report up to now on experimental leukemia induced by ochratoxin A, our results indicate that this possibility have to be considered.     

Selected phenotypic induction of null lymphocytes from mice with thymic and nonthymic agents

Induction of phenotypic membrane markers upon null lymphocytes with five thymic and four nonthymic preparations was compared using two different bioassays. The thymic extracts thymosin fraction V and Leucotrofina and thymic peptides α₁-thymosin and thymopoietin induced Thy 1.2 antigen even in the presence of dl-propranolol, but did not induce surface membrane Ig. A synthetic analog of facteur thymique serique, isoproterenol, poly(A:U), and ubiquitin induced both T- and B-cell markers; this induction was blocked with dl-propranolol. Induction with cyclic AMP was also partially blocked with dl-propranolol. The spleen was as rich in inducible lymphocyte precursors as was bone marrow. None of the nine agents were effective at inducing T-cell antigen on null cells from aged mice. Induction with all nine agents probably involved prostaglandin synthesis, since this effect was inhibited with 1 μg/ml indomethacin.     

Effect of the spleen extracts on primary immune response in mice]

Experiments were conducted on mice. Direct Jerne's test demonstrated a possibility of intensification of the primary immune response in the sexually mature mice under the effect of the splenic extracts. The significance of the extract dose and of the time of administration for the manifestation of the stimulating action was studied.     

Bactericidal effects of macrophages of mice treated with interferon]

The preparations of interferon or virus-inhibiting factor produced in L cell (L-IF) and mouse brain (MB-IF) enhanced the killing of Staphylococcus aureus (S.a.) by the mouse peritoneal macrophage. The L-IF, heat-inactivated at 80 degrees or 60 degrees for 30 min., and mock L-IF could not enhance the killing of S.a. The heterologous human and rabbit interferon preparations didn't enhance the bactericidal activity of macrophage. The L-IF didn't have any effect on the release of lysozyme from the macrophages.     

Chromosome damage in the bone marrow of mice treated with the methylating agents methyl methanesulphonate and N-methyl-N-nitrosourea in the presence or absence of caffeine, and its relationship with thymoma induction.

A single dose (0.8 mmole/kg) of N-methyl-N-nitrosourea (MNUA) causes significantly more chromosome damage in the bone marrow of mice than a dose of equal toxicity to the animals, (1.1 mmole/kg) of methyl methanesulphonate (MMS) 6, 24 and 48 h after treatment. At these doses both agents alkylate bone-marrow DNA to similar extents, but only MNUA induces thymic lymphomata. The greater chromosome-damaging effects of MNUA are ascribed to the known differences in the pattern of DNA alkylation by each agent, in particular the much higher levels of O-6 methylguanine and phosphotriesters produced by MNUA. The greater chromosome-damaging effect of MNUA may account for its higher toxicity to the bone marrow which in turn may be a significant factor in the induction of thymomata. The enhancement by caffeine of chromosome damage seen particularly 48 h after MMS-treatment suggests that post-replication repair protects cells from the effects of DNA-methylation in vivo.     

Stimulator of proliferation of spleen colony-forming cells in T-cell deprived mice treated with cyclophosphamide or irradiation

A role for T-cells in the regulation of CFU-S proliferation was investigated by determining the presence and activity of CFU-S proliferation stimulator (CFU-S stimulator) in adult mouse bone marrow after irradiation or cyclophosphamide (Cy) treatment. CBA mice previously deprived of T-cells by thymectomy, irradiation and bone marrow reconstitution (TIR) were thereafter treated with 4.5 Gy irradiation or 200 mg/kg Cy. Regenerating bone marrow cells of TIR and corresponding control mice after irradiation or Cy treatment produced CFU-S stimulator. The dose dependent increase in cytosine arabinoside cell death of normal bone marrow day 8 CFU-S was found when both CFU-S stimulators obtained after irradiation of TIR or corresponding control animals were tested. CFU-S stimulator activity in the bone marrow of TIR-Cy treated mice was also detected, but the effect was not dose-dependent. This was not related to the presence of an inhibitor of CFU-S proliferation. It appears that the CFU-S stimulator activity is not related to IL-6, IL-1 or IL-2, or to an inhibitor of IL-6 or IL-1 activity. The results demonstrate the existence of CFU-S proliferation stimulator unrelated to the two major monokines in the bone marrow of immunosuppressed mice.