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Helicobacter pylori is the major causative agent of chronic antral gastritis and is thought to be involved in the pathogenesis of mucosa-associated lymphoid tissue lymphoma (MALToma) developing in the human stomach. The aim of this study was to clarify whether corporal autoimmune gastritis (AIG), which is known to decrease acidity due to destruction of parietal cells, predisposes mice to H. pylori infection, thereby leading to MALToma-like pathology. BALB/c mice in which AIG had been induced by thymectomy 3 days after birth (AIG mice) were used. The AIG mice were orally administered mouse-adapted H. pylori at the age of 6 weeks and were examined histologically and serologically after 2 to 12 months. The results were compared with those obtained from uninfected AIG mice and infected normal mice. Germinal centers were induced in the corpus in 57% of the H. pylori-infected AIG mice, which elicited anti-H. pylori antibody responses in association with upregulation of interleukin-4 (IL-4) mRNA. In these mice, parietal cells remained in the corpus mucosa. These findings were in contrast to those with the uninfected AIG mice: fundic gland atrophy due to disappearance of parietal cells associated with upregulation of gamma interferon, but not IL-4, mRNA and no germinal center formation in the corpus. These observations suggest that AIG alters the infectivity of H. pylori, leading to MALToma-like follicular gastritis, at an early stage after H. pylori infection.

We isolated and sequenced a cDNA clone of the human gene encoded by the 5' half of the ret transforming gene. The nucleotide sequence indicates that it encodes a protein with "finger" structures which represent putative metal- and nucleic acid-binding domains. Transcription of this gene was detected at high levels in a variety of human and rodent tumor cell lines, mouse testis, and embryos. In addition, a unique transcript was observed in testis RNA. When the expression of the unique transcript was examined at different stages of spermatogenesis, a striking increase in mRNA levels accompanied progression from meiotic prophase pachytene spermatocytes to postmeiotic round spermatids. This finger-containing gene may thus function in male germ cell development.

The alymphoplasia (aly) mutation of mice causes the systemic absence of lymph nodes, Peyer's patches and well-defined lymphoid follicles in the spleen. We found that antibody responses are elicited, albeit weakly, to either T cell-dependent or T cell-independent antigen by aly/aly mutants. However, isotype switching was defective. The T cell-dependent immune response was not elicited in splenectomized aly/aly mice. Neither hypermutation nor germinal center formation was observed in aly/aly mice. These results suggest that T-B collaboration requires either lymph nodes or spleen, and that hypermutation and affinity maturation depend on germinal center formation.

HRS/J inbred mice carry a mutant autosomal recessive gene (hr), which in homozygotes coincides with susceptibility to spontaneous thymic leukemia. Unlike their heterozygote (hr/+) littermates, hr/hr homozygotes express high levels of xenotropic virus during the preleukemic period, and viruses with a broadened host range (termed polytropic viruses) can be isolated from their preleukemic and leukemic tissues. Because hr/hr and hr/+ mice are otherwise genetically identical, the virological differences between them support the role of polytropic viruses in the generation of thymic leukemia. In the present report we show that the HRS/J polytropic viruses are env gene recombinants with unique oligonucleotide and peptide maps. These polytropic viruses appear to arise by recombination between ecotropic virus and an unidentified genome related, but not identical to, the endogenous xenotropic viruses. Moreover, polytropic viruses not only accelerate leukemogenesis in HRS/J mice, but also induce thymic leukemia in the low leukemia strain CBA/J. By contrast, cloned ecotropic and xenotropic viruses have no leukemogenic action.

We established and characterized a systematic ultraviolet light-induced carcinogenesis model using KSN nude mice. We prepared five groups of KSN mice and exposed them six times a week to five levels of daily ultraviolet B (UVB) doses; 1340, 670, 320, 160 and 0 J/m2/day. In 670, 320 and 160 J/m2/day, the latency period tended to become shorter in proportion to the daily doses and prevalence data fitted well to log-normal distribution. In the log-log plot of days till 50% prevalence versus daily dose, we saw a linear relationship for 1 mm tumor diameter. From this analysis, we determined that days necessary to reach 50% prevalence is in proportion to the -0.49 power of daily dose. The average number of tumors per survivor correlated with prevalence data. Direct measured rates of tumor growth were independent of daily UVB-dose. Therefore we speculated that UV-irradiation did not affect tumor growth after its appearance. Most UVB-induced tumors were squamous cell carcinoma, the rest were spindle cell carcinoma, papilloma and mixed type. We concluded that our experimental data with nude mice was in accordance with data with hairless mice in nature.

To gain an insight into the relationship between UVB-carcinogenesis and natural killer activity, we examined ultraviolet light-induced carcinogenesis in mice with high natural killer, activity (KSN) and mice with natural killer deficiency (KSN-bg). We exposed mice six times a week to three levels of daily ultraviolet B (UVB) doses; 320, 160 and 0 J/m2/day. During the latency period of skin tumor development in KSN mice, we detected no suppression of the natural killer activity at both 320 and 160 J/m2/day. Even at 1340 J/m2/day, we could not detect any significant suppression of NK activity in KSN mice. When we irradiated spleen cells in vitro, we observed NK activity suppression. Next, we compared the carcinogenic effects of UVB-irradiation on KSN and KSN-bg mice. At 320 J/m2/day, we detected no significant differences between them. In contrast, at 160 J/m2/day, KSN-bg mice showed a significantly higher rate of skin tumor induction than KSN mice (p < 0.05). Most UVB-induced tumors were squamous cell carcinoma, the rest were spindle cell carcinoma, papilloma and mixed type. Our results suggest that NK activity plays a protective role against UVB-carcinogenesis from low daily-doses of UVB-irradiation.

Characterization of tumors that arise spontaneously in the AKR mouse indicates that they are derived from cells of a distinct T-cell lineage. Cells in this subclass bear surface antigens, designated Tpre, Tthy, Tind, and Tsu, which are encoded by genes in the Tsu linkage group on murine chromosome 12. We have examined the rearrangement and expression of genes encoding the T-cell alpha, beta, and gamma chains in these tumors. Although these cells contain alpha-chain mRNA, they do not produce a normal-sized beta-chain mRNA. Most of them also lack gamma-chain mRNA. Each thymic leukemia was derived from a cell arrested at a different stage of development as defined by their expression of terminal deoxynucleotidyl transferase and Thy-1 mRNA. The data presented here are consistent with a model in which thymocytes expressing Tpre, Tthy, Tind, or Tsu undergo somatic development parallel to the development of other T cells. However, these thymocytes do not appear to differentiate into cells bearing alpha-beta heterodimers of the T-cell antigen receptor.