Search

In order to examine whether FcεRI-dependent degranulation of intestinal mast cells is required for expulsion of intestinal nematode Strongyloides ratti, CD45 exon6-deficient (CD45-/-) mice were inoculated with S. ratti. In CD45-/- mice, egg excretion in feces persisted for more than 30 days following S. ratti larvae inoculation, whereas in wild-type (CD45+/+) mice, the eggs completely disappeared by day 20 post-infection. The number of intestinal mucosal mast cells, which are known effector cells for the expulsion of S. ratti, was 75% lower in CD45-/- mice compared with that in CD45+/+ mice. Adoptive transfer of wild-type T cells from CD45+/+ mice into CD45-/- mice reduced the duration of S. ratti infection to comparable levels observed in CD45+/+ mice, with concomitant increases in intestinal mucosal mast cells. These results showed that CD45 is not involved in the effector function of intestinal mucosal mast cells against S. ratti infection. Since FcεRI-dependent degranulation of mast cells is completely impaired in these CD45 knockout mice, we conclude that FcεRIdependent degranulation is not required in the protective function of intestinal mucosal mast cells against primary infection of S. ratti.

SummaryIn this study, we have investigated that after the intraperitoneal infection with murine cytomegalovirus (MCMV), the CD3+ CD4– CD8–(double negative; DN) T-cell receptor (TCR)αβ+ T cells increased in peritoneal cavity, liver and spleen in both resistant C57BL/6 and susceptible BALB/c mice. The total cellular population of these cells showed peak levels around day 5 after infection in all the three investigated organs and the following phenotypical and functional characteristics emerged. The peritoneal DN TCRαβ+ T cells expressed highly skewed TCRVβ8 on day 5 after infection compared with the uninfected mice, but those in spleen and liver showed moderate and low skewed TCRVβ8, respectively. The percentages of NK1.1+ DN TCRαβ+ T cells gradually decreased as did modulation of some of their activation markers consistent with an activated cell phenotype. The peritoneal DN TCRαβ+ T cells on day 5 after infection expressed the genes of interferon-γ (IFN-γ), tumour necrosis factor-α, Eta-1 (early T-cell activation-1) and MCP-1 (monocyte chemoattractant protein 1) but lacked expression of interleukin-4 (IL-4). After in vitro stimulation with phorbol 12-myristate 13-acetate and calcium ionophore in the presence of Brefeldin A, higher frequencies of intracellular IFN-γ+ DN TCRαβ+ T cells were detected in all three investigated organs of infected mice compared with those of uninfected mice. Stimulation of peritoneal DN TCRαβ+ T cells with plate-bound anti-TCRβ monoclonal antibodies showed proliferation and also produced IFN-γ but not IL-4. These results suggest that DN TCRαβ+ T cells were activated and may have an antiviral effect through producing IFN-γ and some macrophage-activating factors during an early... [ABSTRACT FROM AUTHOR]

The differentiation process from CD4-CD8- double-negative (DN) thymocytes to CD4-CD8+ double-positive (DP) stage is accompanied by vigorous proliferation. The resulting DP cells contain a sizable proportion of large cycling cells, but most DP cells are small resting cells. To explore the molecular mechanisms which regulate cell proliferation of DP thymocytes prior to further development, we used TCR-transgenic (Tg) mice with non-selecting MHC (Tg-Neut), which contain almost exclusively DP thymocytes that are not subject to either positive or negative selection. In Tg-Neut, the thymus contained DP cells of relatively large size, which showed higher extracellular signal-regulated kinase activity and enhanced responsiveness to mitogen compared to small DP cells. This indicates that all the large DP cells in the thymus are not positively selected and that they possess proliferative potential. When Tg-Neut mice were backcrossed with CD45 knockout mice (CD45-/- Tg-Neut), the thymus showed an increase of large DP cells and cycling cells, but a decrease of apoptotic cells. Furthermore, Bcl-2 expression and Jun N-terminal kinase activity, which are associated with resistance to apoptosis, were enhanced. These observations suggest that thymocyte proliferation in the DP stage is suppressed by a CD45-related process with regulation of mitogen-activated protein kinase and Bcl-2 unless DP cells receive TCR-mediated signals. [ABSTRACT FROM PUBLISHER]

In mice lacking the src family protein tyrosine kinase, p 56lck (lck -/-), a greatly reduced number of peripheral T cells is observed due to a profound blockage of the thymocyte development. The peripheral T cells in lek -/- mice exhibit proliferative response after T-cell receptor (TCR) crosslinking, but can not respond to viral antigens. In this report, we examined the allo-responses of peripheral T cells in the lck-/- mice and the following results were thus obtained. (1) After an intravenous injection of fully allogeneic [allo-major histocompatability complex (MHC)] spleen cells, an increase of interleukin (IL)-2Rα+ cells was observed in both the CD4+ or CD8+ peripheral T cells of the lck-/- mice and the increase was similar to those in the lck+/+ littermate, with only a omewhat delayed and prolonged time kinetics observed in the CD4+ T cells of the lck-/- mice. (2) the lck-/- mice rejected the fully allogeneic trunk skin grafts several days later than the lck+/+ mice, but did not reject the minor allogeneic grafts. (3) The peripheral T cells of the graft- rejected lck-/- mice exhibited a weaker but significantly proliferative response, while the cytotoxic T lymphocyte (CTL) activities to allo-MHC antigens in vitro were comparable to those in lck+/+ mice. While the response to the minor allo-antigens was shown by the peripheral T cells in the lck+/+ mice with minor allogeneic skin grafts but not by those in the lck-/- mice with the grafts. These results thus suggest that p56lck is not essential for peripheral T cells to both respond and exhibit effector functions to allo-MHC antigens. [ABSTRACT FROM AUTHOR]

In order to search for a possible role of abnormally proliferating T cells in developing autoimmune disease in lpr mice, and to define the difference of the T ceils among various lpr-congeneic mice with different clinicopathological findings, the T-cell receptor (TcR) Vβ gene expression in the enlarged lymph nodes (LN) of C3H/HeJ-lpr/lpr (C3H-lpr), C57BL/6-1pr/lpr (B6-lpr) and MRL/Mp-lpr/lpr (MRL-lpr) mice was analysed. A RNA blot analysis using several Vβ-specific probes showed that the Vβ3 gene, whose products are important for recognizing Mlsb/a, was used in B6-lpr and MRL-lpr with the Mlsb/b but not in C3H-lpr with the Mlsb/a. The Vβ5 gene, which is selectively related to I-E molecules, was predominantly used in B6-lpr(I-E-) but not in C3H-lpr(I-E+) nor MRL-lpr(I-E+). Similarly, the V12 gene was also expressed in B6-lpr but not in C3H-lpr. To compare in detail the Vβ repertoire among lpr mice with different major histocompatibility complex (MHC) backgrounds, the Vβ gene sequences in the cDNA libraries from LN cells of C3H-lpr were analysed, following the recent investigation of B6-lpr mice (Ohga et al., 1989). Eleven β-chain cDNA out of 32 β cDNA in B6-lpr and 24 β-chain cDNA out of 55 β cDNA in C3H-lpr were found to contain sequences with open reading frames that potentially encode functional TcR β-chain. The fequencies of the messages in the cDNA libraries from these mice were consistent with the RNA blot analysis using Vβ3- and Vβ5-specific probes. It was notable that 36% of the functional β-chain mRNA in B6-lpr and 50% of the β mRNA in C3H-lpr expressed the Vβ8 gene family. When the TcR Vβ gene expression was compared between the LN cells in C3H-lpr, B6-lpr and MRL-lpr, as reported by Singer et al. (1986), the usage of Vβ genes other than the Vβ8 gene family in B6-lpr (H-2b) LN cells differed significantly from those in C3H-lpr (H-2k) and MRL-lpr(H-2k). The results presented here indicate that the usage of Vβ genes is heavily influenced by the genetic background of lpr mice, similar to normal mice, but with preferential usage of the Vβ8 gene family as a common structural feature in lpr gene-induced cell populations. [ABSTRACT FROM AUTHOR]

To search the abnormality in prethymic T-cell precursors in lpr/lpr(lpr) mice, rearrangement and expression of T-cell receptor (TcR) genes were investigated in long-term cultured bone marrow (LTBM) cells of lpr mice, in which the developmental steps of T-cell purcursors may be better synchronized than those in bone marrow (SM) cells. Neither rearrangment nor expression of TCR γ and δ genes were detected in the LTBM cells from +/+ control mice, whereas some γ gene rearrangements were detected in those derived from lpr mice, irrespective of the genetic background. When BM cells or LTSM cells from lpr mice were transplanted into supralethally irradiated +/+ mice, the lpr-derived BM cells appeared earlier in the thymus of the recipient mice than +/+-derived BM cells and the recipients suffered from lethal wasting syndrome. In addition, the lpr-derived SM cells showed higher activity in colony-forming unit spleen (CFUs) than the +/+-derived SM cells. These results suggest that the T-cell progenitors in the SM of lpr mice may be different not only in quantity but also in quality from those of +/+ mice. [ABSTRACT FROM AUTHOR]

We have previously shown that extrathymic rearrangements of T-cell receptor (TcR) γ and δ chain genes occur in the peripheral lymphoid tissues of athymic nude mice. To further determine where the TcR gene rearrangements occur in nude mice, we investigated the rearrangement and expression of the TcR genes in the long-term cultured bone marrow (LTBM) cells which were homogenous in developments without mature T cells as assessed by FACS analysis. The LTBM derived from euthymic mice contained IcR γ and δ chain genes in germline configuration, while gene rearrangements of both locus were detected in the LTBM cells from nude mice. These results suggested that γ and δ gene rearrangements do occur in the bone marrow cells of nude mice and that the T-call precursors in bone marrow may be increased in frequency in such animals. [ABSTRACT FROM AUTHOR]

An autosomal recessive gene, lpr, is responsible for lymphoproliferation and autoimmunity of lpr mice, in which background genes are also known to influence the development of autoimmune disease. To define the differences in abnormally proliferating T cells between C57BL/6-lpr/lpr and MRL/Mp-lpr/lpr mice, and to try and understand the influence of background in the differing expression of autoimmune disease in both strains, we analysed the sequences of T cell antigen receptor Vβ genes expressed in the cells from the enlarged lymph nodes of C57BL/6-lpr/lpr mice. Eleven β cDNAs out of the 38 Cβ-specific cDNAs contained sequences with open reading frames from the beginning of the variable region to the expected termination codons at the end of the constant regions. Notably, 36% of the functional β-chain mRNAs expressed Vβ8.3 genes, whereas Vβ8.3 and Vβ8.2 genes were not found. These results are consistent with a relatively lower frequency of the Vβ8.1 or Vβ8.2 expressing cells in the hypertrophic lymph nodes of C57BL/6-lpr/lpr mice, detected by KJI6-133 monoclonal antibody. Interestingly, other Vβ genes expressed in these mice were completely distinct from those in MRL/Mp-lpr/lpr mice as described by Singer et al (1986), The different distribution of Vβ genes expressed in C57BL/6-lpr/lpr from that in MRL/Mp-lpr/lpr mice might be related to the differences in the genetic background and the expression of lpr gene-associated autoimmunity. [ABSTRACT FROM AUTHOR]