Biomedical subjects

K Kishihara

Publications and source records attributed to K Kishihara.

At least 37 records · Page 2Linked to original sources

PubMed1998

Differential requirements of CD45 protein tyrosine phosphatase for cytolytic activities and intrathymic and extrathymic development of intestinal intraepithelial lymphocytes.

CD45 is a transmembrane protein tyrosine phosphatase essential for Ag receptor-mediated signaling in both T and B cells. In this study we investigated roles of CD45 in development and cytolytic activities of murine intestinal intraepithelial lymphocytes (i-IEL) using CD45 exon 6 knockout (CD45-/-) mice. Interestingly, the total cell number of i-IEL was significantly reduced in CD45-/-mice during aging (10-20 wk of age), whereas the i-IEL number was normally increased in the wild-type littermates. Especially, the number of gamma(delta)TCR+ i-IEL decreased markedly in CD45-/- mice during aging. The i-IEL in CD45-/- mice were more susceptible to in vitro spontaneous apoptosis than the normal i-IEL, implying that CD45 is required for maintenance of the cellularity of i-IEL. Results from in vivo analyses of the extrathymic and intrathymic development of i-IEL suggested that CD45-mediated signaling is required for the intrathymic, but not the extrathymic, development of i-IEL. Moreover, the whole i-IEL from CD45-/- mice showed a significantly reduced cytolytic activity, and the residual cytolytic activity was completely diminished by depleting CD45+ i-IEL, suggesting that CD45 is indispensable for the TCR-mediated cytolytic activity of i-IEL. Furthermore, we found differential contributions of CD45 and p56lck to development and induction of cytolytic activities of i-IEL.

Animals↗

PubMed1998

Receptor-specific allelic exclusion of TCRV alpha-chains during development.

Expression of a single Ag receptor on lymphocytes is maintained via allelic exclusion that generates cells with a clonal receptor repertoire. We show in normal mice and mice expressing functionally rearranged TCR alphabeta transgenes that allelic exclusion at the TCR alpha locus is not operational in immature thymocytes, whereas most mature T cells express a single TCRV alpha-chain. TCRV alpha allelic exclusion in mature thymocytes is regulated through a CD45 tyrosine phosphatase-mediated signal during positive selection. Using functional and genetic systems for selection of immature double TCRV alpha+ thymocytes, we show that peptide-specific ligand recognition provides the signal for allelic exclusion, i.e., mature T cells maintain expression of the ligand-specific TCRV alpha-chain, but lose the nonfunctional receptor. Whereas activation of TCRV beta-chains or CD3epsilon leads to receptor internalization, TCRV alpha ligation promotes retention of the TCR on the cell surface. Although both TCRV alpha- and TCRV beta-chains trigger phosphotyrosine signaling, only the TCRV beta-chain mediates membrane recruitment of the GTPase dynamin. These data indicate that TCRV alpha-directed signals for positive selection control allelic exclusion in T cells, and that developmental signals can select for single receptor usage.

Alleles↗

PubMed1998

Effect of a traditional Chinese medicine, Bu-zhong-yi-qi-tang on the protection against an oral infection with Listeria monocytogenes.

The protective effect against an oral infection with Listeria monocytogenes was observed in BALB/c mice who were orally administered a traditional Chinese medicine, Bu-zhong-yi-qi-tang (Japanese name: Hochu-ekki-to, HOT) daily for 7 days. Bacterial numbers in the Peyer's patch (PP) at 18 h, in the mesenteric lymph nodes (MLN) at 18 h, 1 day and 3 days and in the liver at 3 days after infection were significantly suppressed in HOT-treated mice, although there was no difference in the bacterial number in the small intestinal contents. The enhanced bactericidal activities of PP and liver macrophages by pretreatments of HOT were observed. The protective effect of HOT was not observed in athymic nu/nu and IFN-gamma deficient mice. The administration of HOT increased IFN-gamma-producing cells in the intestinal intraepithelial lymphocytes (IEL) but did not in the PP, MLN and liver. HOT exerts effects mainly on CD8alphabeta+ IEL which are thymus-dependent, and induced IFN-gamma production from their cells. These results suggest that HOT acts on the gut-associated lymphoid tissues and induces IFN-gamma from CD8alphabeta+ IEL, which activates PP and liver macrophages and consequently the resistance to L. monocytogenes is augmented in the mice.

Animals↗

PubMed1998

Beta-selection of immature thymocytes is less dependent on CD45 tyrosinephosphatase.

Tyrosine kinase p56lck plays a pivotal role in beta-selection from CD4-8- (DN) to CD4+8+ (DP) developing pathway, but it is unclear how CD45 transmembrane tyrosinephosphatase is involved in this process although CD45 activates p56lck by dephosphorylating its tyrosine-505. To analyze this issue, we produced double mutant mice of T-cell receptor transgenic mice (TCR-Tg) or RAG-2 knock out mice backcrossed with either p56lck or CD45 knock out mice. In TCR-Tg, CD25+DN thymocytes almost disappeared and CD25-44-DN cells of further developing stage increased, implying that all DN thymocytes can undergo beta-selection due to the expression of functionally rearranged TCR-beta on CD25+ DN thymocytes. However, CD25+ thymocytes increased in DN stage when TCR-Tg were backcrossed with p56lck deficient mice but not with CD45 deficient mice. Similarly, DP thymocyte induction with CD25+ cell reduction in RAG-2 knock out mice by injection of anti-CD3 mAb was inhibited in p56lck deficient but not in CD45 deficient mice. This suggests that CD45 is dispensable for beta-selection though p56lck is required.

Animals↗

PubMed1998

The role of gammadelta T cells in induction of bacterial antigen-specific protective CD8+ cytotoxic T cells in immune response against the intracellular bacteria Listeria monocytogenes.

The role of T-cell receptor (TCR) gammadelta T cells in the induction of protective TCR alphabeta T cells against infection by the intracellular bacteria Listeria monocytogenes was analysed. We found that depletion of gammadelta T cells by anti-TCR delta monoclonal antibody treatment before intravenous immunization of mice with a sublethal dose of viable L. monocytogenes resulted in reduction of protection against secondary challenge infection in the immunized mice. The gammadelta T-cell depletion also reduced induction of protective alphabeta T cells capable of transferring the protection against challenge infection of L. monocytogenes into naive mice. Furthermore, the protective T cells that were affected by the gammadelta T-cell depletion were suggested to be CD8+ cytotoxic T cells rather than CD4+ T cells by the following observations. First, induction of cytotoxic T lymphocytes specific to a L. monocytogenes-derived H-2Kd-restricted peptide (listeriolysin O 91-99) was significantly suppressed by gammadelta T-cell depletion before immunization. Second, gammadelta T-cell depletion did not affect cytokine production and proliferation of T cells from immunized mice in response to in vitro stimulation with heat-killed Listeria which preferentially stimulates CD4+ T cells. Third, CD8+ alphabeta T cells from control immunized mice transferred protection against infection of L. monocytogenes into naive mice but only a limited degree of protection was transferred by CD8+ T cells from the gammadelta T-cell-depleted immunized mice; and fourth, CD4+ alphabeta T cells from the gammadelta T-cell-depleted mice transferred a similar level of protection as those from the control immunized mice. All these results suggest that gammadelta T cells participate in establishment of protective immunity against intracellular bacteria by supporting priming of bacterial antigen-specific CD8+ cytotoxic T cells.

Adoptive Transfer↗

PubMed1998

Inhibition of corneal inflammation by the topical use of Ras farnesyltransferase inhibitors: selective inhibition of macrophage localization.

PURPOSE: Ras farnesyltransferase inhibitors are known to block the membrane translocalization of oncogenic Ras protein. They inhibit the cytoplasmic mitogen-activated protein kinase signaling cascade related to Ras protein. Thus far, Ras farnesyltransferase inhibitors have been exclusively regarded with the anticancer drugs. The object of this study was to elucidate the role of Ras farnesyltransferase inhibitors on the corneal opacity induced by an inflammatory stimulus. METHODS: We used a cauterization-induced corneal inflammation model. The central corneas of BALB/c mice were cauterized with silver nitrate (1 mm in diameter). Ras farnesyltransferase inhibitors, either manumycin or gliotoxin eye drops (each drug dissolved in balanced salt solution [BSS] at concentrations of 1 mM), were topically delivered to the cauterized cornea every 8 hours; BSS eye drops were used as a control. Clinical signs such as corneal edema, opacity, and corneal neovascularization, which are major causes of visual disturbance, were then examined 96 hours after the cauterization. The corneal edema and opacity were clinically scored under a stereoscopic microscope. The corneal neovascularization was evaluated by the length of the blood vessels from the limbus and the sum of extension central angle of vascularized limbus. Furthermore, the corneas were examined histologically, and the phenotypes of the cornea-infiltrating cells were analyzed by flow cytometry. RESULTS: The control corneas showed prominent edema, neovascularization, and opacity. Histologic analysis revealed corneal epithelial and endothelial cell loss and a large amount of inflammatory cell infiltration into the corneal stroma. Flow cytometric analysis revealed that most of the infiltrating cells were neutrophils and macrophages. In contrast, the degree of corneal edema, neovascularization, and opacity was significantly less in the manumycin- or gliotoxin-treated corneas than in the control corneas. Histologically, the manumycin- and gliotoxin-treated corneas showed minimum edema and good epithelialization. Flow cytometric analysis showed corneal infiltration of macrophages to be selectively and clearly inhibited. Neither manumycin nor gliotoxin produced any side effects in the noncauterized normal cornea either clinically or histologically. CONCLUSIONS: Ras proteins play an important role in cauterization-induced corneal inflammation and the opacity it induces. Ras farnesyltransferase inhibitors thus have a great potential for improving the treatment of corneal opacity induced by a corneal inflammatory stimulus.

Administration, Topical↗

PubMed1997

T cell development in mice expressing splice variants of the protein tyrosine phosphatase CD45.

The transmembrane protein tyrosine phosphatase CD45 is expressed in multiple isoforms as a result of alternative splicing of variable exons encoding the extracellular domain. CD45 expression is critical for T cell development, and thymocyte maturation is blocked at the immature CD4+ CD8+ double-positive stage in CD45 gene-deficient (CD45 -/-) mice. Moreover, splicing of variable CD45 exons changes during thymocyte selection. To test the role of CD45 extracellular splice variants in T cell selection and development, we introduced CD45RO (a low-m.w. splice variant lacking exons 4, 5, and 6) and CD45ABC (a high-m.w. isoform containing all exons) transgenes under the control of a thymocyte-specific promoter into a CD45 -/- background, generating CD45RO transgene-positive CD45 -/- (CD45RO) and CD45ABC transgene-positive CD45 -/- (CD45ABC) mice. We demonstrate that both CD45 splice isoforms can rescue development of CD4+ and CD8+ TCR-alphabeta+ thymocytes. Neither CD45 isoform rescued positive selection of H-Y TCR transgene thymocytes, and these cells were blocked at a HSA(high) CD69- CD5(low) stage of development. Peripheral T cells from CD45RO and CD45ABC mice proliferated in response to allogeneic stimulator cells and anti-CD3epsilon cross-linking. However, only CD45RO mice, not CD45ABC mice, generated cytotoxic T cell responses and neutralizing, Th cell-dependent IgG Abs after viral infections. In addition, we show that T cells from CD45RO and CD45ABC mice accumulate in lymph nodes but not in the spleen, liver, or skin, indicating that the CD45 phosphatase may control the homing behavior and trafficking of T cells.

Alternative Splicing↗

PubMed1997

Alterations in the level of CD45 surface expression affect the outcome of thymic selection.

CD45 is a receptor protein tyrosine phosphatase whose activity is required for thymocyte development and TCR-mediated signal transduction. Here we show that positive selection of TCR-alphabeta transgenic thymocytes is completely blocked in CD45 exon 6 -/- gene-deficient (CD45 -/-) mice that express the P14 TCR specific for the lymphocytic choriomeningitis virus. Thymocytes from mice heterozygous for the targeted disruption of the CD45 gene (CD45 +/-) displayed a reduction in both CD45 surface intensity and enzymatic CD45 protein tyrosine phosphatase activity. Surprisingly, positive thymocyte selection was enhanced in CD45 +/- mice as characterized by an up-regulation of the P14 TCR on thymocytes and increased numbers of transgenic T cells. Using a variant of lymphocytic choriomeningitis virus that is impaired in the induction of negative selection of P14 thymocytes, we also show that the reduction of CD45 surface expression in CD45 +/- mice rendered P14 transgene thymocytes susceptible to negative selection. These data demonstrate that changes in the expression level of the receptor protein tyrosine phosphatase CD45 can alter thymic selection.

Animals↗

PubMed1997

Molecular cloning and characterization of a novel human receptor protein tyrosine phosphatase gene, hPTP-J: down-regulation of gene expression by PMA and calcium ionophore in Jurkat T lymphoma cells.

A novel cDNA encoding a 1436 aa protein was cloned using a PCR system with degenerate primers. This new gene, hPTP-J, was found to encode a PTP protein consisting of an extracellular region containing an MAM (meprin, A5, mu)-like domain, an immunoglobulin-like domain, four fibronectin type-III repeats, a transmembrane region, and a cytoplasmic region containing two tandemly repeated PTP domains hPTP-J is thus considered to be a new member of the type II receptor PTP (RPTP) subfamily, like RPTP mu and RPTP kappa. hPTP-J gene expression was strongly detected in skeletal muscle and moderately detected in the prostate, pancreas, placenta, and heart, but was only weakly detected in the peripheral blood lymphocytes, thymus, and spleen even though gene expression was relatively high in the Jurkat T lymphoma cell line. Moreover, hPTP-J gene expression was down-regulated after Jurkat cells were stimulated by either PMA or calcium ionophore. Based on these findings, it is suggested that some signaling pathways mediated by PMA and/or intracellular calcium are involved in the regulation of hPTP-J gene expression in Jurkat cells.

Amino Acid Sequence↗

PubMed1997

Normal macrophage functions, but impaired induction of gamma delta T cells, at the site of bacterial infection in CD45 exon 6-deficient mice.

We investigated the protective functions of macrophages and gamma delta T cells in adult CD45 exon 6-deficient (CD45 -/-) mice against an intraperitoneal (i.p.) infection with Listeria monocytogenes. gamma delta T cells are preferentially localized in the spleen, liver, and intraperitoneal cavity of the adult CD45-/- mice. Increased numbers of gamma delta T cells were observed after i.p. infection with L. monocytogenes in the peritoneal cavity of C57BL/6 (CD45 +/+) mice but not in CD45 -/- mice. The gamma delta T cells showed predominant usage of V delta 5 and V delta 6 rearranged to J delta 1 in the infected CD45 -/- mice which are the same as those used by resident gamma delta T cells of noninfected CD45 +/+ and CD45 -/- mice. Furthermore, we analyzed the protective abilities of the CD45 -/-, CD45 +/+, and gamma delta T cell-depleted mice at the early stage of the listerial infection. The numbers of bacteria in the spleens and livers of the CD45 -/- mice 5 days after the listerial infection were almost ten times larger than those in the CD45 -/- and gamma delta T cell-depleted CD45 +/+ mice. Macrophages showed normal antigen presentation, nitric oxide production and bactericidal activity for L. monocytogenes despite their lacking CD45 surface expression, suggesting that CD45-negative macrophages have a minimal influence on the increased bacterial multiplication in the CD45-/- mice. These results suggest that the gamma delta T cells are induced by the bacterial infection in a CD45-dependent manner, and that unresponsiveness of the gamma delta T cells results in only weak protection against L. monocytogenes in CD45 -/- mice.

Animals↗

PubMed1997

Suppression of IgE production in mice treated with a traditional Chinese medicine, bu-zhong-yi-qi-tang (Japanese name: hochu-ekki-to).

The ability of a traditional herbal medicine, Bu-zhong-yi-qi-tang (Japanese name: Hochu-ekki-to, HOT), to suppress IgE production was investigated. BALB/c mice were intraperitoneally immunized with aluminium hydroxide adsorbed with DNP-KLH (DNP-KLH + alum). When oral administration of HOT was begun just after immunization, the serum level of antigen-specific IgE was significantly decreased, although those of antigen-specific IgG1 and IgG2a were not influenced. In the culture of spleen cells obtained 14 days after immunization with DNP-KLH, antigen-specific IgE and IgG1 production by the cells of the HOT-treated mice was significantly suppressed compared to that in immunized mice. Furthermore, in the combination culture with CD4+ T cells and B cells separated from spleen cells, IgE production by the cells from immunized mice was inhibited by replacement of their corresponding cell population with either CD4+ T cells or B cells of HOT-treated mice. Additionally, production of interleukin 2 (IL-2) and IL-4 was significantly suppressed in HOT-treated mice but not that of IFN-gamma in comparison to the immunized mice. These results suggested that HOT decreased the IgE level in serum by inhibiting the development of IL-4-producing CD4+ T cells.

Alum Compounds↗

PubMed1997

Restraint stress-induced elevation of endogenous glucocorticoid suppresses migration of granulocytes and macrophages to an inflammatory locus.

It has been reported that restraint stress gives rise to various immunosuppressive events. In the present study, we focused our interest on an early stage of the host-defense system in which granulocytes, macrophages and natural killer (NK) cells are involved. We observed that an elevation of endogenous glucocorticoid levels in mice induced by 24 h-restraint stress (acute stress) did not significantly reduce the NK activity of the spleen cells but profoundly suppressed the migration of macrophages and granulocytes into peritoneal cavities of the mice at 24 h after an intraperitoneal injection of proteose peptone. The reduced number of the migrated granulocytes and macrophages corresponded to a down-regulated gene expression of such chemotactic factors as MCP-1/JE in the peritoneal exudate cells of the stress-loaded mice. The stress-loaded mice recovered from such a suppressive state upon treatment with the glucocorticoid antagonist, RU-486, or upon adrenalectomy, suggesting that the elevated level of endogenous glucocorticoid is responsible for these suppressive effects of acute stress.

Adrenalectomy↗

PubMed1997

TCR alpha beta+ CD4- CD8- T cells differentiate extrathymically in an lck-independent manner and participate in early response against Listeria monocytogenes infection through interferon-gamma production.

T-cell receptor (TCR) alpha beta+ CD4- CD8- (double-negative; DN) T cells appear in the peritoneal cavity at an early stage of intraperitoneal (i.p.) infection with the intracellular pathogen Listeria monocytogenes. In the present report, we analysed the developmental pathway and functions of the TCR alpha beta+ DN T cells using the L. monocytogenes infection system. The TCR alpha beta+ DN T cells appeared in the peritoneal cavity after L. monocytogenes i.p. infection in adult-thymectomized lethally irradiated bone marrow chimeras and p56lck-deficient mice. The results demonstrated that the TCR alpha beta+ DN T cells can develop extrathymically in a p56lck-independent manner. Reverse transcription-polymerase chain reaction (RT-PCR) analysis showed that the TCR alpha beta+ DN T cells expressed genes for interferon-gamma (IFN-gamma), the macrophage chemotactic factors MCP-1 and Eta-1, and granulocyte-macrophage colony-stimulating factor (GM-CSF) but lacked expression of genes for interleukin-2 (IL-2), IL-4 and IL-10. As expected from the RT-PCR analysis, the TCR alpha beta+ DN T cells produced IFN-gamma in response to anti-TCR beta monoclonal antibody (mAb), anti-CD3 mAb and L. monocytogenes-infected macrophages but IL-4 was undetectable after the stimulation. Furthermore, the intracellular cytokine staining analysis demonstrated that approximately half of the TCR alpha beta+ DN T cells detectable at the early stage of L. monocytogenes infection were IFN-gamma-producing cells. All of the results suggest that the TCR alpha beta+ DN T cells develop through a unique extrathymic p56lck-independent pathway and participate in early protection against bacterial infection through activation and accumulation of macrophages.

Animals↗

PubMed1997

p56lck is not essential for the T-cell response to allo-MHC antigens.

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 lck -/- 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)-2R alpha+ 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 somewhat 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.

Animals↗

PubMed1996

Extrathymic development of self-reactive gamma(delta) T cells in athymic BALB/c nu/nu mice.

In the present report, we demonstrated that extrathymic gamma(delta) T cells proliferated in the mixed culture of lymph node cells of BALB/c nu/nu mice and irradiated syngeneic spleen cells (syngeneic MLR). Reverse transcription-polymerase chain reaction (RT-PCR) analyses revealed that V(delta)5 and V(delta)6 were dominantly expressed by the gamma(delta) T cells from the syngeneic MLR. Furthermore, the syngeneic MLR may expand V(delta)5+ T cells with BALB invariant delta (BID) sequence which is specifically detected in BALB background mice because V(delta)5 RT-PCR products from syngeneic MLR were digested with an AluI restriction enzyme which cut the D(delta)2-J(delta)1 junction of the BID sequence but not those of most non-BID V(delta)5 sequences. Interestingly, anti-mycobacterial and mammalian heat shock protein (Hsp) 60 mAb ML30 suppressed the generation of V(delta)5 with an AluI site in syngeneic MLR. These results suggest that extrathymically derived V(delta)5+ and V(delta)6+ gamma(delta) T cells recognize BALB/c self antigens and that the Hsp60 or an Hsp60-related molecule may be involved in the anti-self response of V(delta)5+ BID+ gamma(delta) T cells.

Animals↗

PubMed1996

Enhanced generation of NK cells with intact cytotoxic function in CD45 exon 6-deficient mice.

CD45 is a cell membrane-type protein tyrosine phosphatase that is essential for Ag receptor-mediated signaling in both T and B lymphocytes. To characterize roles of CD45 molecules in murine NK cells, we analyzed the development and the cytotoxic functions of NK cells in mice lacking CD45 exon 6 (CD45 -/-). A markedly increased number of NK cells was observed in spleens of the CD45 -/- mice, despite no CD45 surface expression on the NK cells. From the results of mixed bone marrow chimera experiments, it was demonstrated that the expansion of NK cells in CD45 -/- mice was due to the influence of disappeared expression of CD45 in the NK cells per se, but not to the modulation of environmental factors. The NK cells in the CD45 -/- mice had normal cytotoxic activities, including NK and Ab-dependent cell-mediated cytotoxicity activities comparable with those in normal mice (CD45 +/+). Additionally, the CD45 -/- NK cells could functionally differentiate to lymphokine-activated killer cells by culturing with a high dose of IL-2, despite a lack of induced expression of B220. Therefore, these results suggest that CD45 is involved in NK cell development, but is not essential for cytotoxic activities and Fc gamma R-mediated signaling in NK cells.

Animals↗

PubMed1996

The role of p56lck in the development of gamma delta T cells and their function during an infection by Listeria monocytogenes.

We investigated roles of p56lck tyrosine kinase (Lck) on the development and function of gamma delta T cells in adult mice using lck gene knockout (lck -/-) mice. The mature gamma delta T cells (heat-stable Ag negative) were generated significantly in the thymi of adult lck -/- mice. When Listeria monocytogenes was infected i.p., gamma delta T cells were induced in the peritoneal cavity of the lck -/- mice. Interestingly, the repertoire of gamma delta T cells was obviously different in the lck +/+ and lck -/- mice; i.e., the gamma delta T cells of the lck -/- mice induced by the listerial infection dominantly expressed V delta 1 while those of the lck +/+ mice dominantly expressed V delta 6. The V delta 1 + gamma delta T cells in the lck -/- mice were extrathymically generated, supported by their appearance in thymectomized irradiated mice reconstituted with bone marrow cells from the lck -/- mice. Furthermore, the gamma delta T cells of the lck +/+ mice were protective in the early stage of the listerial infection, while the gamma delta T cells in the lck -/- mice were not protective against the listerial infection because the depletion of the gamma delta T cells from the lck -/- mice did not influence the bacterial burden in the spleens. These observations thus suggest that 1) gamma delta T cells can develop in adult mice through the intrathymic and extrathymic pathways even in the absence of Lck, 2) Lck influences the expansion and the repertoire of gamma delta T cells, and 3) the gamma delta T cells raised in the absence of Lck are not protective against L. monocytogenes.

Animals↗

PubMed1996

Regulation of B-lymphocyte negative and positive selection by tyrosine phosphatase CD45.

Elimination of self-reactive B cells must be balanced against the need for B-cell diversity for antibody responses to pathogens. To analyse factors that determine the extent of B-cell negative selection, we crossed CD45-deficient mice with mice carrying immunoglobulin transgenes specific for hen egg lysozyme (HEL). CD45 positively regulates antigen-receptor signalling and CD45-deficient HEL-specific B cells gave diminished signalling in response to HEL. Significantly, few mature CD45-/- B cells accumulated, despite normal immature B-cell production. Circulating HEL autoantigen mediates negative selection of mature CD45+/+ HEL-binding B cells but, in striking contrast, the autoantigen positively selected CD45-/- HEL-binding B cells, promoting their accumulation as long-lived IgD(hi) cells. These findings are consistent with a signal-threshold model for B-cell selection and demonstrate that changes in antigen receptor signalling can cause high-affinity self-reactive B cells to be actively retained instead of eliminated, thus revealing a potential mechanism for inherited susceptibility to autoimmune disease.

Animals↗