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Early immune responses are important in shaping long-term outcomes of human lung transplants. To examine the role of early immune responses in lung rejection and acceptance, we developed a method to retransplant mouse lungs. Retransplantation into T-cell-deficient hosts showed that for lungs and hearts alloimmune responses occurring within 72 h of transplantation are reversible. In contrast to hearts, a 72-h period of immunosuppression with costimulation blockade in primary allogeneic recipients suffices to prevent rejection of lungs upon retransplantation into untreated allogeneic hosts. Long-term lung acceptance is associated with induction of bronchus-associated lymphoid tissue, where Foxp3(+) cells accumulate and recipient T cells interact with CD11c(+) dendritic cells. Acceptance of retransplanted lung allografts is abrogated by treatment of immunosuppressed primary recipients with anti-CD25 antibodies. Thus, events contributing to lung transplant acceptance are established early in the graft and induction of bronchus-associated lymphoid tissue can be associated with an immune quiescent state.

Sphingosine 1-phosphate (S1P) and its receptor, S1P receptor type 1 (S1P(1)), are essential for lymphocyte egress from secondary lymphoid organs (SLO). Fingolimod (FTY720), the S1P receptor modulator, inhibits lymphocyte egress from SLO and decreases circulating lymphocytes; however, it also induces a significant decrease in the number of peripheral blood lymphocytes in alymphoplasia (aly/aly) mice lacking SLO. In this study, we demonstrated that the administration of FTY720 induced sequestration of mature lymphocytes, particularly T cells, into the bone marrow (BM) in aly/aly mice, implying that the reduction of circulating lymphocytes in these mice by FTY720 was due to inhibition of lymphocyte egress from the BM. Since sequestration of mature T cells into the BM was also induced in normal mice by selective S1P(1) agonist or S1P lyase inhibitor, it is suggested that S1P(1) expression and the S1P gradient play an important role in egress of mature T cells from the BM. Prophylactic administration of FTY720 to ovalbumin (OVA)-immunized mice significantly inhibited footpad swelling induced by OVA challenging with a marked reduction of OVA-specific T(h) cells in the BM, indicating that immunomodulation by FTY720 is likely due to reduced circulation of antigen-specific T(h) cells. On the other hand, OVA-specific T(h) cells, like naive T cells, were also sequestered into the BM and SLO of OVA-immunized mice by a short exposure of FTY720 after OVA challenging. These results suggest that the S1P-S1P(1) axis plays a regulatory role in egress of mature T cells including antigen-specific T(h) cells from the BM.

The expression pattern and distribution of proteasome immune subunits LMP7 and LMP2 in the developing rat spleen and liver as well as the periarterial lymphoid sheath formation were investigated. LMP7 and LMP2 were detected by immunoblotting in the spleen on the 21st embryonic day and during the first postnatal days in equal amounts. Their levels increased by the 8th and 18th postnatal days. Double immunofluorescent labeling the spleen cells revealed LMP7 and LMP2 in T and B lymphocytes localized in the red pulp in embryogenesis. Few T lymphocytes were discovered in periarterial zones on the 8th postnatal day. T lymphocytes filled these zones and formed lymphoid sheaths by the 18-19th day. In the liver, LMP7 and LMP2 were revealed by the 17-19th postnatal day. Immunofluorescent analysis showed their presence in hepatocytes at this period. The data suggest that T cell-mediated immune response in relation to hepatocytes is possible beginning from 18th to 19th postnatal day.

The effect of the larger molecular weight l-amino acids on the development of spleen explants from 1- and 21-day rats in organotypic tissue culture was studied. The amino acids asparagine, lysine, arginine, and glutamic acid inhibited the growth zone of explants of immature tissue from 1-day animals but had an opposite, stimulating, effect on mature spleen tissue of 21-day rats. Immunohistochemical analysis revealed a reciprocal correlation between the expression of the proapoptotic protein, p53, and T-cell proliferation in response to lysine, asparagine, and glutamic acid. Interestingly only arginine reduced the area of p53 expression both in explants of mature and immature spleen tissue. The ability of arginine to reduce p53 expression can be suggested as one of the mechanisms of the tumor growth stimulation.

The prevalence of allergic diseases has risen markedly since the 1960s, particularly in the developed countries of the Western world. These diseases manifest initially during infancy and childhood and are apparently becoming more persistent in successive birth cohorts. The importance of genetic susceptibility in the disease process is widely recognized, and it is further recognized that the ultimate expression of the disease is the result of complex interactions between genetic and environmental factors, with nutrition representing 1 main variable, neither of which have yet been comprehensively characterized. There is increasing evidence that the level of complexity inherent in the pathogenesis of allergic diseases may be even greater than is currently contemplated, as an additional set of crucial factors appear to be involved. Notably, it appears likely that the ultimate effects of the "gene-environment" interaction within individuals may also be related to the developmental status of the relevant target tissues at the time the interactions occur. Examples of the latter, discussed below, are elements of innate and adaptive immune function and aspects of food allergy and of airway function relevant to atopic asthma.

Adaptive immunity is crucial for protective host defense and the development of immunological disorders. SLY1 was recently identified as an X-chromosomal SH3 protein that is serine phosphorylated (Ser27) upon B-and T-cell receptor engagement. Here, we demonstrate that SLY1 is localized in the cytoplasm and the nucleus of immunocytes. We generated mice expressing a mutant version of SLY1 lacking Ser27 and a functional nuclear localization signal. The defective SLY1 (SLY1(d)) protein is localized exclusively in the cytoplasm. B- and T-cell proliferation is attenuated and T-cell cytokine production is severely reduced. Sly1(d/d) mice exhibit reduced lymphoid organ sizes, diminished marginal zone B-cell numbers, and severely impaired antibody responses against T-dependent and -independent antigens. Importantly, survival of semi-identical cardiac allografts was substantially prolonged in Sly1(d/d) mice. These results define SLY1 as an essential molecular component for the full activation of adaptive immunity.

An experiment was conducted, including flow cytometry, to study the pathology of the lymphoid organs and peripheral blood T lymphocytes in zinc (Zn)-deficient chickens. One hundred 1-day-old broiler chickens were randomly divided into two groups and fed on diets with 100 mg/kg Zn (controls) or Zn-deficient diets (Zn, 23.63 mg/kg) for 7 weeks. The weight and growth index of the bursa of Fabricius, thymus and spleen were significantly reduced (P<0.05 or P<0.01) in Zn-deficient birds when compared with those of control broilers. The G0/G1 phase of the cell cycle of the bursa, thymus and spleen was much higher (P<0.01), and the S, G2+M phases and proliferating index lower (P<0.05 or P<0.01) in Zn-deficient broilers than in the controls. The acid alpha-naphthyl acetate esterase-positive ratio of the peripheral blood T lymphocytes and the CD4 and CD8 numbers were markedly reduced (P<0.05 or P<0.01), and the CD4/CD8 ratio increased. Histopathologically, lymphocytes of lymphoid organs were depleted and the reticular cells of the thymus were also degenerate or necrotic in the Zn-deficient birds. The results demonstrate that Zn deficiency seriously inhibited the development of lymphoid organs, impaired the progression of lymphocytes from the G0/G1 phase to the S phase, and caused pathological injury in the lymphoid organs. The results also showed that the effect of Zn deficiency on the primary lymphoid organs occurred earlier than on the secondary lymphoid organs. The effect of Zn deficiency was greatest on the bursa of Fabricius, followed by the thymus, and then the spleen. Potential mechanisms underlying the observations are discussed.

This paper describes the initial appearance and distribution of mature T and B cells in the developing immune tissues of the stripe-faced dunnart (Sminthopsis macroura) based on the use of species cross-reactive antibodies to the lymphocyte cell surface markers CD3, CD5 and CD79b. At birth no mature T or B cells were detected in the liver or bone marrow using anti-CD3, anti-CD5 or anti-CD79b antibodies. T cells were detected in the thymus with anti-CD3 by day 12 and anti-CD5 by day 50 postpartum, and T cells in the spleen were detected by day 43 and day 80 postpartum using anti-CD3 and anti-CD5, respectively. B cells were observed in the dunnart spleen by 43 days after birth. CD3- and CD79b-positive cells were detected in the lymph nodes by 50 days and CD5 by day 15 after birth, and in the gut-associated lymphoid tissues by day 50 and anti-CD5 by day 57 postpartum. The development and distribution of T and B cells in the immune tissues of dunnart pouch young is similar to that described in other marsupial species. Low numbers or absence of mature lymphocytes in immune tissues of early pouch young dunnarts further support the proposition that young marsupials are reliant on non-specific defence strategies and/or maternal strategies for a significant period of their time of development in the pouch.

The distribution of T- and B-cells in the developing lymphoid and immunohaematopoietic tissues of the tammar wallaby were investigated using antibodies to the mature cell surface markers, CD3, CD5 and CD79b. In the thymus, CD3- and CD5-positive T-cells were first observed at day 12 postpartum whilst rare B-cells were first detected at day 23. Both T- and B-lymphocytes were first stained on day 21 postpartum in the spleen and day 24 in lymph nodes. In one sample from a 7-day-old animal, rare CD79b-positive (CD79b+) lymphocytes were observed in the gut-associated lymphoid tissues. However, CD3+ cells were not apparent until day 12 and CD5+ cells were not detected until day 74 postpartum. No lymphocytes were detected in liver or bone marrow samples and no bronchus-associated lymphoid tissues were observed. The pattern of development and the distribution of T- and B-cells in the lymphoid and immunohaematopoietic tissues were similar to those observed in eutherian mammals and in limited studies of other metatherians. However, the detection of apparently mature T- and B-cells in the thymus and gut-associated lymphoid tissues (GALT) at the same postnatal age highlights the need for a more substantial study of the development of GALT. This is, at present, limited by availability of marsupial-specific antibodies.

The tetraspanins are a family of integral membrane proteins with four transmembrane domains. These molecules form multimolecular networks on the surfaces of many different cell types. Gene-targeting studies have revealed a role for tetraspanins in B- and T-lymphocyte function. We have isolated and deleted a novel tetraspanin, Tssc6, which is expressed exclusively in hematopoietic and lymphoid organs. Using a gene-trapping strategy, we generated an embryonic stem (ES) cell line with an insertion in the Tssc6 locus. Mice were derived from these ES cells and, using RNase protection and reverse transcription-PCR, we demonstrated that the insertion resulted in a null mutation of the Tssc6 allele. Mice homozygous for the gene trap insertion (Tssc6(gt/gt) mice) were viable and fertile, with normal steady-state hematopoiesis. Furthermore, responses to hemolysis and granulocyte colony-stimulating factor-induced granulopoiesis were equivalent to those of wild-type mice. Lymphoid development was normal in Tssc6(gt/gt) mice. Whereas Tssc6(gt/gt) B cells responded normally to lipopolysaccharide, anti-CD40, and anti-immunoglobulin M stimulation, Tssc6(gt/gt) T cells showed enhanced responses to concanavalin A, anti-CD3, and anti-CD28. This increased proliferation by Tssc6-deleted T lymphocytes was due to increased interleukin 2 production following T-cell receptor stimulation. These results demonstrate that Tssc6 is not required for normal development of the hematopoietic system but may play a role in the negative regulation of peripheral T-lymphocyte proliferation.

Previous studies have analyzed the lymphoid and myeloid foci within the gingival mucosa in health and chronic periodontitis (CP); however, the principal APCs responsible for the formation and organizational structure of these foci in CP have not been defined. We show that in human CP tissues, CD1a(+) immature Langerhans cells predominantly infiltrate the gingival epithelium, whereas CD83(+) mature dendritic cells (DCs) specifically infiltrate the CD4(+) lymphoid-rich lamina propria. In vivo evidence shows that exacerbation of CP results in increased levels of proinflammatory cytokines that mediate DC activation/maturation, but also of counterregulatory cytokines that may prevent a Th-polarized response. Consistently, in vitro-generated monocyte-derived DCs pulsed with Porphyromonas gingivalis strain 381 or its LPS undergo maturation, up-regulate accessory molecules, and release proinflammatory (IL-1beta, PGE(2)) and Th (IL-10, IL-12) cytokines. Interestingly, the IL-10:IL-12 ratio elicited from P. gingivalis-pulsed DCs was 3-fold higher than that from Escherichia coli-pulsed DCs. This may account for the significantly (p < 0.05) lower proliferation of autologous CD4(+) T cells and reduced release of IFN-gamma elicited by P. gingivalis-pulsed DCs. Taken together, these findings suggest a previously unreported mechanism for the pathophysiology of CP, involving the activation and in situ maturation of DCs by the oral pathogen P. gingivalis, leading to release of counterregulatory cytokines and the formation of T cell-DC foci.

Proviral activation of the Bmi1 gene has implicated Bmi1 as a collaborator of c-Myc in lymphomagenesis. To determine the effect of Bmi1 overexpression on hematopoiesis and lymphomagenesis transgenic mice were generated that overexpress different forms of the Bmi1 protein in their lymphoid compartment. Emu Bmi1 transgenic mice, overexpressing the wild type Bmi1 protein showed a perturbed lymphoid development and were highly susceptible to B and T cell lymphomagenesis. Mutational analysis of the Bmi1 protein demonstrated that the conserved N-terminal RING finger and central part of Bmi1 are essential for its oncogenic potential whereas the C-terminal Pro-Ser rich region is not required. We have used provirus tagging in the Emu Bmi1 mice to identify genes that cooperate with Bmi1 in lymphomagenesis. MoMLV infection in Emu Bmi1 transgenic mice accelerated lymphoma development. Proviral activation of the Pim and Myc genes but not the Gfi1 gene were frequently observed in these tumors. These results demonstrate that Bmi1 is a potent oncogene and suggest that it plays an important role in early lymphoid development.

HS1, an intracellular protein expressed specifically in hematopoietic cells, is rapidly tyrosine phosphorylated after cross-linking of antigen receptors on B and T lymphocytes, implicating involvement of this molecule in the signal transduction pathways from the antigen receptors as a substrate of membrane-associated tyrosine kinase(s). The development of lymphoid cells in HS1-deficient mice, generated through gene targeting, appeared normal. However, antibody production to T-independent antigen and proliferative responses of splenic B and T cells after cross-linking of the antigen receptors were impaired in these mutant mice. Furthermore, B cells in the peritoneal cavity of the mutant mice were resistant to multivalent cross-linking of the antigen receptor, which causes apoptosis of such cells in normal mice. Crossing the HS1-deficient mice with the mice harboring transgenes encoding alpha and beta chains of T-cell antigen receptor against a male H-Y antigen resulted in a progeny that demonstrated a significantly impaired ability of thymic negative selection. These results indicate that HS1 is a novel molecule involved in the antigen-receptor-derived signaling pathways and plays important roles not only in clonal expansion, but also in clonal deletion of B and T cells.

The intestinal lymphoid compartment has a rather stable composition throughout life. However, both during early neonatal development and at high age unique cell populations can be recognized at distinct sites in the intestinal tissue. Directly after birth all intestinal CD3+ cells are found in the lamina propria. At this time the epithelium does not contain T cells. These CD3+ lamina propria lymphocytes co-express both TCR beta and TCR delta chains, probably reflecting the expression of a TCR beta delta heterodimer on the cell surface. Cells with this particular phenotype are present in comparable numbers in the lamina propria of both neonatal euthymic and athymic mice, indicating the thymus-independent nature of these cells. During aging the frequency of TCR alpha beta+ CD8 alpha alpha+ intestinal T cells increases. These cells are also considered to be thymus-independent. The appearance of high numbers of CD4+ CD8 alpha alpha+ intestinal T cells in aged mice is even more striking. It is postulated that the neonatal TCR beta delta+ cells, and probably also the CD4+ CD8 alpha alpha+ cells as found in old mice, are intermediates in the extrathymic differentiation pathway of TCR alpha beta+ CD8 alpha alpha+ intestinal T cells.

We assessed the kinetics of V beta 6+ T cell elimination in the lymph nodes and thymus during Mls-1a mouse ontogeny. Our results suggest that induction of tolerance to Mls-1a antigens involves mechanisms other than clonal deletion of immature T cells in the thymus. Mature CD4+CD8- (CD4SP) T cells were affected by Mls-1a antigens earlier than immature thymocyte populations. Up to 2 weeks after birth, reduced frequencies of V beta 6+ T cells were detected only in CD4SP cells from the thymus and lymph nodes, and generation of CD4SP cells in the thymus was blocked at least 1 week earlier than that of their CD4+CD8loTCRhi immature precursors. The number of V beta 6+CD4SP T cells increased during the first 2 weeks of life and remained constant thereafter. We thus found no evidence of deletion of mature V beta 6+CD4SP T cells, as the reduced frequencies in adult mice can be attributed to the dilution of previously generated cells in lymphoid organs of growing mice, which increase in cellularity after birth. V beta 6+CD4+ T cells were activated in vivo shortly after birth, as shown by a selective increase in IL-2 receptor alpha chain expression in the thymus and lymph nodes from day 0 to day 2 after birth. It is therefore likely that endogenous expression of Mls-1a antigen shortly after birth activates V beta 6+CD4SP T cells and renders them anergic. This process of tolerance induction may precede the clonal deletion of immature T cells in the thymus, described in the adult mouse.

To evaluate the biologic potential of T cell-specific TNF production in vivo, we have generated transgenic mice constitutively expressing TNF in their T cell compartment. This was achieved by placing a wild-type or a 3'-UTR modified fragment of the human TNF gene under the influence of the T cell-specific, locus control region of the human CD2 gene. Transgenic mice that express human TNF mRNA in T cells develop marked histologic and cellular changes locally in their lymphoid organs and a lethal wasting syndrome associated with widespread vascular thrombosis and tissue necrosis. The extent of pathologic changes and their time of onset appear to reflect levels of transgene expression. Thus, transgenic lines that express the transgene at high levels show both lymphoid organ and systemic abnormalities with wasting. In one transgenic line, mice express lower levels of the transgene and develop normally despite pronounced local lymphoid organ defects, confirming in vivo, the differential potential of localized and systemic TNF action. All pathologic changes could be neutralized by the administration of mAb specific for human TNF. These results demonstrate the important role of T cell-specific TNF production in the development of specific pathology and provide a means by which to evaluate the role of TNF in thymocyte development. Transgenic mice that express TNF constitutively in the T cell compartment offer a unique in vivo system by which to analyze the molecular character of systemic vs contact-dependent and paracrine modes of TNF action. Furthermore, given the species-specific nature of the mouse p75 TNF receptor, it is assumed that the pathology induced by human TNF in these transgenic mice is associated exclusively with p55 TNF receptor signaling. Conceivably, the differential contribution of each of the two TNF receptors in thymus development and TNF-mediated disease can be assessed by comparison of the biologic potential of human vs mouse TNF in the transgenic system developed.

Vertebrate T cells express either an alpha beta or gamma delta T cell receptor (TCR). The developmental relatedness of the two cell types is unresolved. alpha beta + T cells respond to specific pathogens by collaborating with immunoglobulin-producing B cells in distinct lymphoid organs such as the spleen and Peyer's patches. The precise influence of alpha beta + T cells on B cell development is poorly understood. To investigate the developmental effects of alpha beta + T cells on B cells and gamma delta + T cells, mice homozygous for a disrupted TCR alpha gene were generated. The homozygotes showed elimination of alpha beta + T cells and the loss of thymic medullae. Despite this, gamma delta + T cells developed in normal numbers, and there was an increase in splenic B cells.

The development of bronchus associated lymphoid tissue was studied in normal rats, in serial sections, using both routine histological techniques and the two-step immuno-peroxidase method on cryostat sections for demonstration of T lymphocytes, IgM-, IgG- and IgA-bearing B lymphocytes and plasma cells, respectively. BALT first appears 4 days postpartum (p.p.) as a condensation of reticulum cells near a lymph vessel, between the main bronchus and the accompanying artery. Only a few lymphocytes are present at first. Vascularisation is considerable 8 days p.p. and includes high endothelial venules. Leucocytes are seen in transit in both blood- and lymph vessel walls. Lymphocytes populate the area under the epithelium from about 2 weeks p.p. A few IgM, IgG- and IgA-bearing B cells are already present at 4 days, and rapidly increase in numbers; T cells usually appear at day 8. Discrete T- and B-cell areas do not appear until 4 weeks and are only observed regularly after 12 weeks, when secondary follicles appear. BALT starts development at a similar time to other peripheral lymphoid organs but apparently achieves immunological activity later. It is concluded that antigens probably play an important part in organising BALT.

Rats of the BB strain develop diabetes mellitus in a high percentage and display a severe T-cell lymphopenia. In order to investigate the role of micro-environmental factors in the T-cell maturation in BB rats the postnatal development of macrophage subpopulations and T-lymphocyte subsets, in addition to the specific immune response in situ, were studied in thymus, spleen and lymph nodes of BB rats. Wistar rats were used as controls. From the day of birth on, a severe reduction was noticed in the macrophage subpopulations in the thymic cortex of BB rats, but not in spleen and lymph nodes, as compared to Wistar rats. The population of T-suppressor/cytotoxic cells (OX8-positive cells) did not increase any longer from Day 10 after birth in the thymic cortex and from Day 14 in spleen and lymph nodes. This is indicative for an intrathymic maturational defect of the OX8-positive cells in BB rats. No deviations could be observed in the development of the T-helper (ER2-positive) cell population. Young adult BB rats were as capable as Wistars of developing a specific immune response to thymus-independent (TI) antigens, but the response to a thymus-dependent (TD) antigen was delayed and decreased. Also the distribution pattern of the specific antibody-containing cells in a TD response in BB rats differed from that in Wistar rats. The ER2-positive cells, although present in normal numbers, may function insufficiently as T-helper cells in BB rats.

Interleukin-2 (IL-2) generates T lineage cell lines (IL-3B series) directly from the isolated interleukin 3 (IL-3)-induced pluripotential progenitor colonies obtained form adult spleen in vitro. The phenomenon can be reproduced by the combined IL-3/IL-2 bulk culture system. In order to compare the differentiation potential of such progenitors in various ontogenical stages, we have established a number of cell lines from fetal livers (LFD series), fetal thymus (FTD15), newborn spleens (SED series), and adult spleens (SPB series) using the IL-3/IL-2 culture system. The phenotypes of cell lines varied depending upon the developmental stages; LFD lines, Thy1+CD3-CD4-CD8-B220+, FTD15, Thy1+CD3+CD4-CD8+B220-, and SPB and IL-3B lines, Thy1+CD3+CD4-CD8+B220+. Analysis of T cell receptor (TCR) genes revealed that all of the TCR genes (alpha, beta, gamma, and delta) were in germ line configurations in LFD lines. In LFD17 and 19, from 17 and 19 gestation days (GD) respectively, however, germ line transcripts or TCR beta gene were detected, suggesting that they were in the earliest phase of T cell commitment. In LFD14 line from GD14 fetal liver, no such transcript could be detected. In contrast, FTD15 showed complete rearrangement of every TCR gene with full-length TCR alpha and beta gene mRNA. On the other hand, all of the SED, SPB, and IL-3B series of lines exhibited the rearrangement of every TCR gene with productive TCR alpha and beta gene mRNA. The results indicated that progenitors in postnatal spleen, in contrast to those in fetal liver, had the potential to rearrange and express the TCR genes in extrathymic conditions in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

The monoclonal antibody anti-Tac, which binds to the interleukin 2 (IL 2) receptor, was used to identify this antigen in human fetal and adult lymphoid tissue. Liver, spleen, thymus, lymph node, and peripheral blood were examined for Tac-positive cells with the use of frozen sections or cytocentrifuge preparations. The results show that cells in the fetal and neonatal thymus express the Tac antigen; these cells are predominantly located in the medulla. The liver and spleen of both fetus and adult exhibit very few Tac-positive cells. Double staining demonstrates that cells bearing the Tac-antigen stain with Leu-4, an anti-T cell antibody. In adult lymph node tissue, the Tac-bearing cells are predominantly distributed in the interfollicular area, with positive cells also present in the germinal center and mantle zone. The Tac antigen is present on both T and B cells. Few Tac-positive cells are present in the circulating peripheral blood.