Lymphotoxin plays a crucial role in the development and function of nasal-associated lymphoid tissue through regulation of chemokines and peripheral node addressin

The mechanism of nasal-associated lymphoid tissue (NALT) development is incompletely understood with regard to the roles of cytokines, chemokines, and vascular addressins. Development of the wild-type NALT continued in the immediate postnatal period with gradual increases in cellularity, compartmentalization into T- and B-cell zones, and expression of lymphotoxin (LT)-alpha, LT-beta, and lymphoid chemokines (CCL21, CCL19, CXCL13). High endothelial venules (HEVs) developed that expressed GlyCAM-1, HEC-6ST [an enzyme crucial for expression of luminal peripheral node addressin (PNAd)], and PNAd itself. LT-beta(-/-) and LT-alpha(-/-) NALTs had fewer cells than those of wild-type mice, reduced (LT-beta(-/-)) or absent (LT-alpha(-/-)) lymphoid chemokines, and no T- and B-cell compartmentalization. LT-beta(-/-) HEVs expressed only abluminal PNAd and no HEC-6ST or GlyCAM-1. LT-alpha(-/-) HEVs had no PNAd, HEC-6ST, or GlyCAM-1. Because intranasal immunization gives rise to vaginal IgA, immunization of LT-beta(-/-) mice, which retain cervical lymph nodes, might generate such a response. Intranasal immunization with ovalbumin and cholera toxin revealed lower cytokine levels in the LT-alpha(-/-) and LT-beta(-/-) NALTs, and undetectable vaginal IgA. In contrast, splenic cytokines and serum IgG titers, although reduced, were detectable. These data indicate that LT-alpha(3) and LT-alpha(1)beta(2) cooperatively contribute to NALT development and function through regulation of lymphoid chemokines and adhesion molecules; they are the first to implicate LT-alpha(1)beta(2) in GlyCAM-1 regulation in NALT HEV development.     

Membrane lymphotoxin is required for resistance to Theiler's virus infection

Lymphotoxin (LT) and tumor necrosis factor (TNF) are important in immune system development and function. LT consists of soluble LT-alpha(3), which binds to TNF-R1 and TNF-R2, and membrane LT-alpha(1)beta(2), which binds to LT-beta-R. We investigated the role of LT and TNF in disease induced by Daniel's (DA) strain of Theiler's murine encephalomyelitis virus (TMEV) since the immune response is believed to be important in both resistance to DA infection as well as mediation of virus-induced demyelination. DA persisted and induced inflammatory demyelination in LT-alpha(-/-) (but not TNF(-/-)) weanling mice of a normally resistant haplotype (C57BL/6), suggesting that LT, but not TNF, is critical for resistance to DA infection. This activity of LT depends on membrane LT-alpha(1)beta(2) and not soluble LT-alpha(3), since DA virus persisted and induced inflammatory demyelination in LT-beta-R(-/-), but not TNF-R1(-/-) or TNF-R2(-/-), mice. The LT-alpha(-/-) and LT-beta-R(-/-) mice failed to mount a virus-specific cytotoxic T cell response. Treatment of weanling C57BL/6 mice with LT-beta-R-Ig, which blocks membrane LT activity, failed to increase susceptibility, suggesting that the LT effect is related to its action on immune system development which is fixed by 3 weeks of age. Our data suggest that membrane LT is important in resistance to DA infection (possibly through interference with CD8+ T cell development and function). There was relatively little demyelination associated with inflammation in LT-alpha(-/-) and LT-beta-R(-/-) mice compared to susceptible SJL mice, suggesting the possibility that LT plays a role in mediating demyelination.     

Expression of lymphotoxin-beta (LT-beta) in chronic inflammatory conditions

Functional studies in gene-knockout and transgenic mice systems have shown that lymphotoxin-alpha and lymphotoxin-beta (LT-alpha and LT-beta) are of fundamental importance in peripheral lymphoid organ development, but it remains unclear what role these cytokines have to play in the adult immune response and in the pathogenesis of disease. In this study, a polyclonal anti-serum to human LT-beta was used to investigate the distribution of LT-beta by immunohistochemistry in normal and diseased tissues. In the gut, lymph nodes, spleen, and tonsil, there was some LT-beta present on a variety of lymphoid cell types. In contrast, strong staining for LT-beta was observed on plasma cells and a subpopulation of CD4+ T cells in tissues affected by chronic inflammatory disease or infection, for example in inflammatory bowel disease, and in lymph nodes obtained from patients with sarcoidosis and tuberculosis. In tuberculous and sarcoid lymph nodes, LT-beta expression also occurred on some but not all epithelioid histiocytes within granulomas and on multi-nucleated giant cells. These findings support a role for LT-beta in human disease and suggest that it might represent a therapeutic target in a variety of common infective or inflammatory disorders.     

Effects of tumor necrosis factor and lymphotoxin on peripheral lymphoid tissue development

Previously, we have reported that neutralization of surface lymphotoxin (LT-alphabeta) in mice which expressed an LT-beta receptor-Fc fusion protein, driven by the cytomegalovirus promoter, resulted in an array of anatomic abnormalities. We now report that mice which express a tumor necrosis factor (TNF) receptor p60-Fc fusion protein (which neutralizes TNF and soluble LT-alpha3 activity) develop unique lymphoid abnormalities. Our data demonstrate that some aspects of peripheral lymphoid organ development require both surface LT-alphabeta and TNF interacting with their specific receptors. However, these related cytokines are also capable of signaling distinct developmental events. Splenic MAdCAM-1 expression, follicular dendritic cell localization and normal Peyer's patch development all require both surface LT-alphabeta and TNF activity. Marginal zone formation and splenic B cell localization primarily require surface LT-alphabeta-LT-beta receptor interactions. Primary follicle formation was dependent upon TNF receptor(s) engagement. Interestingly spleen, lymph nodes and Peyer's patches from TNF receptor p60-Fc-expressing mice all develop different abnormalities, suggesting distinct pathways of development in these lymphoid organs. Thymus development appears to be independent of these signaling pathways. These results demonstrate that TNF and LT are crucial for normal peripheral, but not central lymphoid organ development.      

Identification and expression analysis of lymphotoxin-beta like homologues in rainbow trout Oncorhynchus mykiss

A lymphotoxin-beta (LT-beta) gene has been cloned and sequenced in rainbow trout and provides the first conclusive evidence for the existence of LT-beta in teleost. Two isoforms of LT-beta were isolated. LT-beta1 cDNA was composed of 952 bp (with a 139 bp 5'-UTR and a 201 bp 3'-UTR) and LT-beta2 cDNA was 836 bp (with a 237 bp 5'-UTR and a 197 bp 3'-UTR) both of which translated into a protein of 203 amino acid residues. Both isoforms contained a predicted transmembrane domain of 21 amino acid residues (Leu11-Val31) and the TNF family signature (Val104-Phe120). Homology and phylogenetic analysis of trout LT-beta's with other known TNF family member showed good similarity to TNF-N (teleost) and other LT-beta (mammals and frog). LT-beta1 and TNF-alpha (1 and 2) genes were highly expressed in unstimulated trout head kidney, spleen, gill and intestine, whereas LT-beta2 was weakly expressed only in the gill. The expression of LT-beta1 and -beta2 genes was not found in macrophage (RTS-11) and fibroblast (RTG-2) like cell lines, although the TNF-alpha2 gene was expressed in both cell lines with the TNF-alpha1 gene only expressed in RTS-11 cells. In head kidney cells, expression of LT-beta1 and TNF-alpha (1, 2) genes was increased by stimulation with PHA or LPS. The discovery of trout LT-beta will allow a more complete analysis of fish inflammatory responses.     

Contribution of transmembrane tumor necrosis factor to host defense against Mycobacterium bovis bacillus Calmette-guerin and Mycobacterium tuberculosis infections

To study the specific role of transmembrane tumor necrosis factor (TmTNF) in host defense mechanisms against bacillus Calmette-Guerin (BCG) and Mycobacterium tuberculosis infections, we compared the immune responses of TNF/lymphotoxin (LT)-alpha(-/-) mice expressing a noncleavable transgenic TmTNF (TmTNF tg) to those of TNF/LT-alpha(-/-) and wild-type mice. Susceptibility of TNF/LT-alpha(-/-) mice to BCG infection was associated with impaired induction of systemic RANTES but not of monocyte chemoattractant protein 1 (MCP-1), the development of excessive local and systemic Th1-type immune responses, and a substantially reduced inducible nitric oxide synthase (iNOS) activity. Resistance of TmTNF tg mice to BCG infection was associated with efficient activation of iNOS in granulomas and with the regulated release of local and systemic chemokines and Th1-type cytokines. However, M. tuberculosis infection of TmTNF tg mice resulted in longer survival and enhanced resistance compared to TNF/LT-alpha(-/-) mice but higher sensitivity than wild-type mice. TmTNF tg mice exhibited reduced pulmonary iNOS expression and showed an exacerbated cellular infiltration in the lungs despite a modest bacillary content. Our data thus indicate a role for TmTNF in host defense against mycobacteria by contributing to induction and regulation of Th1-type cytokine and chemokine expression leading to development of bactericidal granulomas expressing iNOS, which critically determines susceptibility versus resistance of the host to mycobacterial infections.     

Reduced antilisterial activity of TNF-deficient bone marrow-derived macrophages is due to impaired superoxide production.

Mice deficient for TNF ligand and receptor type 1 have demonstrated the importance of TNF in the host defense against Listeria monocytogenes. To investigate the particular deficiency of macrophages derived from TNF/lymphotoxin (LT)-alpha(-/-) mice in antilisterial growth control, bone marrow-derived macrophages (BMDM) were used for in vitro infection experiments. After the combined treatment with IFN-gamma and lipopolysaccharide (LPS), production of NO by wild-type (wt) and TNF/LT-alpha(-/-) BMDM was induced to comparable levels, but only wt BMDM controlled L. monocytogenes growth efficiently. Nevertheless, inhibition of NO production led to a remarkable loss of antilisterial activity. This suggests that presence of NO is necessary but not sufficient for L. monocytogenes killing and that elimination of L. monocytogenes requires additional effector molecules. The LPS-inducible superoxide production of TNF/LT-alpha(-/-) BMDM was impaired. Accordingly both scavenging of superoxide and peroxynitrite led to reduced L. monocytogenes killing by wt BMDM. In addition, peroxynitrite was able to kill L. monocytogenes in vitro. Together these findings suggest that the defective host defense of TNF/LT-alpha-deficient mice against L. monocytogenes partially stems from reduced superoxide production of macrophages due to the absence of TNF and imply a function for peroxynitrite, the reaction product of NO and superoxide, in the intracellular killing of L. monocytogenes.     

Control of experimental Trypanosoma brucei infections occurs independently of lymphotoxin-alpha induction

Trypanosome infections are marked by severe pathological features, including anemia, splenomegaly, and suppression of T-cell proliferation. We have used lymphotoxin-alpha-deficient (LT-alpha(-/-)) mice, as well as LT-alpha-tumor necrosis factor-double-deficient (LT-alpha(-/-) TNF(-/-)) mice, to analyze the contributions of these related cytokines in both induction of trypanosomosis-associated immunopathology and infection control. Moreover, as the cytokine-deficient mice used have no detectable lymph nodes and lack germinal-center formation upon immune stimulation, we have analyzed the functional importance of both the lymph nodes and spleen during experimental Trypanosoma brucei infections. First, we show that the absence of LT-alpha does not significantly alter early trypanosomosis development or pathology but does result in better control of late-stage parasitemia levels and slightly prolonged survival. This increased survival of infected LT-alpha(-/-) mice coincides with the appearance of increased chronic-stage anti-trypanosome immunoglobulin M (IgM)-IgG2a serum titers that are generated in the absence of functional peripheral lymphoid tissue and do not require germinal-center formation. Second, we show that splenectomized mice control their parasitemia to the same extent as fully immune-competent littermates. Finally, using LT-alpha(-/-) TNF(-/-) double-deficient mice, we show that in these mice T. brucei infections are very well controlled during the chronic infection stage and that infection-induced pathology is minimized. Together, these findings indicate that while increased IgM-IgG2a anti-trypanosome antibody titers (generated in the absence of LT-alpha, peripheral lymph nodes, and germinal-center formation) coincide with improved parasitemia control, it is TNF that has a major impact on trypanosomosis-associated immunopathology.     

肺癌候选抑瘤基因HLCDG1片段的验证及全长序列的克隆

目的： 对肺癌候选抑瘤基因HLCDG1片段（已知序列）进行验证,并克隆其全长cDNA序列。方法: 采用RT-PCR和末端快速扩增技术(RACE),对正常人肺组织中HLCDG1基因片段进行验证和克隆其全长cDNA序列,登录基因数据库进行比对分析。结果: 从正常人肺组织中钓取到HLCDG1基因未知的3’端和5’端序列分别为1 304 bp和1 548 bp。HLCDG1基因与人酪蛋白激酶Ⅰα（CSNK1A1）基因2号转录变体相似性达99%,score=5 544,E=0。结论: HLCDG1基因为已知的CSNK1A1基因的2号转录变体,可能参与肺癌发生发展。     

Expression of lymphotoxin-alpha by keratinocytes: a further mediator for the lichenoid reaction.

OBJECTIVE: Lichen planus (LP) represents a disease in which autoimmune mechanisms mediated by Th1 T cells are involved. Lymphotoxin-alpha (LT-alpha) represents a Th1 cytokine with proinflammatory activities in LP, as has recently been demonstrated for interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha). METHODS: Expression of LT-alpha mRNA was investigated by RT-PCR and nonradioactive in situ hybridization. Double staining methods were applied to characterize the phenotype of cells expressing LT-alpha. Cell stimulation experiments were performed on the transformed squamous cell line HaCaT. RESULTS: In contrast to normal skin, LT-alpha-specific RT-PCR products were found in all cases of LP. Cells in the inflammatory infiltrate expressing LT-alpha were identified as mainly T cells and mast cells, as shown by in situ hybridization. Furthermore, predominant LT-alpha mRNA expression could be observed in lesional keratinocytes adjacent to the band-like inflammatory infiltrate. In cell stimulation experiments, it could be shown that IFN-gamma induces LT-alpha and TNF-alpha mRNA in the human squamous cell line HaCaT, concomitant with upregulation of MHC class II and intercellular adhesion molecule-1, which could also be observed on lesional keratinocytes in LP. CONCLUSIONS: In LP, LT-alpha mRNA is predominantly expressed by lesional keratinocytes and to a lesser extent by inflammatory cells. Induction of LT-alpha in keratinocytes is closely related to the expression of TNF-alpha and MHC class II. The loci of TNF-alpha and LT-alpha map to MHC class III on chromosome 6, which is closely linked to the MHC class II gene locus. Our results suggest that stimulation of keratinocytes with IFN-gamma results in the upregulation of proinflammatory cytokines such as LT-alpha and TNF-alpha as well as MHC class II, which map to the same gene region of immunoregulatory genes on chromosome 6 and may be involved in the induction and maintenance of the disease.     

Dissecting the role of lymphotoxin in lymphoid organs by conditional targeting

Summary: Mice with inactivation of lymphotoxin β receptor (LTβR) system have profound defects in the development and maintenance of peripheral lymphoid organs. As surface LT is expressed by lymphocytes, natural killer cells, and lymphoid tissue‐initiating cells as well as by some other cell types, we dissected cell type‐specific LT contribution into the complex LT‐deficient phenotype by conditional gene targeting. B‐LTβ knockout (KO) mice displayed an intermediate phenotype in spleen as compared with mice with complete LTβ deficiency. In contrast, T‐LTβ KO mice displayed normal structure of the spleen. However, inactivation of LTβ in both T and B cells resulted in additional defects in the structure of the marginal zone and in the development of follicular dendritic cells in spleen. Structure of lymph nodes (LN) and Peyer's patches (PP) was normal in both B‐LTβ KO and T‐ and B‐LTβ KO mice, except that PPs were of reduced size. When compared across the panel of lymphocyte‐specific LT KOs, the defects in antibody responses to T‐cell‐dependent antigens correlated with the severity of defects in spleen structure. Expression of CCL21 and CCL19 chemokines was not affected in spleen, LN and PP of B‐LTβ KO and T‐ and B‐LTβ KO mice, while CXCL13 was slightly reduced only in spleen. Collectively, our data suggest the following: (i) requirements for LT signaling to support architecture of spleen, LN and PP are different; (ii) LT complex expressed by B cells plays a major role in the maintenance of spleen structure, while surface LT expressed by T cells provides a complementary but distinct signal; and (iii) in a non‐transgenic model, expression of lymphoid tissue chemokines is only minimally dependent on the expression of surface LT complex on B and T lymphocytes.