The engagement of oral‐associated lymphoid tissues during oral versus gastric antigen administration

The role of oral‐associated lymphoid tissues during induction of oral tolerance still remains elusive. Therefore, the aim was to compare T‐cell activation and induction of tolerance to ovalbumin (OVA) presented through either of two routes; deposited into the oral cavity, or the stomach, thereby bypassing the oral cavity. OVA was administered by the oral or gastric route to BALB/c mice that had received OVA‐specific DO11.10+ CD4⁺ T cells, stained with CellTrace^? Violet dye, through intravenous injection. Proliferating OVA‐specific T cells were detected in the nose‐associated lymphoid tissues (NALT) and the cervical, mesenteric and peripheral lymph nodes at different time‐points following OVA exposure. OVA‐specific T‐cell proliferation was initially observed in the NALT 1 hr after oral, but not gastric, administration. However, at day 1, proliferation at this site was also detected after gastric administration and profound proliferation was observed at all sites by day 4. For the oral route the degree of proliferation observed was lower in the peripheral lymph nodes by day 4 compared with the other sites. These results demonstrate a similar activation pattern achieved by the two routes. However, the NALT distinguishes itself as a site of rapid T‐cell activation towards fed antigens irrespective of feeding regimen. To evaluate induction of tolerance a semi‐effective OVA dose was used, to detect differences in the degree of tolerance achieved. This was performed in a model of OVA‐induced airway hypersensitivity. No differences in tolerance induction were observed between the two administration routes.     

Cryptopatches and isolated lymphoid follicles: dynamic lymphoid tissues dispensable for the generation of intraepithelial lymphocytes

In comparison to secondary lymphoid organs, gut-associated lymphoid tissues such as isolated lymphoid follicles (ILF) and cryptopatches (CP) have been less intensively studied. To gain a better insight into processes regulating organization and function of these structures, which are believed to participate in immune responses and extrathymic T cell development, we characterized the lymphoid structures of the murine small intestine in more detail. The size and cellular composition of small intestinal lymphoid aggregations were analyzed in C57BL/6 and BALB/c wild-type and lymphotoxin (LT)-deficient mice, by flow cytometry, histology and automated multi-color immunofluorescence microscopy evaluating large coherent areas of the intestine. These evaluations demonstrate that aggregated lymphoid structures in the small intestine vary in size and cellular composition, with a majority of structures not matching the current definitions of CP or ILF. Accordingly, significant variations depending on species, age and mouse strain were observed. Furthermore, small bowel transplantation revealed a rapid exchange of B but not T cells between host and grafted tissue. Moreover, LT-deficient animals lack any intestinal lymphoid aggregations yet possess the complete panel of intraepithelial lymphocytes (IEL). In summary, our observations disclose intestinal lymphoid aggregations as dynamic structures with a great deal of inborn plasticity and demonstrate their dispensability for the generation of IEL.     

Human natural killer cell development in secondary lymphoid tissues

For nearly a decade it has been appreciated that critical steps in human natural killer (NK) cell development likely occur outside of the bone marrow and potentially necessitate distinct microenvironments within extramedullary tissues. The latter include the liver and gravid uterus as well as secondary lymphoid tissues such as tonsils and lymph nodes. For as yet unknown reasons these tissues are naturally enriched with NK cell developmental intermediates (NKDI) that span a maturation continuum starting from an oligopotent CD34⁺CD45RA⁺ hematopoietic precursor cell to a cytolytic mature NK cell. Indeed despite the detection of NKDI within the aforementioned tissues, relatively little is known about how, why, and when these tissues may be most suited to support NK cell maturation and how this process fits in with other components of the human immune system. With the discovery of other innate lymphoid subsets whose immunophenotypes overlap with those of NKDI, there is also need to revisit and potentially re-characterize the basic immunophenotypes of the stages of the human NK cell developmental pathway in vivo. In this review, we provide an overview of human NK cell development in secondary lymphoid tissues and discuss the many questions that remain to be answered in this exciting field.     

B and also T lymphocytes migrate via gut lymph to all lymphoid organs and the gut wall,but only IgA+ cells accumulate in the lamina propria of the intestinal mucosa

In pigs the lymphocytes emigrating from the intestinal wall were collected by cannulating the lymphatics, labeled in vitro using a fluorescent dye and retransfused. The injection of 6.6 ± 4.2 × 10⁸ cells resulted in a labeling index between 1.5 % in intestinal lymph, 0.2 % in the spleen and lymph nodes, ∼ 0.1 % in the intestinal lamina propria and 0.003 % in intraepithelial lymphocytes. About 25 % of the injected cells were present in the blood and 1 % was recovered in the lymph. T cells were found in similar proportions in the injected and the recovered cells in the organs (70 – 80 %). The proportion of IgA⁺ cells among the immigrated cells in the intestinal lamina propria ranged from 5 to 8 %, which in absolute numbers was up to 60 % of the injected IgA⁺ cells. T and IgM⁺ cells did not show a higher accumulation in any organ. These experiments in conventional, unrestrained animals revealed that (1) T cells immigrate into the intestinal lamina propria, (2) preferential migration of IgA⁺ cells from gut lymph to the intestinal lamina propria is obvious under in vivo conditions and (3) the immigrated IgA⁺ cells represent a very small population which is difficult to detect when analyzed in relative numbers.     

Immunohistochemical heterogeneity of macrophage subpopulations in human lymphoid tissues

The mononuclear phagocytic system is composed of cells which display a marked immunohistological heterogeneity. In the present study we have investigated the immunohistochemical and enzymatic features of macrophages and accessory cells present in human lymph nodes and spleen and, as control tissues, in thymus, liver, skin and heart. Our investigation has demonstrated that macrophages present in germinal centres display an immunophenotype different from that of macrophages populating T-dependent areas. Furthermore, cells lining lymph node sinuses and splenic sinusoids express endothelial and macrophage markers, and are able to modulate their immunophenotype according to different reactive conditions. These data suggest, on immunohistochemical grounds, that macrophages populating B- and T-dependent areas as well as sinuses of human peripheral lymphoid tissues, may modulate their immunophenotype according to environmental and antigenic influences.     

Salmonid T cells assemble in the thymus, spleen and in novel interbranchial lymphoid tissue

In modern bony fishes, or teleost fish, the general lack of leucocyte markers has greatly hampered investigations of the anatomy of the immune system and its reactions involved in inflammatory responses. We have previously reported the cloning and sequencing of the salmon CD3 complex, molecules that are specifically expressed in T cells. Here, we generate and validate sera recognizing a peptide sequence of the CD3ε chain. Flow cytometry analysis revealed high numbers of CD3ε(+) or T cells in the thymus, gill and intestine, whereas lower numbers were detected in the head kidney, spleen and peripheral blood leucocytes. Subsequent morphological analysis showed accumulations of T cells in the thymus and spleen and in the newly discovered gill-located interbranchial lymphoid tissue. In the latter, the T cells are embedded in a meshwork of epithelial cells and in the spleen, they cluster in the white pulp surrounding ellipsoids. The anatomical organization of the salmonid thymic cortex and medulla seems to be composed of three layers consisting of a sub-epithelial medulla-like zone, an intermediate cortex-like zone and finally another cortex-like basal zone. Our study in the salmonid thymus reports a previously non-described tissue organization. In the intestinal tract, abundant T cells were found embedded in the epithelium. In non-lymphoid organs, the presence of T cells was limited. The results show that the interbranchial lymphoid tissue is quantitatively a very important site of T cell aggregation, strategically located to facilitate antigen encounter. The interbranchial lymphoid tissue has no resemblance to previously described lymphoid tissues.     

Enriched environment enhances NK cell maturation through hypothalamic BDNF in male mice

Macroenvironmental factors, including a patient's physical and social environment, play a role in cancer risk and progression. Our previous preclinical studies have shown that the enriched environment (EE) confers anti-obesity and anti-cancer phenotypes that are associated with enhanced adaptive immunity and are mediated by brain-derived neurotrophic factor (BDNF). Natural killer (NK) cells have anti-cancer and anti-viral properties, and their absence or depletion is associated with inferior clinical outcomes. In this study, we investigated the effects of EE on NK cell maturation following their depletion. Mice living in EE displayed a higher proportion of NK cells in the spleen, bone marrow, and blood, compared to those living in the standard environment (SE). EE enhanced NK cell maturation in the spleen and was associated with upregulation of BDNF expression in the hypothalamus. Hypothalamic BDNF overexpression reproduced the EE effects on NK cell maturation in secondary lymphoid tissues. Conversely, hypothalamic BDNF knockdown blocked the EE modulation on NK cell maturation. Our results demonstrate that a bio-behavior intervention enhanced NK cell maturation and was mediated at least in part by hypothalamic BDNF.     

Aging affects B‐cell antigen receptor repertoire diversity in primary and secondary lymphoid tissues

The elderly immune system is characterized by reduced responses to infections and vaccines, and an increase in the incidence of autoimmune diseases and cancer. Age‐related deficits in the immune system may be caused by peripheral homeostatic pressures that limit bone marrow B‐cell production or migration to the peripheral lymphoid tissues. Studies of peripheral blood B‐cell receptor spectratypes have shown that those of the elderly are characterized by reduced diversity, which is correlated with poor health status. In the present study, we performed for the first time high‐throughput sequencing of immunoglobulin genes from archived biopsy samples of primary and secondary lymphoid tissues in old (74 ± 7 years old, range 61—89) versus young (24 ± 5 years old, range 18–45) individuals, analyzed repertoire diversities and compared these to results in peripheral blood. We found reduced repertoire diversity in peripheral blood and lymph node repertoires from old people, while in the old spleen samples the diversity was larger than in the young. There were no differences in somatic hypermutation characteristics between age groups. These results support the hypothesis that age‐related immune frailty stems from altered B‐cell homeostasis leading to narrower memory B‐cell repertoires, rather than changes in somatic hypermutation mechanisms.     

Immunohistological demonstration of lymphocyte surface antigens in postmortem lymphoid tissues

Summary The postmortem stability of cell antigens has hardly been studied. Using monoclonal antibodies (mabs) we examined the postmortem detectability of lymphocyte surface antigens in different lymphoid organs by comparing two sensitive, immunohistological staining procedures.To quantify the probable degree of autolysis of the tissues a score system was applied by taking into consideration the postmortem age as well as the core temperature of the corpses.The antigens examined generally proved to be very resistant to autolytic influences. Differences were found when comparing different mabs and with regard to the type of lymphoid tissue. The loss of immunohistological reactions was most extensive in the spleen whereas tonsils showed almost no qualitative alterations in staining patterns. Reactivity of mabs with postmortem tissues decreased in the following order: Dako CD22 and anti-Leu 4, anti-Leu 3a, anti-Leu 7, Dako T8. The mabs anti-Leu 7 and Dako-T8 frequently failed to demonstrate their respective antigens but no correlation between the loss of staining and the degree of autolytic decomposition (our score) could be detected.In general, postmortem tissues as well as tissues shock frozen after delay are suitable for qualitative immunohistology of those cells characterized by the mabs applied.The APAAP-method proved unequivocally to be the superior staining technique.     

The toxic plant proteins ricin and abrin induce apoptotic changes in mammalian lymphoid tissues and intestine

The toxins ricin and abrin are potent inhibitors of protein synthesis. Apoptosis has been shown to be induced in some cells by cycloheximide and actinomycin D whereas the process is prevented in other cells by the same agents, both inhibitors of protein synthesis. We were interested to find whether ricin and abrin caused any apoptotic changes in rapidly dividing tissues where we believed that these toxins concentrate. Rats were injected intramuscularly with toxin and killed at time intervals, tissues being removed and examined by light and electron microscopy. Apoptotic-like bodies were abundant in para-aortic lymph nodes, Peyer's patches and ideal crypts of ricin or abrin intoxicated rats. Abrin was found to cause markedly more pronounced changes in these tissues, when compared with a similar dose of ricin. Prior to this, these toxins have been reported as causing necrosis in animal tissues.     

T cell binding to B lymphoid cell lines in humans: a marker for T-B cell interaction?

Binding of human circulating T cells to established normal and malignant B cell lines results in rosette formation. The percentage of B cells, circulating T cells, and thymocytes able to bind to the B-LCL Raji were 0%, 59 +/- 4% and 61 +/- 6%, respectively. The percentage of rosettes formed between Raji cells and circulating mononuclear cells from 92 normal individuals was 27.8 +/- 5.3%, and remained stable over several months. This phenomenon seems to involve relatively mature B cells, and a T cell marker which appears early in T cell ontogeny. In the peripheral blood, most of the B-LCL binding T cells exhibit a 'helper-inducer' phenotype, as determined with the monoclonal antibodies Leu 3a and OKT4. However, a significant percentage of T cells with so-called 'cytotoxic-suppressor' markers (Leu 2a and OKT8) also bind to B-LCL. The T cells involved in this morphological interactive reaction with B cells might conceivably be specifically involved in regulating B cell functions. Enumeration of this particular subset may be useful in conditions where abnormal T-B cell interactions are suspected.     

B cells and the intestinal microbiome in time,space and place

The gut immune system is shaped by the continuous interaction with the microbiota. Here we dissect temporal, spatial and contextual layers of gut B cell responses. The microbiota impacts on the selection of the developing pool of pre-immune B cells that serves as substrate for B cell activation, expansion and differentiation. However, various aspects of the gut B cell response display unique features. In particular, occurrence of somatically mutated B cells, chronic gut germinal centers in T cell-deficient settings and polyreactive binding of gut IgA to the microbiota questioned the nature and microbiota-specificity of gut germinal centers. We propose a model to reconcile these observations incorporating recent work demonstrating microbiota-specificity of gut germinal centers. We speculate that adjuvant effects of the microbiota might modify permissiveness for B cell to enter and exit gut germinal centers. We propose that separating aspects of time, space and place facilitate the occasionally puzzling discussion of gut B cell responses to the microbiota.     

宫颈粘膜相关淋巴瘤及假性淋巴瘤临床病理和免疫组化研究

目的：探讨宫颈粘膜相关淋巴瘤（ＣＭＡＬＴ－ｏｍａ）及假性淋巴瘤（ＣＰＬ）的诊断标准、鉴别诊断及发病机理。方法：ＣＭＡＬＴ－ｏｍａ及ＣＰＬ各５例，活检或手术标本做石蜡切片及免疫组化（ＡＢＣ法）染色。结果：ＣＭＡＬＴ－ｏｍａ出现“淋巴上皮病变”及单克隆增殖，２例为Ｔ小多形细胞性，３例为Ｂ细胞性（ＣＣＬ和淋巴浆细胞型）。ＣＰＬ均有多克隆性的多种炎细胞浸润。结论：大多数ＭＡＬＴ－ｏｍａ为低度恶性并有“回归”现象。因此，手术为首选治疗方法。如果肿瘤侵犯邻近脏器或转移至淋巴结，应加用化疗或放疗。ＣＰＬ应予以有效的抗菌治疗，否则，有转变成ＭＡＬＴ－ｏｍａ的可能。自身免疫性疾病及感染，可导致机体产生获得性ＭＡＬＴ，并在持续性刺激下发展为ＣＰＬ，进而转变为ＣＭＡＬＴ－ｏｍａ。     

Secondary and ectopic lymphoid tissue responses in rheumatoid arthritis: from inflammation to autoimmunity and tissue damage/remodeling

Summary: Rheumatoid arthritis is a chronic systemic inflammatory disease primarily affecting the synovium of diarthrodial joints. Despite the currently unknown etiology, overwhelming evidence indicates that both innate and adaptive immunity play a central role in disease pathogenesis. In this review, we consider recent evidence examining the mechanisms of lymphoid tissue reactivity in rheumatoid arthritis with a focus on the dynamics controlling secondary and ectopic lymphoid tissue response. We then examine the cellular and molecular mechanisms regulating the biopathology of these processes with specific emphasis on cell trafficking, contribution to autoimmunity, and joint damage-repair. We finally provide a brief overview of the most recent studies addressing the clinical relevance of synovial lymphoid tissue analysis as a diagnostic and prognostic tool as well as its response to current biological therapies.     

Diabetogenic T cells are primed both in pancreatic and gut-associated lymph nodes in NOD mice

Activation of an islet-specific immune response is an early yet essential step in autoimmune diabetes. The immune cells and antigen(s) involved in this early step and its anatomical site remain incompletely understood. To directly evaluate the site where islet-specific and diabetogenic lymphocytes are activated, we isolated lymphocytes from spleen and from pancreas-draining, gut-associated and subcutaneous lymph nodes of diabetic NOD mice and of young NOD mice, and transferred these into NOD scid/scid recipients devoid of endogenous islet-specific immune responses themselves. Although spleen lymphocytes from diabetic NOD mice induced diabetes more rapidly than lymphocytes from any other lymphoid tissue, spleen lymphocytes from young NOD donors were not superior to other lymphocytes from the same donors. At a donor-age of 6 weeks, the most-diabetogenic lymphocytes were found in pancreas-draining lymph node whereas gut-associated lymph nodes and the spleen were sources of intermediate diabetogenic activity. Lymphocytes from peripheral lymph nodes were only weakly diabetogenic at this age, and also remained the least efficient later. Surprisingly, lymphocytes isolated even from 3-week-old NOD mice had diabetogenic potential. However, such cells were almost exclusively found in gut-associated lymph nodes. This suggests that initial priming of diabetogenic cells takes place in the gut whereas pancreas-draining lymph nodes may serve as the site of amplification of the autoimmune response.     

Ocular exposure to infectious laryngotracheitis virus alters leukocyte subsets in the head-associated lymphoid tissues and trachea of 6-week-old White Leghorn chickens

ABSTRACT

Infectious laryngotracheitis virus (ILTV), an alphaherpesvirus, causes acute respiratory disease primarily infecting the upper respiratory tract and conjunctiva. Administration of live attenuated ILTV vaccines via eye drop, drinking water, or by coarse spray elicits protective mucosal immunity in the head-associated lymphoid tissues (HALT), of which conjunctiva-associated lymphoid tissue (CALT) and the Harderian gland (HG) are important tissue components. The trachea, a non-lymphoid tissue, also receives significant influx of inflammatory cells that dictate the outcome of ILTV infection. The objective of this study was to evaluate leukocyte cellular and phenotypic changes in the CALT, HG and trachea following ocular infection with a virulent ILTV strain. At 1, 3, 5, 7 and 9 days post-infection, CALT, HG, and trachea of 6-week-old specific pathogen free (SPF) chickens ocularly-exposed to vehicle or virulent ILTV strain 63140 were dissociated, the cells enumerated and then phenotyped using flow cytometry. The CALT had the highest viral genomic load, which peaked on day 3. In ILTV-infected birds, the CALT had a decreased percentage of leukocytes. This was reflected by decreased numbers of MHCI⁺MHCII^–, MHCI⁺MHCII^low+, and CD4⁺ cells, while IgM⁺ and MHCI⁺MHCII^High+ expressing cell populations increased. In the HG, the most notable change in cells from ILTV-infected birds was a decrease in IgM expressing cells and histologically, an increase in Mott cells. In summary, an acute, ocular exposure to ILTV strain 63140 in young birds shifts subsets of lymphocyte populations in the CALT and HG with minimal impact on the trachea.     

Heterogeneity of lymphoid tissue inducer cell populations present in embryonic and adult mouse lymphoid tissues

Lymphoid tissue inducer (LTi) cells have a well established role in secondary lymphoid tissue development. Here, we report on the heterogeneity of LTi cells based on their CD4 and chemokine receptor expression. The CD4⁻ LTi-cell population has a similar phenotype to the CD4⁺ population, with similar chemokine-receptor-expressing subsets. In both embryonic and adult spleen the CD4⁻ LTi-cell population is comparable as a proportion of total splenocytes to its CD4⁺ counterpart. In contrast, different proportions of CD4⁺ and CD4⁻ LTi cells are found in different lymph nodes. Both CD4⁺ and CD4⁻ LTi cells share the anatomical location and are associated with vascular cell adhesion molecule-1-positive stromal cells in spleen and lymph nodes. The numbers of both CD4⁺ and CD4⁻ LTi cells in adult spleen are augmented in the presence of B cells. With the exception of CD4, there is a strong correlation coefficient (0·89) for gene expression between the two populations. Polymerase chain reaction analysis of individual CD4⁺ and CD4⁻ LTi cells shows that a similar proportion in embryonic and adult spleen co-expressed both CXCR5 and CCR7 or CXCR5 alone: 84·6% for adult CD4⁺ and 87·6% for adult CD4⁻; 95·3% for embryonic CD4⁺ and 91·5% for embryonic CD4⁻. Consistently fewer CCR7 single-positive cells were found in the CD4⁺ and CD4⁻ fractions in the embryo.     

眼结膜黏膜相关淋巴组织边缘带B细胞淋巴瘤临床病理分析

目的 探讨眼结膜黏膜相关淋巴组织边缘带B细胞淋巴瘤(marginal zone B cell lymphoma of mucosa-associated lymphoid tissue)(简称为MALT淋巴瘤)的临床病理特征、治疗及预后.方法 对15例眼结膜MALT淋巴瘤患者的临床病理资料进行回顾性分析及随访,复查和完善HE及免疫组化染色切片,4例进行Ig基因重排克隆性分析.结果 (1)15例患者中,男性5例,女性10例,中位年龄42岁,病史平均20个月.(2)病理形态:黏膜下大量密集淋巴样细胞弥漫浸润,并有模糊淋巴滤泡样结节.浸润细胞多为小～中等大小的淋巴样细胞及单核样B细胞.(3)免疫表型:浸润细胞CD20、CD79a、BCL-2均(+),CD3、CD5、CD10、Cyclin D1、TdT均(-).(4)Ig基因克隆性分析:4例均呈单克隆.(5)随访:随访时间2～35个月,截止随访日期,所有患者均生存,且病变无复发.结论 眼结膜MALT淋巴瘤好发于中年女性,结膜红肿突起为主要特征,镜下以小细胞样边缘带B细胞为主,具有典型MALT淋巴瘤的免疫表型和惰性临床经过,预后良好.     

T cell help to B cells: Cognate and atypical interactions in peripheral and intestinal lymphoid tissues

Enduring immunity against harmful pathogens depends on the generation of immunological memory. Serum immunoglobulins are constantly secreted by long-lived antibody-producing cells, which provide extended protection from recurrent exposures. These cells originate mainly from germinal center structures, wherein B cells introduce mutations to their immunoglobulin genes followed by affinity-based selection. Generation of high-affinity antibodies relies on physical contacts between T and B cells, a process that facilitates the delivery of fate decision signals. T-B cellular engagements are mediated through interactions between the T cell receptor and its cognate peptide presented on B cell major histocompatibility class II molecules. Here, we describe the cellular and molecular aspects of these cognate T-B interactions, and highlight exceptional cases, especially those arising at intestinal lymphoid organs, at which T cells provide help to B cells in an atypical manner, independent of T cell specificity.