Dendritic cell expansion occurs in mesenteric lymph nodes of B10.BR mice infected with the murine nematode parasite Trichuris muris

Dendritic cells (DCs) are a crucial element in the immune system and bridge innate and adaptive immunity. CD11c+ B220- DCs residing in Peyer's patches (PPs) have the ability to produce interleukin 10 (IL-10) and induce T helper (Th2) development. Evidence suggests that CD11c+ B220- DCs maintain the gut environment by suppressing Th1 responses with IL-10, resulting in a Th2-dominat gut environment. Th2 effectors are required for protection against the murine nematode parasite Trichuris muris, and thus CD11c+ B220- DCs may be involved in the induction of Th2 cells in T. muris infection. In the present study, the kinetics of CD11c+ B220- DCs were analyzed in mesenteric lymph nodes of B10.BR mice infected with the E-J isolate of T. muris, and the cellular expansion of CD11c+ B220- DCs was also observed. As well, the DC expansion was consistent with the occurrence of worm expulsion augmented by IL-4 and IL-13. The evidence here suggests the involvement of CD11c+ B220- DCs in protective Th2 responses to T. muris infection.     

B-cell activation in the mesenteric lymph nodes of resistant BALB/c mice infected with the murine nematode parasite Trichuris muris

Immune responses in resistant BALB/c mice infected with the murine nematode parasite Trichuris muris were examined. Following the establishment of infection, worm burdens of T. muris were expelled by BALB/c mice by day 21 postinfection (p.i.). Specific immunoglobulin G₁ (IgG₁) antibodies to T. muris excretory/secretory (E/S) antigens were detected in sera from infected mice, though specific IgG_2a antibodies were not observed during infection. Ig-producing cells increased in the mesenteric lymph nodes (MLN) of infected mice on days 7, 14, and 21 p.i., with the greatest increase in numbers of IgG- and IgA-producing cells occurring on day 14. Marked increases in the relative percentages of B220⁺ and surface Ig⁺ (sIg⁺) cells were observed in the MLN of infected mice on days 14 and 21 p.i. Furthermore, cellular expansion of the MLN in infected mice resulted in an increase in the absolute numbers of B220⁺ and sIg⁺ cells. The levels of interleukin 2 (IL-2), IL-4, and interferon-γ (IFN-γ) detected in the supernatants from concanavalin A-stimulated MLN cells of infected mice were higher than those found in normal mice. Consequently, the expulsion of T. muris in resistant BALB/c mice was concomitant with cytokine production and B-cell activation in the MLN of infected mice. These results suggest the involvement of B-cell responses in protective immunity to T. muris infection. Received: 12 May 1998 / Accepted: 5 August 1998     

Dendritic cells have a crucial role in the production of cytokines in mesenteric lymph nodes of B10.BR mice infected with Trichuris muris

Dendritic cells bridge innate and adaptive immunity and establish protective immunity to pathogens. Protection against the murine nematode parasite Trichuris muris depends on the T helper 2 (Th2) response and requires the Th2 cytokines interleukin 4 (IL-4), IL-10, or IL-13. To examine if the Th2 response to T. muris infection is regulated by CD11c⁺B220⁻ dendritic cells in mesenteric lymph nodes, dendritic cell-enriched and dendritic cell-depleted fractions were obtained from mesenteric lymph node cells of T. muris-infected mice, and production of cytokines in cultures of these fractions was measured. At day 14 postinfection, no worm expulsion was observed, and high levels of interferon γ production occurred in dendritic cell-enriched fractions. Expulsion of worms occurred on days 20 and 25 postinfection, and IL-10 production was induced in dendritic cell-enriched fractions on these 2 days. No cytokine production was observed in mesenteric lymph node cells and dendritic cell-depleted fractions during T. muris infection. The occurrence of worm expulsion was consistent with IL-10 production in dendritic cell-enriched fractions. IL-10 inhibits Th1 cells and promotes the Th2 response, and results from this study suggest that CD11c⁺B220⁻ dendritic cells in the mesenteric lymph nodes are required for IL-10 production and the IL-10-dependent protective Th2 response.     

IgE antibody production is associated with suppressed interferon-gamma levels in mesenteric lymph nodes of rats infected with the nematode Nippostrongylus brasiliensis.

IgE and IgG2a antibody production and interferon (IFN)-gamma secretion were studied in rats infected with the gut nematode Nippostrongylus brasiliensis by in vitro cultivation of mononuclear cells obtained from spleen (SPL), mesenteric lymph nodes (MLN) and pulmonary hilar lymph nodes (PLN). The highest levels of IgE were detected in the culture supernatants of MLN cells after infection: IgE levels were modest in PLN and negligible in SPL. In contrast, the highest levels of IgG2a were produced by PLN cells, followed by MLN and SPL cells. These results indicate that the MLN is the most significant site for IgE production in nematode infection, while IgG2a production is more marked in PLN. In naive rats, the spontaneous secretion of IFN-gamma was highest in PLN cells, followed by MLN and SPL cells. After the infection, IFN-gamma levels were significantly decreased in MLN and PLN. Suppression of IFN-gamma secretion was also observed in concanavalin A (ConA)-stimulated MLN and PLN cells from infected rats. In MLN, the ratio of CD4+ to CD8+ T cells was increased after the infection. Stimulation with an allergen-rich, excretory-secretory (ES) substance of the nematode enhanced ongoing IgE production, and suppressed IFN-gamma secretion by MLN and PLN cells. In contrast, an allergen-poor, adult worm extract potentiated IFN-gamma secretion. These results show that nematode-induced IgE antibody response is associated with the suppressed production and/or secretion of IFN-gamma, particularly in the MLN, and that some molecules in the ES substance may trigger these immune responses.     

Comparative studies on the levels of serum IgG1 and IgG2a in susceptible B10.BR mice infected with different strains of the intestinal nematode parasite Trichuris muris

Comparative studies were carried out on the levels of serum IgG1 and IgG2a in susceptible B10.BR mice infected with different strains of Trichuris muris (E-J and S strains). As infection proceeded, levels of IgG1 and IgG2a increased in mice infected with either strain until at least day 32 post-infection (p.i.). There were no differences in the IgG1 levels on days 14, 20, and 25 p.i. between mice infected with either E-J or S strain, whereas IgG2a levels on days 20, 25, and 32 p.i. were higher in S-infected mice than those in E-J-infected mice. Isotype switching to IgG2a is entirely dependent on interferon gamma (IFN-gamma) and, according to our previous results, the period of high IFN-gamma production in S-infected B10.BR mice is long compared to E-J-infected B10.BR mice. Thus, increased levels of IFN-gamma may sustain high levels of serum IgG2a in S-infected mice. Taken together, levels of serum IgG2a are useful markers of IFN-gamma production in T. muris infection.     

Mast cell responses in mesenteric lymph nodes to infection of rats with the nematode, Nippostrongylus brasiliensis

The number of mast cells and their distribution in rat mesentery lymph nodes were assessed after a primary infection and after several successive infections with the nematode, Nippostrongylus brasiliensis. Following primary infection with N. brasiliensis, two peaks in total mast cell counts were observed. An initial small increase was restricted to day 5 and to the region of entrance to the lymph node. During the second peak, a marked increase in the number of mast cells occurred after day 15, the majority of cells is migrating through the afferent lymphatics, and then advancing from the cortical to the medullary region. The number of cells found in the hilus always remained low, indicating that mast cells accumulate and degranulate within the lymphoid organ.

In rats infected several times with the nematode parasite, mast cell numbers were markedly increased and the distribution pattern was similar to that found on day 21 after a primary infection. The observation that the percentage of cells found in the capsule was rather low in these animals indicates that local proliferation might have contributed to the high mast cell counts.

     

Localization of IgG1-producing cells within a hyperstimulated lymph node of mice infected with an intestinal nematode parasite

In the coeliac lymph node of IgG₁ hypergammaglobulinaemic BALB/c mice infected with the intestinal nematode, Nematospiroides dubius, the bulk of in vitro production of biosynthetically-labelled IgG₁ appeared to be concentrated in the cortical regions of the node and not the medulla. This was demonstrated by incubating segments of the grossly enlarged lymph node with [³H]leucine and assessing [³H]IgG₁ production by a protein A-Sepharose binding method.     

Dendritic cell accumulation in draining lymph nodes during the induction phase of contact allergy in mice

Draining lymph node cells isolated from mice 24 h following topical exposure to a variety of contact-sensitizing chemicals, including the dinitrobenzene derivatives, 2,4-dinitrochlorobenzene and 2,4-dinitrothiocyanobenzene, contained increased numbers of dendritic cells (DCs). The increase in frequency of DCs was time-dependent and preceded significant changes in either lymph node cellularity or lymph node cell proliferative activity. The degree of DC accumulation was also influenced by the chemical used and the concentration employed for sensitization. In the context of contact allergy, the biological relevance of this phenomenon to the induction of hapten-specific responses is indicated by the fact that relatively small numbers of DC--enriched fractions of lymph node cells (comprising approximately 70% DCs), but not unfractionated or DC--depleted populations, transferred sensitization to naive animals. Moreover, using the skin-sensitizing fluorochrome, fluorescein isothiocyanate, it was observed that 24 h following exposure the majority of lymph node cells bearing high concentrations of antigen were within the DC-rich fraction.     

人胎中后期肠系膜淋巴结及相关T、B细胞的发育

目的从形态学的角度探讨人胎中后期肠系膜淋巴结的发育。方法采用常规组织学H-E染色和免疫组织化学法染色及图像分析进行研究,观察人胎中后期肠系膜淋巴结及相关T、B细胞的发育情况,相关数据做统计学处理。结果自第7个月龄起,在胚胎早期已形成的淋巴结周边的皮质继续增厚,可辨别浅层皮质与副皮质区,浅层皮质中的初级淋巴小结随胎龄的增加而增多,至出生时淋巴结内均未发现生发中心,仍为初级淋巴小结。早期的髓质随胎龄的增加被淋巴结周边增厚的皮质挤向淋巴结的中央。胚胎发育到第7～8个月龄时,随着淋巴结发育加速,淋巴结皮质逐渐增厚,可观察到分布在皮质内的CD3、IgM阳性细胞出现较强的阳性反应,第9～10个月龄时,CD3、IgM阳性细胞出现强阳性反应,灰度具有显著性差异P0.05。结论①出生时肠系膜淋巴结形态结构基本成熟,淋巴小结仍为初级淋巴小结。②人胎肠系膜淋巴结具有潜在的CD3、IgM合成和释放能力,对腹腔内免疫乃至整个免疫系统有重要作用。     

Early induction of gamma interferon and interleukin-10 production in draining lymph nodes from mice infected with Borrelia burgdorferi

Lymph node (LN) cells from C3H/HeJ mice (Lyme disease susceptible) infected for 1 week with Borrelia burgdorferi strain JD1 produced higher levels of gamma interferon (IFN-gamma) when stimulated in vitro with B. burgdorferi spirochetes than equivalent cells from B. burgdorferi-infected C57BL/6J mice (disease resistant). The interleukin-10 (IL-10) levels were comparable in the two strains, whereas the IL-4 levels were below detection limits. B. burgdorferi-stimulated LN cells from C57BL/6J mice produced significantly higher levels of IFN-gamma in the presence of neutralizing anti-IL-10 antibody than cells cultured with B. burgdorferi alone. No effect of IL-10 neutralization on IFN-gamma production by LN cells from C3H/HeJ mice was observed. Neutralizing antibody to IFN-gamma had no effect on the production of IL-10 by LN cells from C57BL/6J mice. A slight decrease in IL-10 production was detected in culture supernatants of equivalent cells from C3H/HeJ mice. The differential effect of IL-10 on IFN-gamma production in C57BL/6J and C3H/HeJ mice suggests that IL-10 is probably involved in the regulation of IFN-gamma production by LN cells during infection and may be at the root of the differential susceptibility to Lyme arthritis in these two strains of mice.     

Lactic dehydrogenase virus infection enhances parasite egg production and inhibits eosinophil and mast cell responses in mice infected with the nematode Nippostrongylus brasiliensis.

The effects of lactic dehydrogenase virus (LDV) infection on the protective immune responses to the nematode Nippostrongylus brasiliensis were studied. Mice with chronic LDV infection showed significantly higher levels of parasite egg production than non-LDV-infected (control) mice after N. brasiliensis infection. Concurrent LDV infection also suppressed peripheral blood eosinophilia and the lung mastocytosis induced by this nematode. LDV infection showed higher expression levels of the interferon-gamma (IFN-gamma) mRNA in lymph nodes compared with control mice before N. brasiliensis infection. In addition, the IgG2a production in LDV-infected mice was higher than that in control mice before and after N. brasiliensis infection. These results suggest that LDV infection modulates protective immune responses against N. brasiliensis infection by the activation of T-helper type 1 cells.     

Formation of lymph follicles and germinal centers in the somatic and mesenteric lymph nodes of growing mice during ontogenesis

We investigated the age-dependent changes that occur in the numbers of lymph follicles and germinal centers in various lymph nodes in BALB/C and ICR mice aged between four days and 16 to 18 weeks. Young adult BALB/C mice have a relatively small body size, compared to ICR mice at the same stage, where there is a relatively large body size. In BALB/C mice somatic (popliteal, brachial, axillary, inguinal, submandibular and deep cervical) and mesenteric lymph nodes were examined. In ICR mice only the somatic (popliteal, brachial and axillary) lymph nodes were examined. In both BALB/C and ICR mice, the primary follicles were apparent in most somatic nodes by the 6th postnatal day. Up to 28 days of age, the number of follicles per node increased, reaching different levels in nodes from different locations. Thereafter, in most of the somatic nodes in BALB/C mice the number of follicles increased only slightly, although there was a substantial increase in ICR mice, reaching a peak or a plateau at 8 or 12 weeks of age. In the mesenteric (ileocecal) nodes in BALB/C mice, the primary follicles first appeared at 10 to 12 days, then there was a linear increase until a plateau level was reached at 8 weeks of age. Germinal centers appeared in the mesenteric nodes at 28 days and increased rapidly in number thereafter. In most somatic nodes germinal centers were scarcely observable until 8 weeks of age. Based on our observations we have three suggestions. Firstly, in BALB/C mice there were two different patterns of age-dependent changes in the numbers of lymph follicles in the somatic and the mesenteric nodes during ontogenesis. These different patterns are probably due to variations in the magnitude of the exogenous antigen stimulatory effect. Secondly, it seems likely that the variations in the numbers of lymph follicles that are produced in somatic nodes at different locations during the first 28 days after birth relate to the dimensions of the body regions that are drained by that particular somatic node at that stage of development. Thirdly, in the relatively small BALB/C mice, the ontogenetic production of lymph follicles in a somatic node is mostly completed during the first four weeks of life, whereas in the relatively larger ICR mice, this process may continue until the young adult stage of 8 weeks.     

Amastigote load and cell surface phenotype of infected cells from lesions and lymph nodes of susceptible and resistant mice infected with Leishmania major

Cells of the dendritic cell (DC) lineage, by their unique ability to stimulate naive T cells, may be of crucial importance in the development of protective immune responses to Leishmania parasites. The aim of this study was to compare the impact of L. major infection on DCs in BALB/c (susceptible, developing Th2 responses), C57BL/6 (resistant, developing Th1 responses), and tumor necrosis factor (TNF)(-/-) C57BL/6 mice (susceptible, developing delayed and reduced Th1 responses). We analyzed by immunohistochemistry the phenotype of infected cells in vivo. Granulocytes (GR1(+)) and macrophages (CD11b(+)) appear as the mainly infected cells in primary lesions. In contrast, cells expressing CD11c, a DC specific marker, are the most frequently infected cells in draining lymph nodes of all mice tested. These infected CD11c(+) cells harbored a particular morphology and cell surface phenotype in infected C57BL/6 and BALB/c mice. CD11c(+) infected cells from C57BL/6 and TNF(-/-) C57BL/6 mice displayed a weak parasitic load and a dendritic morphology and frequently expressed CD11b or F4/80 myeloid differentiation markers. In contrast, some CD11c(+) infected cells from BALB/c mice were multinucleated giant cells. Giant cells presented a dramatic accumulation of parasites and differentiation markers were not detectable at their surface. In all mice, lymph node CD11c(+) infected cells expressed a low major histocompatibility complex II level and no detectable CD86 expression. Our results suggest that infected CD11c(+) DC-like cells might constitute a reservoir of parasites in lymph nodes.     

Enhanced hematopoietic activity accompanies parasite expansion in the spleen and bone marrow of mice infected with Leishmania donovani

In this study, we have analyzed hematopoietic activity in the spleen, bone marrow, and blood of BALB/c and scid mice infected with Leishmania donovani. Our analysis demonstrates that infection induces a rapid but transient mobilization of progenitor cells into the circulation, associated with elevated levels of granulocyte/macrophage colony-stimulating factor (GM-CSF) and MIP-1alpha. From 14 to 28 days postinfection, when parasite expansion begins in the spleen and bone marrow, both the frequency and cell cycle activity of hematopoietic progenitors, particulary CFU-granulocyte, monocyte, are dramatically increased in these organs. This is associated with increased accumulation of mRNA for GM-CSF, M-CSF, and G-CSF, but not interleukin-3. Our data also illustrate that hematopoietic activity, as assessed by changes in the frequency of progenitor cell populations and their levels of cell cycle activity, can be regulated in both a T-cell-independent and T-cell-dependent, as well as in an organ-specific, manner. Collectively, these data add to our knowledge of the long-term changes which occur in organs in which L. donovani is able to persist.     

日本血吸虫感染小鼠肠系膜淋巴结T细胞亚群的变化

目的:观察C57BL/6小鼠感染日本血吸虫(Schistosome japonicum,Sj)4～6周肠系膜淋巴结T细胞亚群的改变。方法:用Sj尾蚴腹贴法建立Sj感染的小鼠模型。4～6周后取肠系膜淋巴结做淋巴细胞计数,使用细胞内细胞因子染色的方法,利用流式细胞仪检测肠系膜淋巴结淋巴细胞中分泌不同细胞因子的T细胞亚群含量的变化。结果:Sj感染C57BL/6小鼠4～6周后,肠系膜淋巴结细胞数量明显增多;流式细胞仪检测发现肠系膜淋巴结中CD4+T细胞中分泌IFN-γ的Th1细胞增多1倍,分泌IL-4和IL-5的Th2细胞增多近20倍,Th1/Th2轴发生偏移;分泌IL-17的Th17细胞也增多近5倍;分泌IFN-γ的CD8+T细胞也增多1倍。结论:日本血吸虫感染C57BL/6小鼠4～6周肠系膜淋巴结细胞增多,并向Th2和Th17型细胞极化。     

人胎肠系膜淋巴结组织发生及相关T、B细胞的发育

目的:从形态学的角度探讨人胎肠系膜淋巴结组织发生及相关T、B细胞的发育.方法:收集人胎33例,测量顶臀长,按Patten法确定胎龄.采用常规组织学H-E染色,免疫组织化学法,观察人胎肠系膜淋巴结组织发生及相关T、B细胞的发育.结果:9周,人胎肠系膜淋巴结原基形成,IgM阳性细胞出现,散在分布;11周,出现CD3阳性细胞,原基中有高内皮微静脉;15周,形成早期髓质;23周,IgM阳性细胞集聚形成小结状.连续切片显示,CD3阳性细胞分布在小结深面形成薄层副皮质区,可辨认皮质和髓质;至28周时,淋巴小结内均未发现生发中心.结论:9周淋巴结原基出现.15周早期髓质形成,髓质形成早于皮质.23周皮、髓质明显可辨,皮质内出现淋巴小结,但至28周时小结仍为初级淋巴小结;9周出现B细胞;11周出现T细胞.