The kinetics of cell surface receptor expression in children perinatally exposed to polychlorinated biphenyls

Exposure to polychlorinated biphenyls (PCBs) during pre-natal and early life can alter normal immune system development. Blood specimens from newborns, 6-, and 16-month-old infants were collected in the Michalovce and Svidnik/Stropkov districts, areas with, respectively, high and low environmental PCB contamination, and lymphocyte receptor expression was evaluated by multi-color flow cytometry. The results indicate that the percentage of lymphoid dendritic cells (DC) and na?ve/resting T-lymphocytes were significantly increased at 6-months in Michalovce as compared to the same cell types in cord blood samples (p < 0.001), whereas natural regulatory T-lymphocytes and suppressor inducer T-lymphocytes were reduced (p < 0.001). Overall, a positive linear correlation of terminally differentiated effector memory (TEM) T-lymphocyte population with age, but a negative linear correlation for myeloid DC from birth to 6-months in both regions were found. Michalovce samples indicated significantly higher expression of memory T-lymphocytes (birth, 6(th), and 16(th) month), TEM T-lymphocytes (birth and 6(th) month), and lymphoid DC (6(th) month) compared to the Svidnik/Stropkov regions. After adjustment for relevant covariates, such as maternal age, parity, season of birth, breastfeeding, birth weight, and gender, the myeloid DC, suppressor inducer T-lymphocytes, truly na?ve helper/inducer T-lymphocytes, and TEM T-lymphocytes remained significantly different between districts in cord blood samples. The multivariate analysis models for 6- and 16-month samples showed district differences in all cellular determinants, except for lymphoid DC and macrophage-like cells. This study provides the first evidence that pre-natal and early post-natal exposure to PCBs affects the dynamics of cell surface receptor expression on lymphoid DC and DC-like cells, suggesting impaired immunologic development following pre-natal and early post-natal PCB exposure.     

Dynamics of lymphocyte subsets in children living in an area polluted by polychlorinated biphenyls

Immune system development, particularly in the pre-natal and early post-natal periods, has far-reaching health consequences during childhood, as well as throughout life. Exposure to poly-chlorinated biphenyls (PCBs) during pre-natal and early life has been previously associated with changes in the incidence of infectious and allergic diseases in children, and humoral immunity alterations. Lymphocyte immunophenotyping is an important tool in the diagnosis of immunologic and hematologic disorders. This study used a lysed whole blood method for analysis of lymphocyte sub-populations in samples from children born and living in two districts: a highly-contaminated area (Michalovce) and one (Svidnik/Stropkov) with ≈ 2-fold lower environmental PCB levels. The percentages of B-lymphocytes (CD19(+)), activated HLADR(+)CD19(+) cells, and CD8(+) T-lymphocytes significantly increased at 6- and 16-months-of-age in both selected regions as compared to in cord blood values (p < 0.001). Levels of CD3(+) cells increased significantly (from 61 to 65%) in samples from Michalovce (p < 0.01). Levels of CD4(+) T-lymphocytes declined 10% among 16-month-olds in both regions (Michalovce at p < 0.001 and Svidnik/Stropkov at p < 0.01). Natural killer (NK) cell levels decreased 50% in Michalovce 6- and 16-month-old children and 42% among 6-month-olds in Svidnik/Stropkov (p < 0.001). Compared with the less-contaminated region, Michalovce samples showed significantly higher expression of CD3(+) T-lymphocytes, B-lymphocytes, and activated B-lymphocytes, whereas NK cells were less expressed. Even after adjustment for selected covariates, e.g., maternal cigarette smoking, age, parity, ethnicity, birth weight, and gender of infant, the levels of CD19(+), HLADR(+)CD19(+), and CD3(-)CD(16 + 56)(+) cells were seen to remain significantly different between the districts. These results showed that early-life environmental PCB exposure was associated with fluctuations in major lymphocyte subsets in children, suggesting that there is a post-natal immune system response to PCB exposures.     

Determination of hprt mutant and mutation frequencies and the molecular characterization of human derived in vivo T-lymphocyte mutants

Using a T-lymphocyte clonal assay, 73 6-thiogua-nine resistant T-lymphocytes were isolated from two blood samples obtained 4 months apart from a 50-year-old male subject. Sixty-six of these mutants were characterized at the DNA sequence level using cDNA. One particular single base substitution was recovered a total of 23 times. The majority of T-cell receptors (TCR) of these mutants all share a common γ-TCR rearrangement, and thus likely represent a single mutational event that underwent clonal expansion in vivo. Siblings of this clone were recovered in both collections. Three other single base substitutions were also recovered more than once. In two of the three cases, the mutants were also found to be clonally related, while in one case they were not. A number of identical exon loss events were also recovered, yet none of these were clonally related. This probably reflects the multiple pathways by which these mutations can arise. The TCR data was used to correct the observed mutant frequency to produce an estimate of the actual mutation frequency. The two mutant frequencies, 18 × 10^?6 and 19 × 10^?6, obtained from the first and second sampling periods, respectively, can thus be corrected to yield true mutation frequency's of 12 × 10^?6 each © 1995 Wiley-Liss, Inc.     

HIV‐1 impairs in vitro priming of naïve T cells and gives rise to contact‐dependent suppressor T cells

Priming of T cells in lymphoid tissues of HIV‐infected individuals occurs in the presence of HIV‐1. DC in this milieu activate T cells and disseminate HIV‐1 to newly activated T cells, the outcome of which may have serious implications in the development of optimal antiviral responses. We investigated the effects of HIV‐1 on DC–naïve T‐cell interactions using an allogeneic in vitro system. Our data demonstrate a dramatic decrease in the primary expansion of naïve T cells when cultured with HIV‐1‐exposed DC. CD4⁺ and CD8⁺ T cells showed enhanced expression of PD‐1 and TRAIL, whereas CTLA‐4 expression was observed on CD4⁺ T cells. It is worth noting that T cells primed in the presence of HIV‐1 suppressed priming of other naïve T cells in a contact‐dependent manner. We identified PD‐1, CTLA‐4, and TRAIL pathways as responsible for this suppresion, as blocking these negative molecules restored T‐cell proliferation to a higher degree. In conclusion, the presence of HIV‐1 during DC priming produced cells with inhibitory effects on T‐cell activation and proliferation, i.e. suppressor T cells, a mechanism that could contribute to the enhancement of HIV‐1 pathogenesis.     

CD103+CD11b− salivary gland dendritic cells have antigen cross‐presenting capacity

Dendritic cells (DCs) in lymphoid and non‐lymphoid tissues are professional antigen‐presenting cells that are essential for effective immunity and tolerance. However, the presence and characteristics of DCs in steady‐state salivary glands (SGs) currently remain unknown. We herein identified CD64^?CD11c⁺ classical DCs (cDCs) as well as CD64⁺ macrophages among CD45⁺MHC class II⁺ antigen‐presenting cells in steady‐state murine SGs. SG cDCs were divided into CD103⁺CD11b^? and CD103^?CD11b⁺ cDCs. CD103⁺CD11b^? cDCs expressed XCR1, CLEC9A, and interferon regulatory factor 8, whereas CD103^?CD11b⁺ cDCs strongly expressed CD172a. Both cDC subsets in SGs markedly expanded in response to the Flt3 ligand (Flt3L), were replenished by bone marrow‐derived precursors, and differentiated from common DC precursors, but not monocytes. Furthermore, ovalbumin‐pulsed SG CD103⁺CD11b^? cDCs induced the proliferation of naïve ovalbumin‐specific CD8⁺ T cells and production of interferon‐γ from proliferating T cells. SG CD103⁺CD11b^? cDCs expanded by Flt3L in vivo exhibited the same properties. These results indicate that bona fide cDCs reside in steady‐state murine SGs and cDCs with the CD103⁺CD11b^? phenotype possess antigen cross‐presenting capacity. Moreover, Flt3L enhances protective immunity by expanding cDCs. Taken together, SG cDCs might play an important role in maintaining immune homeostasis in the tissues.     

Differential expression of CCL19 by DC-Lamp+ mature dendritic cells in human lymph node versus chronically inflamed skin

De novo formation of lymphoid tissue is one of the characteristic features of chronic inflammation. The formation of T cell–mature dendritic cell (DC) clusters has been previously demonstrated in chronically inflamed skin infected with Candida albicans. A functional similarity was also found between chronic inflammation and the T‐cell zone of lymph nodes (LNs), since a substantial fraction of phenotypically mature DCs in both tissues expressed CCL22 (macrophage‐derived chemokine; MDC) and were closely surrounded by memory‐type T cells expressing its receptor, CCR4. To analyse the nature of T cell–mature DC interactions further in chronically inflamed skin and LNs, the present study focuses on another chemokine system, namely CCL19 (EBI1 ligand chemokine; ELC), CCL21 (secondary lymphoid tissue chemokine; SLC) and their shared receptor, CCR7. RT‐PCR analysis revealed expression of CCL19, CCL21, and CCR7 at high levels in LNs and at low levels in inflamed skin. Using immunohistochemistry, the majority of DC‐Lamp⁺ mature DCs in the T‐cell area of LNs expressed CCL19 and were surrounded by CCR7⁺ naïve‐type lymphocytes, while CCL21 was expressed in reticular stromal cells and vascular endothelial cells. Very few mature DCs in LNs were found to express CCR7. In contrast, the majority of DC‐Lamp⁺ mature DCs in inflamed skin were totally negative for CCL19 and were surrounded by CCR7^? memory‐type T cells. Furthermore, CCL21 expression in the inflamed skin was detected in dermal lymphatic endothelial cells and rare CCR7⁺ mature DCs were mostly seen within the lymphatic vessels. In normal skin, on the other hand, no cells immunoreactive for CCL19, CCL21, or CCR7 were found. The present study thus reveals a striking difference in the function of mature DCs between LNs and chronically inflamed skin. Copyright © 2002 John Wiley & Sons, Ltd.     

Splenic stromal cells mediate IL‐7 independent adult lymphoid tissue inducer cell survival

Lymphoid tissue inducer cells (LTi) play an important role in the development of lymphoid tissue in embryos. Adult CD4⁺CD3^? LTi‐like cells present a similar phenotype and gene expression to their embryonic counterpart and have important roles in CD4⁺ T‐cell memory and lymphoid tissue recovery following viral infection. However, adult LTi‐like cells are heterogeneous populations and the factors that regulate their survival and accumulation within secondary lymphoid organs remain unclear, in particular whether the T‐zone stroma is involved. Here we report the identification and characterization of a distinct subset of podoplanin⁺ murine splenic stromal cells that support adult LTi‐like cell survival. We have identified and isolated CD45^?podoplanin⁺ stromal cell populations which have a similar but distinct phenotype to T‐zone reticular cells in LN. CD45^?podoplanin⁺ fibroblast‐like cells mediate LTi‐like cell survival in vitro; surprisingly this was not dependent upon IL‐7 as revealed through blocking Ab experiments and studies using LTi‐like cells unable to respond to γ chain cytokines. Our findings show that adult LTi‐like cells require extrinsic signals from podoplanin⁺ splenic stromal cells to survive and suggest that IL‐7 is not necessary to mediate their survival in the adult spleen.     

Dynamic changes in intrathymic ILC populations during murine neonatal development

Members of the innate lymphoid cell (ILC) family have been implicated in the development of thymic microenvironments and the recovery of this architecture after damage. However, a detailed characterization of this family in the thymus is lacking. To better understand the thymic ILC compartment, we have utilized multiple in vivo models including the fate mapping of inhibitor of DNA binding‐2 (Id2) expression and the use of Id2 reporter mice. Our data demonstrate that ILCs are more prominent immediately after birth, but were rapidly diluted as the T‐cell development program increased. As observed in the embryonic thymus, CCR6⁺NKp46^? lymphoid tissue inducer (LTi) cells were the main ILC3 population present, but numbers of these cells swiftly declined in the neonate and ILC3 were barely detectable in adult thymus. This loss of ILC3 means ILC2 are the dominant ILC population in the thymus. Thymic ILC2 were able to produce IL‐5 and IL‐13, were located within the medulla, and did not result from ILC3 plasticity. Furthermore, in WT mice, thymic ILC2 express little RANKL (receptor activator of nuclear factor kappa‐B ligand) arguing that functionally, these cells provide different signals to LTi cells in the thymus. Collectively, these data reveal a dynamic switch in the ILC populations of the thymus during neonatal development.     

High-frequency and adaptive-like dynamics of human CD1 self-reactive T cells

CD1 molecules present lipid antigens to T cells. An intriguing subset of human T cells recognize CD1‐expressing cells without deliberately added lipids. Frequency, subset distribution, clonal composition, naïve‐to‐memory dynamic transition of these CD1 self‐reactive T cells remain largely unknown. By screening libraries of T‐cell clones, generated from CD4⁺ or CD4^?CD8^? double negative (DN) T cells sorted from the same donors, and by limiting dilution analysis, we find that the frequency of CD1 self‐reactive T cells is unexpectedly high in both T‐cell subsets, in the range of 1/10–1/300 circulating T cells. These T cells predominantly recognize CD1a and CD1c and express diverse TCRs. Frequency comparisons of T‐cell clones from sorted naïve and memory compartments of umbilical cord and adult blood show that CD1 self‐reactive T cells are naïve at birth and undergo an age‐dependent increase in the memory compartment, suggesting a naïve/memory adaptive‐like population dynamics. CD1 self‐reactive clones exhibit mostly Th1 and Th0 functional activities, depending on the subset and on the CD1 isotype restriction. These findings unveil the unanticipated relevance of self‐lipid T‐cell response in humans and clarify the basic parameters of the lipid‐specific T‐cell physiology.     

Dendritic cell homeostasis is maintained by nonhematopoietic and T‐cell‐produced Flt3‐ligand in steady state and during immune responses

Lymphoid‐tissue dendritic cells (DCs) are short‐lived and need to be continuously replenished from bone marrow‐derived DC progenitor cells. Fms‐related tyrosine kinase 3 is expressed during cellular development from hematopoietic progenitors to lymphoid‐tissue DCs. Fms‐related tyrosine kinase 3 ligand (Flt3L) is an essential, nonredundant cytokine for DC progenitor to lymphoid tissue DC differentiation and maintenance. However, which cells contribute to Flt3L production and how Flt3L cytokine levels are regulated in steady state and during immune reactions remains to be determined. Here we demonstrate that besides nonhematopoietic cells, WT T cells produce Flt3L and contribute to the generation of both classical DCs (cDCs) and plasmacytoid DCs in Flt3L^?/? mice. Upon stimulation in vitro, CD4⁺ T cells produce more Flt3L than CD8⁺ T cells. Moreover, in vivo stimulation of naïve OT‐II CD4⁺ T cells with OVA leads to increase of pre‐cDCs and cDCs in draining lymph nodes of Flt3L^?/? mice in a partially Flt3L‐dependent manner. Thus, Flt3L‐mediated lymphoid tissue DC homeostasis is regulated by steady‐state T cells as well as by proliferative T cells, fostering local development of lymphoid organ resident DCs.     

New insights into the role of the aryl hydrocarbon receptor in the function of CD11c+ cells during respiratory viral infection

The aryl hydrocarbon receptor (AHR) has garnered considerable attention as a modulator of CD4⁺ cell lineage development and function. It also regulates antiviral CD8⁺ T‐cell responses, but via indirect mechanisms that have yet to be determined. Here, we show that during acute influenza virus infection, AHR activation skews dendritic‐cell (DC) subsets in the lung‐draining lymph nodes, such that there are fewer conventional CD103⁺ DCs and CD11b⁺ DCs. Sorting DC subsets reveals AHR activation reduces immunostimulatory function of CD103⁺ DCs in the mediastinal lymph nodes, and decreases their frequency in the lung. DNA‐binding domain Ahr mutants demonstrate that alterations in DC subsets require the ligand‐activated AHR to contain its inherent DNA‐binding domain. To evaluate the intrinsic role of AHR in DCs, conditional knockouts were created using Cre‐LoxP technology, which revealed that AHR in CD11c⁺ cells plays a key role in controlling the acquisition of effector CD8⁺ T cells in the infected lung. However, AHR within other leukocyte lineages contributes to diminished naïve CD8⁺ T‐cell activation in the draining lymphoid nodes. These findings indicate DCs are among the direct targets of AHR ligands in vivo, and AHR signaling modifies host responses to a common respiratory pathogen by affecting the complex interplay of multiple cell types.     

CCL21 is sufficient to mediate DC migration,maturation and function in the absence of CCL19

Mice deficient in CCR7 signals show severe defects in lymphoid tissue architecture and immune response. These defects are due to impaired attraction of CCR7⁺ DC and CCR7⁺ T cells into the T zones of secondary lymphoid organs and altered DC maturation. It is currently unclear which CCR7 ligand mediates these processes in vivo as CCL19 and CCL21 show an overlapping expression pattern and blocking experiments have given contradictory results. In this study, we addressed this question using CCL19‐deficient mice expressing various levels of CCL21. Complete deficiency of CCL19 and CCL21 but not CCL19 alone was found to be associated with abnormal frequencies and localization of DC in naïve LN. Similarly, CCL19 was not required for DC migration from the skin, full DC maturation and efficient T‐cell priming. Our findings suggest that CCL21 is the critical CCR7 ligand regulating DC homeostasis and function in vivo with CCL19 being redundant for these processes.     

Gain Properties and Distributed Feedback Laser Performance of 7F6/Poly(Styrene) Blend Films: Potential Core Material for Plastic Optical Fiber Expanding the Bandwidth to Visible Region

Optical gain properties of blue emission oligomer 7‐unit 9,9‐dihexylfluorene (7F6) and its blends with polystyrene (PS) are reported. 7F6 demonstrates high photoluminescence quantum yield (65%), low amplified spontaneous emission threshold (E_th^ASE = 0.6 kW cm^?2), high gain coefficient (g = 90.9 cm^?1), and extremely low distributed feedback laser threshold (E_th^laser = 86 W cm^?2). Unlike polymer gain materials, the phase separation between 7F6 and PS is small even in a high blending ratio. The 70 and 50 wt% 7F6/PS blends display excellent gain properties with g = 70.7 and 64.3 cm^?1, E_th^ASE = 1.1 and 2.1 kW cm^?2, and E_th^laser = 0.3 and 0.41 kW cm^?2, respectively. The photostability and thermal stability are improved significantly by blending 7F6 into PS. These results promise 7F6/PS blends as a potential core material for expanding the bandwidth of plastic optical fiber.     

Ontogeny of renin immunoreactive cells in the human kidney

Summary We studied the time of appearance of renin-immunoreactive cells in prenatal human kidneys by immunohistochemistry and transmission electron microscopy (TEM). Renin immunoreactivity was detectable as early as the 5^th or 6^th gestational week in the mesonephros and appeared at 8 weeks of gestation in the metanephros. In a 8 week old embryo renin granules were seen by TEM in the juxtaglomerular epithelioid granular cells of metanephric tissue. In the embryos delivered by prostaglandin-induced abortion, granular renin immunoreactivity was also present in the cells of the proximal convoluted tubule.Our results support the contention that the renin-angiotensin system is active during fetal life and indicates a role for renin even during the embryonic period. In addition, they document a morphologically detectable effect of prostaglandins on the distribution of renin in the kidney.Dedicated to Professor Wolfgang Zenker, Zürich, on occasion of his 60^th birthday     

Differential Adhesion Molecule Expression on Porcine Mononuclear Cell Populations

Adhesion molecule expression was analysed on porcine blood and lymphoid organ CD4⁺ CD8^? naïve T helper (Th) lymphocytes, CD4⁺ CD8⁺ memory Th lymphocytes (particular to the pig), CD4^? CD8^high cytotoxic T (Tc) lymphocytes, CD4^? CD8^low NK cells (CD3^? in the pig), CD4^? CD8^? T-cell receptor-γδ-positive (TCRγδ⁺) lymphocytes, B lymphocytes and monocytes. While CD44 expression was relatively homogeneous amongst mononuclear cells, differences were noted for the integrins. Blood naïve Th lymphocytes were CD49d^low CD11a^low, as were splenic naïve Th cells; blood memory Th lymphocytes were CD49d^high CD11a^low, splenic memory Th cells were CD49d^high CD11a^high with a CD49d^high CD11a^low subpopulation; blood Tc lymphocytes were mainly CD49d^low CD11a^low, and splenic cells were CD49d^high CD11a^high. Lymph node lymphocytes were more homogeneous in their integrin expression. These were relatively CD49d^low CD11a^low, except the memory Th lymphocytes which had higher integrin expression. B lymphocytes related to the majority of integrin^low T cells, while monocytes and NK cells were CD49d^high CD11a^high; γδ T lymphocytes showed variable CD49d expression but a CD11a^high phenotype. CD49d^high CD11a^high co-expression was found, and this phenotype was typical of, but not exclusive to, CD25⁺ (activated) lymphocytes. These results demonstrated that porcine memory Th lymphocytes and NK cells, as well as activated cells, would have increased integrin-dependent activities compared with naïve Th lymphocytes, and integrin-dependent reactions would probably vary between blood and lymphoid organ cells.     

T-Cell stimulation and regulation: With complements from CD46

Crosslinking of CD46 and CD3 on naïve human CD4⁺ T-lymphocytes induces interleukin-10 secretion and granzyme B expression. These highly proliferative T-regulatory type 1-like T-regulatory T-cells (Tregs) can suppress an immune response. We propose that this process is important in the prevention of chronic inflammation such as at epithelial borders and in deactivation of a successful immune response. Relative to the latter, once a complement-fixing polyclonal antibody response has been mounted, in most cases, the pathogen will be rapidly destroyed. At this time, the C3b/C4b-bearing immune complexes could initiate the deactivation arm of an immune response by shutting down immunocompetent cells through CD46-generated T-cells. Herein, we review this pathway for the induction of Tregs, focusing on a role for the complement system and especially signaling through CD46 on human T-cells.     

Cytomegalovirus‐seropositivity has a profound influence on the magnitude of major lymphoid subsets within healthy individuals

Cytomegalovirus (CMV) infects most individuals and elicits a strong CMV‐specific immune response. We have studied the influence of CMV‐seropositivity on the size of lymphoid subsets in healthy donors and demonstrate that the virus substantially modulates the peripheral lymphoid pool. CD8⁺ T cell numbers are increased in all CMV‐seropositive individuals because of a striking 60% increment in the CD8⁺ T cell memory pool. The CD45RA⁺ resting memory pool is doubled after CMV infection and increases further with age. The magnitude of the naïve CD8⁺ T cell pool is dramatically reduced in CMV‐seropositive individuals at all ages, and this accelerates the physiological decline by approximately 40 years. The number of CD4⁺ effector memory T cells is increased in CMV‐seropositive individuals and is differentially accommodated by a reduction in the number of naïve and central memory CD4⁺ T cells in young and elderly donors respectively. CMV‐seropositivity also increases the total number of B cells in older donors and suppresses the number of CD5⁺ B cells. These data reveal that CMV has a profound influence on the immune system of all healthy individuals and add to growing concern regarding the clinical and immunomodulatory significance of CMV infection in healthy donors.     

Impaired function of dendritic cells translocating the liver sinusoids: A veto effect contributing to intrahepatic tolerance?

Due to its unique architecture and conditions of blood flow, the liver is acknowledged as an immunologically unusual organ associated with primary activation of naïve T cells and the induction of tolerance. Several mechanisms have been proposed to be involved in this process. Most suggest that naïve T cells activated in situ in the hepatic sinusoids are deleted or silenced following activation by liver cells acting as antigen presenting cells. Hepatocytes, liver sinusoidal endothelial cells and bone marrow‐derived cells (including Kupffer cells and DC) have been shown to support primary activation in situ and play some role in tolerance induction. Although most liver DC have been described to be immature and located in sites inaccessible to naïve T cells, some blood‐borne DC have been shown to translocate via the sinusoids where naïve T cells recirculate. Thus, the presence of mature DC with potential immunogenicity in the sinusoids might give contradictory signals to the naïve T cells activated within this organ. In this issue of the European Journal of Immunology, liver sinusoidal endothelial cells are shown to impair the DC ability to induce the proliferation of naïve T cells in vitro via an unknown mechanism. Although these findings need to be confirmed in a physiological setting, regulation of the function of DC translocating the sinusoids might represent a new mechanism contributing to T cell tolerance in the liver. See accompanying article: http://dx.doi.org/10.1002/eji.200738060