Magnetic biomonitoring of atmospheric dust using tree leaves of Ficus benjamina in Querétaro (México)

There are limited economic and reliable tools to monitor the effects of airborne particulate matter PM originating from rapid industrialization, urbanization, population growth, and economic development. It is now well established that urban PM contains magnetic particles along with other air pollutants. The velocity and temporal variability of the deposition of such PM on tree leaves are subject to the pollution sources, climate, and local atmospheric conditions. Therefore, these variables have to be taken into account during a biomonitoring. This study presents a magnetic biomonitoring in the city of Querétaro. In the city's metropolitan area, the most abundant and perennial tree species for biomonitoring is Ficus benjamina. For leaves of this species, the number of days needed for collection NDNC was measured, taking into account the meteorological conditions and the time at which they reached the saturation of airborne PM (pollutants). By means of sequential sampling, we identified that the minimum NDNC after a rainfall > 3 mm is 15 days. In such a period, total suspended particle TSP depositions reach its dynamic equilibrium. This behavior can be observed from measurements of specific magnetic susceptibility χ in Ficus benjamina samples and their comparison with TSP depositions collected with traditional Hi-Vol monitoring systems. After the NDNC calculation, a magnetic monitoring was performed with the biomonitor Ficus benjamina to evaluate the air quality at different sites in the metropolitan area every month for a period of 5 months. Values of χ ranged from 0.45 to 18.52 × 10^-8m³kg^-1. The species Ficus benjamina can be used as a biomonitor in the city of Querétaro only in seasons (winter-spring) with no or low rainfall. The species has the advantage of providing current PM information about a specific period of time.

Discovery of the fossil otter Enhydritherium terraenovae (Carnivora, Mammalia) in Mexico reconciles a palaeozoogeographic mystery

The North American fossil otter Enhydritherium terraenovae is thought to be partially convergent in ecological niche with the living sea otter Enhydra lutris, both having low-crowned crushing teeth and a close association with marine environments. Fossil records of Enhydritherium are found in mostly marginal marine deposits in California and Florida; despite presence of very rich records of fossil terrestrial mammals in contemporaneous localities inland, no Enhydritherium fossils are hitherto known in interior North America. Here we report the first occurrence of Enhydritherium outside of Florida and California, in a land-locked terrestrial mammal fauna of the upper Miocene deposits of Juchipila Basin, Zacatecas State, Mexico. This new occurrence of Enhydritherium is at least 200 km from the modern Pacific coastline, and nearly 600 km from the Gulf of Mexico. Besides providing further evidence that Enhydritherium was not dependent on coastal marine environments as originally interpreted, this discovery leads us to propose a new east-to-west dispersal route between the Florida and California Enhydritherium populations through central Mexico. The proximity of the fossil locality to nearby populations of modern neotropical otters Lontra longicaudis suggests that trans-Mexican freshwater corridors for vertebrate species in riparian habitats may have persisted for a prolonged period of time, pre-dating the Great American Biotic Interchange.

Toward gene therapy for human CD3 deficiencies

The CD3 subunits of the T cell receptor-CD3 complex (TCR-CD3) help to regulate surface TCR-CD3 expression, and participate in signal transduction leading to intrathymic selection and peripheral antigen recognition by T lymphocytes. Humans who lack individual CD3 chains show impairments in the expression and activation-induced downregulation of TCR-CD3, and the defective immune responses that result may be lethal. We have investigated delivery of a normal CD3 chain to treat disorders of this type. Retroviral transduction of CD3gamma into CD3gamma-deficient peripheral blood T lymphocytes from two unrelated patients selectively corrected the observed TCR-CD3 expression and downregulation defects, but unexpectedly seemed to cause adverse effects that can be explained by an autoreactive recognition mechanism. These data support the feasibility of gene therapy for human CD3 deficiencies, but also suggest that gene transfer into postthymic lymphocytes carrying mutations on T cell recognition or activation pathways may disrupt their intrathymic calibration and become harmful to the host.

Characterization of Herpesvirus saimiri-transformed T lymphocytes from common variable immunodeficiency patients

Common variable immunodeficiency (CVID) is a very frequent but heterogeneous syndrome of antibody formation. The primary defect remains unknown, but many reports describe peripheral blood T lymphocyte dysfunctions in a substantial proportion of CVID patients, which may impair T--B cell collaboration. In order to investigate whether such putative defects were intrinsic to T cells or, rather, secondary to quantitative differences in T cell subset distribution, or to other described disorders, we have used Herpesvirus saimiri (HVS) for the targeted transformation of CVID CD4+ and CD8+ T cells and subsequent functional evaluation by flow cytometry of their capacity to generate cell surface (CD154, CD69) or soluble (IL-2, TNF-alpha, IFN-gamma) help after CD3 engagement. Unexpectedly, the results showed that 40 different CVID blood samples exposed to HVS gave rise with a significantly increased frequency to transformed CD4+ T cell lines, compared to 40 age-matched controls (27% versus 3%, P < or = 0.00002) suggesting the existence of a CVID-specific signalling difference which affects CD4+ cell transformation efficiency. The functional analysis of 10 CD4+ and 15 CD8+ pure transformed T cell lines from CVID patients did not reveal any statistically significant difference as compared to controls. However, half of the CD4+ transformed cell lines showed CD154 (but not CD69) induction (mean value of 46.8%) under the lower limit of the normal controls (mean value of 82.4%, P < or = 0.0001). Exactly the same five cell lines showed, in addition, a significantly low induction of IL-2 (P < or = 0.04), but not of TNF-alpha or IFN-gamma. None of these differences were observed in the remaining CD4+ cell lines or in any of the transformed CD8+ cell lines. We conclude that certain CVID patients show selective and intrinsic impairments for the generation of cell surface and soluble help by CD4+ T cells, which may be relevant for B lymphocyte function. The transformed T cell lines will be useful to establish the biochemical mechanisms responsible for the described impairments.

Cell surface phenotype and cytokine secretion in Caco-2 cell cultures: increased RANTES production and IL-2 transcription upon stimulation with IL-1beta

Caco-2 is a colonic tumour cell line which, when cultured, spontaneously exhibits enterocyte-like characteristics. Given the difficulties in maintaining long-lasting cultures of enterocytes, this cell line may be a suitable in vitro model to carry out experiments trying to delineate the involvement of enterocytes in local immune responses, and their role in pathology. It seems then reasonable to obtain a detailed immune analysis of Caco-2, and compare it with available data on enterocytes. Cytofluorometry revealed several leukocyte markers on Caco-2, present also on human enterocytes. These markers include surface proteases (CD10, CD13 and CD26), antigen-presenting cell markers (CD13, CD14, CD35 and CD63), integrins (CD18 and CD61), epithelial/endothelial markers (CD21, CD31, CD47 and CD59) and finally, CD25 and CD28. In contrast to enterocytes, HLA-class 11 molecules are not found on Caco-2, whether resting or gamma-IFN-stimulated. Moreover, culture experiments with allogeneic lymphocytes revealed that Caco-2 cells were unable to induce their proliferation. Cytokine analysis showed an increased RANTES synthesis and IL-2 transcription upon stimulation with IL-1beta. Finally, amongst RANTES receptors, CCR1 is found on Caco-2 cells, whereas CCR3 and CCR5 are not.

Membrane and transmembrane signaling in Herpesvirus saimiri-transformed human CD4(+) and CD8(+) T lymphocytes is ATM-independent

In the genetic disorder ataxia telangiectasia (AT), humoral (B) and cellular (T) immunological abnormalities are frequently observed. As a consequence, AT patients are predisposed to life-threatening sinopulmonary infections. The pathogenic mechanisms remain unknown, but a role for ATM in signal transduction from membrane receptors has been proposed. We have explored the effects of a defective ATMgene on isolated human T-lineage cells from 13 AT patients with proven T cell dysfunction by transforming their CD4(+) and CD8(+) T lymphocytes with Herpesvirus saimiri, and analyzing their signaling behavior as compared to normal controls. Several functional parameters were assayed in response to both membrane (anti-CD3 and IL-2) and transmembrane (phorbol myristate acetate plus the calcium ionophore ionomycin) stimuli: (i) calcium mobilization, (ii) induction of activation molecules (CD25, CD40 ligand, CD69 and CD71), (iii) cytokine synthesis (IL-2 and tumor necrosis factor-alpha) and (iv) proliferation. All these early and late activation events were found to be normal in the transformed ATM-/-T cells, indicating that ATM is not necessary for their induction. As expected, ATM-/- transformed T cells showed an increased radiosensitivity by both radioresistant DNA synthesis and cell survival assays. In contrast to an earlier report testing transformed B lymphocytes, our results indicate that transformed mature peripheral T lymphocytes from AT patients do not have intrinsic immune function defects. Rather, the described T-lineage signaling impairments observed in patients may be secondary in vivo to extrinsic ATM-dependent suppressive factors and/or to a developmental defect. These transformed T cells may help to understand the distinct biological role of ATM in different cell types and to develop rational therapies for the immunological dysfunction of AT patients.

Conformational and biochemical differences in the TCR.CD3 complex of CD8(+) versus CD4(+) mature lymphocytes revealed in the absence of CD3gamma

Mature CD4(+) and CD8(+) T lymphocytes are believed to build and express essentially identical surface alphabeta T-cell receptor-CD3 (TCR.CD3) complexes. However, TCR.CD3 expression has been shown to be more impaired in CD8(+) cells than in CD4(+) cells when CD3gamma is absent in humans or mice. We have addressed this paradox by performing a detailed phenotypical and biochemical analysis of the TCR.CD3 complex in human CD3gamma-deficient CD8(+) and CD4(+) T cells. The results indicated that the membrane TCR.CD3 complex of CD8(+) T lymphocytes was conformationally different from that of CD4(+) lymphocytes in the absence of CD3gamma. In addition, CD8(+), but not CD4(+), CD3gamma-deficient T lymphocytes were shown to contain abnormally glycosylated TCRbeta proteins, together with a smaller, abnormal TCR chain (probably incompletely processed TCRalpha). These results suggest the existence of hitherto unrecognized biochemical differences between mature CD4(+) and CD8(+) T lymphocytes in the intracellular control of alphabetaTCR. CD3 assembly, maturation, or transport that are revealed when CD3gamma is absent. Such lineage-specific differences may be important in receptor-coreceptor interactions during antigen recognition.

Signaling through a CD3 gamma-deficient TCR/CD3 complex in immortalized mature CD4+ and CD8+ T lymphocytes

The biologic role of each CD3 chain and their relative contribution to the signals transduced through the TCR/CD3 complex and to downstream activation events are still controversial: they may be specialized or redundant. We have immortalized peripheral blood CD4+ and CD8+ T lymphocytes from a human selective CD3 gamma deficiency using Herpesvirus saimiri. The accessibility of the mutant TCR/CD3 complex to different Abs was consistently lower in immortalized CD8+ cells when compared with CD4+ cells, relative to their corresponding CD3 gamma-sufficient controls. Several TCR/CD3-induced downstream activation events, immediate (calcium flux), early (cytotoxicity and induction of surface CD69 or CD40L activation markers or intracellular TNF-alpha) and late (proliferation and secretion of TNF-alpha), were normal in gamma-deficient cells, despite the fact that their TCR/CD3 complexes were significantly less accessible than those of controls. In contrast, the accumulation of intracellular IL-2 or its secretion after CD3 triggering was severely impaired in gamma-deficient cells. The defect was upstream of protein kinase C activation because addition of transmembrane stimuli (PMA plus calcium ionophore) completely restored IL-2 secretion in gamma-deficient cells. These results suggest that the propagation of signals initiated at the TCR itself can result in a modified downstream signaling cascade with distinct functional consequences when gamma is absent. They also provide evidence for the specific participation of the CD3 gamma chain in the induction of certain cytokine genes in both CD4+ and CD8+ human mature T cells. These immortalized mutant cells may prove to be useful in isolating cytosolic signaling pathways emanating from the TCR/CD3 complex.

Construction of retroviral vectors carrying human CD3 gamma cDNA and reconstitution of CD3 gamma expression and T cell receptor surface expression and function in a CD3 gamma-deficient mutant T cell line

CD3 gamma, a subunit of the T cell receptor-CD3 (TCR/CD3) complex, helps to support surface TCR/CD3 expression and participates in signal transduction for gene induction after antigen recognition by T lymphocytes, and in TCR/CD3 down-modulation. Humans with primary immunodeficiencies caused by inherited mutations in the CD3 gamma gene or in the gene encoding epsilon CD3é, another subunit of TCR/CD3 complex, have been previously reported. To develop a gene therapy protocol for CD3-deficient patients, CD3 gamma cDNA was orientationally inserted into two retroviral vectors (LNCX and LXSN), which resulted in recombinant vectors LNCG and LGSN, respectively. Two vector producer cell lines Am12/LNCG and Am12/LGSN were established from packaging cells GP+envAm12. Their mean viral titers were 6.5 x 10(6) and 2.0 x 10(7) cfu/ml, respectively, as shown by an improved retroviral vector production and transduction method that increases titers around five-fold over conventional methods. The presence of helper virus in vector stocks was tested by marker rescue assay and found to be < 1 cfu/ml. Southern blot analysis showed that multiple copies of the vectors were present in the genome of high-titer producers and that both vectors could transfer CD3 gamma cDNA into the genome of 3T3 cells. The vectors were used to correct in vitro a CD3 gamma-deficient Jurkat mutant cell line lacking TCR/CD3 expression and termed JGN (for Jurkat gamma negative). Both vectors increased TCR/CD3 expression in JGN (normally 2% using WT31 monoclonal antibody) to 34% and 37%, respectively, in G418-selected 3-week bulk cultures. Two clones from transduced JGN cells termed JGN/LNCG13 and JGN/LNCG15, with high TCR/CD3 expression (88% and 79%, respectively), were selected for further analyses. First, CD3 gamma protein reconstitution was demonstrated by immunoprecipitation. Second, interleukin-2 production after TCR/CD3 engagement and TCR/CD3 down-modulation in response to phorbol myristate acetate were shown to be comparable to wild-type Jurkat cells. We conclude that LNCG and LGSN may be useful for gene therapy purposes.

Herpesvirus saimiri immortalization of alpha beta and gamma delta human T-lineage cells derived from CD34+ intrathymic precursors in vitro

Herpesvirus saimiri (HVS), an agent that can infect many human cell types, has been shown to immortalize selectively TCR alpha beta + CD3+ T lymphocytes. Human T cell precursors defined as CD34+CD3-CD4-CD8- were isolated from thymic samples and exposed to HVS in the presence of either IL-2 or IL-7. Cultures lacking the virus were non-viable by day 15. Test cultures, in contrast, showed a sustained proliferative activity lasting > 5 months, allowing the phenotypical and molecular analysis of the cellular progeny. In the presence of IL-7, TCR alpha beta + cells with three different phenotypes (mainly CD4+CD8-, but also CD4+CD8+ and CD4-CD8+) were immortalized, whereas no TCR gamma delta + cells were recovered. Kinetic studies showed that the expansion of immortalized TCR alpha beta + cells was preceded by a gradual loss of CD34+ cells followed by a transient accumulation of two distinct cell subsets: first CD1+CD4+CD3- cells and then CD4+CD8+ thymocytes. This resembles early phenotypic changes occurring during normal intrathymic T cell development. In the presence of IL-2, in contrast, only TCR gamma delta + cells were immortalized (mainly CD4-CD8+, but also CD4-CD8-). The results show that HVS can be used to read the CD3+ cellular outcome of T cell differentiation assays, including gamma delta + CD4-CD8+, gamma delta + CD4-CD8-, alpha beta + CD4+CD8-, alpha beta + CD4-CD8+ and alpha beta + CD4+CD8+ T cells. A clear role for different cytokines (IL-2 for gamma delta + cells, IL-7 for alpha beta + cells) in early T cell commitment was also apparent.