Electrocatalytic on-site oxygenation for transplanted cell-based-therapies

Implantable cell therapies and tissue transplants require sufficient oxygen supply to function and are limited by a delay or lack of vascularization from the transplant host. Previous exogenous oxygenation strategies have been bulky and had limited oxygen production or regulation. Here, we show an electrocatalytic approach that enables bioelectronic control of oxygen generation in complex cellular environments to sustain engineered cell viability and therapy under hypoxic stress and at high cell densities. We find that nanostructured sputtered iridium oxide serves as an ideal catalyst for oxygen evolution reaction at neutral pH. We demonstrate that this approach exhibits a lower oxygenation onset and selective oxygen production without evolution of toxic byproducts. We show that this electrocatalytic on site oxygenator can sustain high cell loadings (>60k cells/mm3) in hypoxic conditions in vitro and in vivo. Our results showcase that exogenous oxygen production devices can be readily integrated into bioelectronic platforms, enabling high cell loadings in smaller devices with broad applicability.

Relevance and Feasibility of a Personalized Dietary Intervention in Older People with Meals-On-Wheels: A Randomized Controlled Pilot Trial

Objective

The present study aimed at assessing the feasibility and the effectiveness of a personalized dietary intervention in a meals-on-wheels service through a randomized controlled pilot trial.

Design

Sixty recipients of home-delivered meals (75% of women; 70-97 years old) were recruited and randomly assigned to a control and an experimental group and followed over a period of 4 months. In the experimental group, the nutritional status (Mini-Nutritional Assessment - MNA questionnaire), the food intake and the food preferences were measured for each participant. Based on this screening, participants were provided with dietary guidance and follow-up. Those at risk of malnutrition were proposed enriched home-delivered meals. Enrichment was set up considering food preferences of the participants.

Results

Looking at the whole sample at baseline, 80% (n=48/60) were at risk of malnutrition. Furthermore, 55% (n=33/60) ate less than 2/3 of their calorie and/or protein recommended allowances. In the experimental group, the intervention led to an increase of protein intakes and to a lower extent of calorie intake. In the control group, no significant changes were observed.

Conclusion

To conclude, this study suggests that providing dietary guidance and adding nutrient-dense food to meals while considering food preferences is feasible and may help older beneficiaries of meals-on-wheels to increase calorie and protein intake and improve their nutritional status. However, there is a need to develop products or recipes to enrich the meals of the elderly more efficiently to achieve the recommended allowance.

An Architecture for Autonomy

An autonomous robot offers a challenging and ideal field for the study of intelligent architectures. Autonomy within a rational be havior could be evaluated by the robot's effectiveness and robust ness in carrying out tasks in different and ill-known environments. It raises major requirements on the control architecture. Further more, a robot as a programmable machine brings up other archi tectural needs, such as the ease and quality of its specification and programming.

This article describes an integrated architecture that allows a mobile robot to plan its tasks—taking into account temporal and domain constraints, to perform corresponding actions and to con trol their execution in real-time—while being reactive to possible events. The general architecture is composed of three levels: a de cision level, an execution level, and a functional level. The latter is composed of modules that embed the functions achieving sensor- data processing and effector control. The decision level is goal and event driven, and it may have several layers, according to the application; their basic structure is a planner/supervisor pair that enables the architecture to integrate deliberation and reaction.

The proposed architecture relies naturally on several representa tions, programming paradigms, and processing approaches, which meet the precise requirements that are specified for each level. The authors have developed proper tools to meet these specifications and implement each level of the architecture: a temporal planner, IxTeT; a procedural system for task refinement and supervision, PRS; Kheops for the reactive control of the functional level, and GenoM for the specification and integration of modules at that level Validation of the temporal and logical properties of the reactive parts of the system, through these tools, are presented.

Instances of the proposed architecture have been integrated into several indoor and outdoor robots. Examples from real-world ex perimentations are provided and analyzed.

Langerin+ dendritic cells are responsible for LPS-induced reactivation of allergen-specific Th2 responses in postasthmatic mice

Allergic asthma is a T cell-dependent inflammatory lung disease that results from complex interactions between genetic predisposition and environmental factors, including exposure to lipopolysaccharide (LPS). In this study, we have shown that airway LPS exposure was sufficient to induce airway hyperreactivity (AHR) and eosinophil recruitment in mice that had previously experienced an acute episode of allergic asthma. LPS-induced disease reactivation depended on the activation of allergen-specific CD4(+) T cells by a subset of lung langerin(+) dendritic cells (DCs) that retained the allergen. Upon LPS exposure, migration of langerin(+) DCs from lungs to draining lymph nodes increased and LPS-exposed langerin(+) DCs instructed CD4(+) T cells toward a T helper (Th) 2 response. Selective depletion of langerin(+) DCs prevented LPS-induced eosinophil recruitment and T-cell activation, further demonstrating a critical role for langerin(+) DCs in disease reactivation. This finding provides a possible explanation for the subclinical worsening of asthmatics following exposure to low-dose LPS.

The oral administration of bacterial extracts prevents asthma via the recruitment of regulatory T cells to the airways

The prevalence of asthma has steadily increased during the last decade, probably as the result of changes in the environment, including reduced microbial exposure during infancy. Accordingly, experimental studies have shown that deliberate infections with live pathogens prevent the development of allergic airway diseases in mice. Bacterial extracts are currently used in children suffering from repeated upper respiratory tract infections. In the present study, we have investigated whether bacterial extracts, commercially available as Broncho-Vaxom (BV), could prevent allergic airway disease in mice. Oral treatment with BV suppressed airway inflammation through interleukin-10 (IL-10)-dependent and MyD88 (myeloid differentiation primary response gene (88))-dependent mechanisms and induced the conversion of FoxP3 (forkhead box P3)(-) T cells into FoxP3(+) regulatory T cells. Furthermore, CD4(+) T cells purified from the trachea of BV-treated mice conferred protection against airway inflammation when adoptively transferred into sensitized mice. Therefore, treatment with BV could possibly be a safe and efficient strategy to prevent the development of allergic diseases in children.

Breast milk immune complexes are potent inducers of oral tolerance in neonates and prevent asthma development

Allergic asthma is a chronic lung disease resulting from an inappropriate T helper (Th)-2 response to environmental antigens. Early tolerance induction is an attractive approach for primary prevention of asthma. Here, we found that breastfeeding by antigen-sensitized mothers exposed to antigen aerosols during lactation induced a robust and long-lasting antigen-specific protection from asthma. Protection was more profound and persistent than the one induced by antigen-exposed non-sensitized mothers. Milk from antigen-exposed sensitized mothers contained antigen-immunoglobulin (Ig) G immune complexes that were transferred to the newborn through the neonatal Fc receptor resulting in the induction of antigen-specific FoxP3(+) CD25(+) regulatory T cells. The induction of oral tolerance by milk immune complexes did not require the presence of transforming growth factor-beta in milk in contrast to tolerance induced by milk-borne free antigen. Furthermore, neither the presence of IgA in milk nor the expression of the inhibitory FcgammaRIIb in the newborn was required for tolerance induction. This study provides new insights on the mechanisms of tolerance induction in neonates and highlights that IgG immune complexes found in breast milk are potent inducers of oral tolerance. These observations may pave the way for the identification of key factors for primary prevention of immune-mediated diseases such as asthma.

International institutions, global health initiatives and the challenge of sustainability: lessons from the Brazilian AIDS programme

The sustainability of successful public health programmes remains a challenge in low and middle income settings. These programmes are often subjected to mobilization-demobilization cycle. Indeed, political and organizational factors are of major importance to ensure this sustainability. The cooperation between the World Bank and the Brazilian AIDS programme highlights the role of international institutions and global health initiatives (GHI), not only to scale up programmes but also to guarantee their stability and sustainability, at a time when advocacy is diminishing and vertical programmes are integrated within health systems. This role is critical at the local level, particularly when economic crisis may hamper the future of public health programmes. Political and organizational evolution should be monitored and warnings should trigger interventions of GHI before the decline of these programmes.

Gene transfer of RANTES and MCP-1 chemokine antagonists prolongs cardiac allograft survival

Vascularized organ allografts are rapidly destroyed by host immune cells that are recruited along chemokine gradients. Among chemokines, Regulated on Activation, Normal T-cell Expressed and Secreted (RANTES) CC chemokine ligand (CCL5) and monocyte chemoattractant protein (MCP)-1 (CCL2) are upregulated in rejecting cardiac allografts. To antagonize these chemokines, we constructed adenoviral vectors expressing NH(2)-terminal deletion (8ND) mutants of the respective genes. Using the F344-to-LEW rat model, intragraft gene transfer of chemokine analogs prolonged cardiac allograft survival from 10.1+/-0.7 and 10.4+/-0.7 days using non-coding adenovirus and vehicle alone, respectively, to 17.0+/-0.7 days for 8ND-RANTES (P<0.001) and 14.2+/-0.8 days for 8ND-MCP-1 (P<0.01). 8ND-RANTES reduced graft infiltration by monocytes/macrophages, cluster of differentiation (CD) 8alpha(+) and T-cell receptor alphabeta(+) cells, while 8ND-MCP-1 reduced monocytes/macrophages. In mixed leukocyte reactions in vitro, proliferation of host lymphocytes from regional lymph nodes in response to donor splenocytes was unaffected by 8ND-RANTES gene transfer. Using a two-gene approach, the contribution of 8ND-MCP-1 was negligible, consistent with available evidence that 8ND-RANTES inhibits both RANTES and MCP-1 activities. 8ND-RANTES gene transfer and a short course of low-dose cyclosporine A synergistically prolonged graft survival to 37.8+/-5.5 vs 15.4+/-0.5 days with cyclosporine alone (P<0.001). These results suggest a role for anti-chemokine gene therapy as an adjuvant therapy in heart transplantation.

Association between the A-2518G polymorphism in the monocyte chemoattractant protein-1 gene and insulin resistance and Type 2 diabetes mellitus

AIMS/HYPOTHESIS

The molecular mechanisms of obesity-related insulin resistance are incompletely understood. Macrophages accumulate in adipose tissue of obese individuals. In obesity, monocyte chemoattractant protein-1 (MCP-1), a key chemokine in the process of macrophage accumulation, is overexpressed in adipose tissue. MCP-1 is an insulin-responsive gene that continues to respond to exogenous insulin in insulin-resistant adipocytes and mice. MCP-1 decreases insulin-stimulated glucose uptake into adipocytes. The A-2518G polymorphism in the distal regulatory region of MCP-1 may regulate gene expression. The aim of this study was to investigate the impact of this gene polymorphism on insulin resistance.

METHODS

We genotyped the Ludwigshafen Risk and Cardiovascular Health (LURIC) cohort ( n=3307). Insulin resistance, estimated by homeostasis model assessment, and Type 2 diabetes were diagnosed in 803 and 635 patients respectively.

RESULTS

Univariate analysis revealed that plasma MCP-1 levels were significantly and positively correlated with WHR ( p=0.011), insulin resistance ( p=0.0097) and diabetes ( p<0.0001). Presence of the MCP-1 G-2518 allele was associated with decreased plasma MCP-1 ( p=0.017), a decreased prevalence of insulin resistance (odds ratio [OR]=0.82, 95% CI: 0.70-0.97, p=0.021) and a decreased prevalence of diabetes (OR=0.80, 95% CI: 0.67-0.96, p=0.014). In multivariate analysis, the G allele retained statistical significance as a negative predictor of insulin resistance (OR=0.78, 95% CI: 0.65-0.93, p=0.0060) and diabetes (OR=0.80, 95% CI: 0.66-0.96, p=0.018).

CONCLUSIONS/INTERPRETATION

In a large cohort of Caucasians, the MCP-1 G-2518 gene variant was significantly and negatively correlated with plasma MCP-1 levels and the prevalence of insulin resistance and Type 2 diabetes. These results add to recent evidence supporting a role for MCP-1 in pathologies associated with hyperinsulinaemia.

Skewed maturation of memory HIV-specific CD8 T lymphocytes

Understanding the lineage differentiation of memory T cells is a central question in immunology. We investigated this issue by analysing the expression of the chemokine receptor CCR7, which defines distinct subsets of naive and memory T lymphocytes with different homing and effector capacities and antiviral immune responses to HIV and cytomegalovirus. Ex vivo analysis of the expression of CD45RA and CCR7 antigens, together with in vitro analysis of the cell-division capacity of different memory CD8+ T-cell populations, identified four subsets of HIV- and CMV-specific CD8+ T lymphocytes, and indicated the following lineage differentiation pattern: CD45RA+ CCR7+ --> CD45RA- CCR7+ --> CD45RA- CCR7- --> CD45RA+ CCR7-. Here we demonstrate through analysis of cell division (predominantly restricted to the CCR7+ CD8+ T-cell subsets) that the differentiation of antigen-specific CD8+ T cells is a two-step process characterized initially by a phase of proliferation largely restricted to the CCR7+ CD8+ cell subsets, followed by a phase of functional maturation encompassing the CCR7- CD8+ cell subsets. The distribution of these populations in HIV- and CMV-specific CD8+ T cells showed that the HIV-specific cell pool was predominantly (70%) composed of pre-terminally differentiated CD45RA- CCR7- cells, whereas the CMV-specific cell pool consisted mainly (50%) of the terminally differentiated CD45RA+ CCR7- cells. These results demonstrate a skewed maturation of HIV-specific memory CD8+ T cells during HIV infection.

Virological and immunological characteristics of HIV treatment failure

BACKGROUND

Resistance to antiretroviral treatment is prevalent. There is limited knowledge of the determinants of disease evolution in subjects infected with multidrug-resistant HIV (MDR-HIV).

METHODS

Infectivity, replication, chemokine receptor usage, and env, gag, protease and reverse transcriptase sequence analysis was performed for MDR-HIV isolates from 14 HIV-infected individuals and compared to wild-type HIV isolates from individuals naive to antiretroviral treatment. Expression of CD45RO/RA, Ki67 and interferon-gamma and CD4 proliferative response to various antigens was determined for individuals infected with MDR-HIV and compared to that in individuals with optimal suppression of viral replication.

RESULTS

Infectivity and replication are diminished for various MDR-HIV isolates, usually in the context of an increase in CD4 and CD4+CD45RA+ T-cell counts. However, a number of MDR-HIV isolates are associated with high in vivo viraemia and pronounced immunosuppression, and display in vitro levels of infectivity and replication comparable to those of wild-type strains. No specific genetic sequence or chemokine receptor usage predicted the fitness of an MDR isolate.

CONCLUSIONS

Despite the biological diversity of resistant viruses and the range of host responses observed, our descriptive analysis indicates that viral factors play a role in determining the degree of immune damage observed in the context of MDR-HIV infection.

Effects of mycophenolic acid on human immunodeficiency virus infection in vitro and in vivo

Mycophenolic acid, a selective inhibitor of the de novo synthesis of guanosine nucleotides in T and B lymphocytes, has been proposed to inhibit human immunodeficiency virus (HIV) replication in vitro by depleting the substrate (guanosine nucleotides) for reverse transcriptase. Here we show that mycophenolic acid induced apoptosis and cell death in a large proportion of activated CD4+ T cells, thus indicating that it may inhibit HIV infection in vitro by both virological mechanisms and immunological mechanisms (depletion of the pool of activated CD4+ T lymphocytes). Administration of mycophenolate mophetil, the ester derivate of mycophenolic acid, to HIV-infected subjects treated with anti-retroviral therapy and with undetectable viremia resulted in the reduction of the number of dividing CD4 + and CD8+ T cells and in the inhibition of virus isolation from purified CD4+ T-cell populations. Based on these results, the potential use of mycophenolate mophetil in the treatment of HIV infection deserves further investigation in controlled clinical trials.

Long-term kinetics of T cell production in HIV-infected subjects treated with highly active antiretroviral therapy

The long-term kinetics of T cell production following highly active antiretroviral therapy (HAART) were investigated in blood and lymph node in a group of HIV-infected subjects at early stage of established infection and prospectively studied for 72 wk. Before HAART, CD4 and CD8 T cell turnover was increased. However, the total number of proliferating CD4(+) T lymphocytes, i.e., CD4(+)Ki67(+) T lymphocytes, was not significantly different in HIV-infected (n = 73) and HIV-negative (n = 15) subjects, whereas proliferating CD8(+)Ki67(+) T lymphocytes were significantly higher in HIV-infected subjects. After HAART, the total body number of proliferating CD4(+)Ki67(+) T lymphocytes increased over time and was associated with an increase of both naive and memory CD4(+) T cells. The maximal increase (2-fold) was observed at week 36, whereas at week 72 the number of proliferating CD4(+) T cells dropped to baseline levels, i.e., before HAART. The kinetics of the fraction of proliferating CD4 and CD8 T cells were significantly correlated with the changes in the total body number of these T cell subsets. These results demonstrate a direct relationship between ex vivo measures of T cell production and quantitative changes in total body T lymphocyte populations. This study provides advances in the delineation of the kinetics of T cell production in HIV infection in the presence and/or in the absence of HAART.

Sampling lymphoid tissue cells by ultrasound-guided fine needle aspiration of lymph nodes in HIV-infected patients. Swiss HIV Cohort Study

OBJECTIVE

To establish the feasibility of using ultrasound-guided lymph node needle aspiration as a means to obtain lymphoid tissue cells for the determination of a series of immunologic and virologic measures in HIV-infected patients.

DESIGN

First, a comparison of the characteristics of cell populations obtained by simultaneous needle aspiration and standard excisional biopsy in six patients. Second, use of lymph node needle aspiration to assess longitudinally T-cell subset changes in patients initiating highly effective antiretroviral treatment.

METHODS

T-cell subsets (CD4 and CD8) and percentage Ki67+ cycling T cells were measured in lymph node cell populations harvested by ultrasound-guided aspiration or standard biopsy by flow cytometry. Cellular RNA content was assessed by a modification of the Roche Amplicor HIV-1 Monitor test.

RESULTS

CD4 and CD8 T-cell percentage and HIV RNA cell content of lymph node cell suspensions obtained from the simultaneous performance of ultrasound-guided needle aspiration and excisional biopsy in the same patients were correlated (n = 6). Among the 87 aspiration sessions reported here, mononuclear cell suspensions were obtained in 100% of the sessions, in numbers ranging between 4x10(4) to 6.7x10(6) cells (median: 7x10(5)). This limited number of cells did not allow to perform all type of analyses in all patients. By prioritizing the cells for the determination of T-cell subsets and proliferation rate, this approach was instrumental for demonstrating the normalization of the T-cell subset ratio and the kinetic of normalization of proliferating rates of CD4 and CD8 T cells, as well as the decrease in HIV-1 viral load in the lymph node following HAART initiation.

CONCLUSION

Ultrasound-guided aspiration appears to be a non-invasive and ad libitum, safe and repeatable procedure for the longitudinal monitoring of changes in lymph nodes.

T cell regeneration in HIV-infected subjects under highly active antiretroviral therapy (review)

The initial idea that high amounts of cytopathic virus produced everyday can drive high CD4+ T cell production seemed logical and explained the progressive CD4+ T cell depletion observed in HIV-infected subjects. It was hypothesized that the CD4+ T lymphocyte production was increased up to 70-fold in HIV-infected subjects. Determination of the CD4+ T cell production was based on the kinetics of CD4+ T cell recovery following initiation of highly active antiretroviral therapy (HAART). However, this analysis is limited by: i) the assumption that blood CD4+ T cells are representative of the lymph node T cells; and ii) the lack of estimates of CD4+ T lymphocyte turnover in healthy HIV-negative subjects. Several immunologists have expressed caution regarding the assumptions used in modeling CD4+ T cell dynamics. Recent findings clearly show that blood is not representative of lymphoid tissues and invalidate the conclusion of high CD4 turnover drawn from blood studies on HIV-infected subjects. Indeed, when blood and lymph node compartments are considered together, we find that HIV-infected subjects naive to antiretroviral have similar or lower CD4+ T cell production, as compared to healthy subjects. This observation suggests an impaired T cell renewal capacity in HIV-1 infected patients.

Normal T-cell telomerase activity and upregulation in human immunodeficiency virus-1 infection

In human immunodeficiency virus (HIV)-1 infection, decrease of telomere length is mainly found in CD8(+) T cells and not in CD4(+) T cells. Telomerase, a ribonucleoprotein enzyme that can synthesize telomeric sequence onto chromosomal ends, can compensate for telomere loss. Here, we investigated if telomerase activity could explain differential telomere loss of CD4(+) and CD8(+) T cells in HIV-1 infection. Telomerase activity was higher in CD8(+) than in CD4(+) T cells from HIV-infected patients, but still in the same range as in healthy controls, and upregulation after stimulation was comparable to normal. Telomerase activity in lymph node CD4(+) and CD8(+) T cells from HIV-infected patients was in the same range as that in CD4(+) and CD8(+) T cells from peripheral blood (PB) and was normal in unseparated bone marrow cells. Thus, our study did not provide evidence for compartmentalized elongation of telomeres in HIV infection. In patients treated with reverse transcriptase inhibitors, telomerase activity was inhibited, but this did not lead to accelerated loss of telomere length in vivo. Thus, differential telomere loss in CD4(+) and CD8(+) T cells in HIV-1 infection cannot be explained by telomerase activity.

Limited CD4+ T-cell renewal in early HIV-1 infection: effect of highly active antiretroviral therapy

We show that the fraction of proliferating CD4+ lymphocytes is similar in HIV-infected subjects in the early stage of disease and in HIV-negative subjects, whereas the fraction of proliferating CD8+ lymphocytes is increased 6.8-fold in HIV-infected subjects. After initiation of antiviral therapy, there is a late increase in proliferating CD4+ T cells associated with the restoration of CD4+ T-cell counts. These results provide strong support for the idea of limited CD4+ T-cell renewal in the early stage of HIV infection and indicate that after effective suppression of virus replication, the mechanisms of CD4+ T-cell production are still functional in early HIV infection.

Analysis of the contact sites on the CD4 molecule with class II MHC molecule: co-ligand versus co-receptor function

The CD4 molecule interacts with the alpha2 and beta2 domains of the MHC class II molecules. However, the class II contact sites on CD4 are less clear. Involvement of different regions throughout D1, D2, and D3 domains have been suggested. To further delineate the class II MHC contact sites on CD4, a crystal structure-informed mutagenesis was performed. Alanine scan mutants were generated for exposed residues located throughout D1 and the FG loop of D2, and in the "hinge-like" region, a short and flexible region between D2 and D3. Mutants were tested in a co-ligand (Dd stimulation) and a co-receptor (staphylococcal enterotoxin B stimulation) assay. In the co-ligand assay, TCR and CD4 interact with two distinct ligands (Dd or HLA-DR), while in the co-receptor assay both molecules interact with the same ligand, namely HLA-DR. Results show that residues from both lateral faces of D1 and the FG loop of D2 are implicated in interaction with class II, although a bigger surface of CD4 was involved in co-receptor compared with co-ligand function. The potential involvement of residues on both the top and two side faces of CD4 is consistent with a bivalent model, which involves the interaction between a single CD4 and two class II molecules. Alternatively, our results can be interpreted with a model of a specifically organized CD4 and/or class II oligomerization event. Finally, results from the hinge region mutants revealed a very important role in maintaining the overall structural integrity of CD4, its topology, and function.

Analysis of the contact sites on the CD4 molecule with class II MHC molecule: co-ligand versus co-receptor function

The CD4 molecule interacts with the alpha2 and beta2 domains of the MHC class II molecules. However, the class II contact sites on CD4 are less clear. Involvement of different regions throughout D1, D2, and D3 domains have been suggested. To further delineate the class II MHC contact sites on CD4, a crystal structure-informed mutagenesis was performed. Alanine scan mutants were generated for exposed residues located throughout D1 and the FG loop of D2, and in the "hinge-like" region, a short and flexible region between D2 and D3. Mutants were tested in a co-ligand (Dd stimulation) and a co-receptor (staphylococcal enterotoxin B stimulation) assay. In the co-ligand assay, TCR and CD4 interact with two distinct ligands (Dd or HLA-DR), while in the co-receptor assay both molecules interact with the same ligand, namely HLA-DR. Results show that residues from both lateral faces of D1 and the FG loop of D2 are implicated in interaction with class II, although a bigger surface of CD4 was involved in co-receptor compared with co-ligand function. The potential involvement of residues on both the top and two side faces of CD4 is consistent with a bivalent model, which involves the interaction between a single CD4 and two class II molecules. Alternatively, our results can be interpreted with a model of a specifically organized CD4 and/or class II oligomerization event. Finally, results from the hinge region mutants revealed a very important role in maintaining the overall structural integrity of CD4, its topology, and function.

Mutations in human CD4 impair the functional interaction with different human and mouse class II isotypes and alleles

The structure-function of the CD4-class II MHC interaction was investigated. Two functional assays were used to assess the responses of the 3DT52.5.8 murine T cell hybridoma expressing human CD4 (h-CD4) or murine CD4 (m-CD4). First, we determined the responses of the CD4+ and CD4-effector cells toward DAP-3 cells co-expressing the cognate alloantigen H-2Dd together with several human (DRw52b, DR4-Dw4, DR2A, and DPw2) and murine (I-Ab, I-Ak, IA alpha b I-A beta k and I-Ek) class II alleles and isotypes. We found that h-CD4 and m-CD4 strongly enhance the T cell response to H-2Dd, demonstrating that interspecies CD4/class II interactions occur efficiently. Furthermore, mutations in h-CD4 at positions 19, 89, and 165 markedly reduced the interaction with both human class II and mouse class II, indicating that the structural features of this cross-species interaction are strongly conserved. This was further supported by the finding that a h-CD4 deletion mutant (deletion F43-S49) interacted with both human and murine class II. Moreover, as 3DT cells express the responsive V beta element for the bacterial superantigen staphylococcal enterotoxin B, a co-receptor assay was conducted. DAP-3 cells expressing only class II molecules were used as APCs to present staphylococcal enterotoxin B to h-CD4+ and m-CD4+ T cells. h-CD4 and m-CD4 were able to enhance the T cell response to staphylococcal enterotoxin B, further demonstrating the conservation of the CD4-class II MHC interaction.

Mutations in human CD4 impair the functional interaction with different human and mouse class II isotypes and alleles

The structure-function of the CD4-class II MHC interaction was investigated. Two functional assays were used to assess the responses of the 3DT52.5.8 murine T cell hybridoma expressing human CD4 (h-CD4) or murine CD4 (m-CD4). First, we determined the responses of the CD4+ and CD4-effector cells toward DAP-3 cells co-expressing the cognate alloantigen H-2Dd together with several human (DRw52b, DR4-Dw4, DR2A, and DPw2) and murine (I-Ab, I-Ak, IA alpha b I-A beta k and I-Ek) class II alleles and isotypes. We found that h-CD4 and m-CD4 strongly enhance the T cell response to H-2Dd, demonstrating that interspecies CD4/class II interactions occur efficiently. Furthermore, mutations in h-CD4 at positions 19, 89, and 165 markedly reduced the interaction with both human class II and mouse class II, indicating that the structural features of this cross-species interaction are strongly conserved. This was further supported by the finding that a h-CD4 deletion mutant (deletion F43-S49) interacted with both human and murine class II. Moreover, as 3DT cells express the responsive V beta element for the bacterial superantigen staphylococcal enterotoxin B, a co-receptor assay was conducted. DAP-3 cells expressing only class II molecules were used as APCs to present staphylococcal enterotoxin B to h-CD4+ and m-CD4+ T cells. h-CD4 and m-CD4 were able to enhance the T cell response to staphylococcal enterotoxin B, further demonstrating the conservation of the CD4-class II MHC interaction.

HLA-DR polymorphism affects the interaction with CD4

Major histocompatibility complex (MHC) class II molecules are highly polymorphic and bind peptides for presentation to CD4+ T cells. Functional and adhesion assays have shown that CD4 interacts with MHC class II molecules, leading to enhanced responses of CD4+ T cells after the activation of the CD4-associated tyrosine kinase p56lck. We have addressed the possible contribution of allelic polymorphism in the interaction between CD4 and MHC class II molecules. Using mouse DAP-3-transfected cells expressing different isotypes and allelic forms of the HLA-DR molecule, we have shown in a functional assay that a hierarchy exists in the ability of class II molecules to interact with CD4. Also, the study of DR4 subtypes minimized the potential contribution of polymorphic residues of the peptide-binding groove in the interaction with CD4. Chimeras between the DR4 or DR1 molecules, which interact efficiently with CD4, and DRw53, which interacts poorly, allowed the mapping of polymorphic residues between positions beta 180 and 189 that can exert a dramatic influence on the interaction with CD4.

[Inequities in health policies: the Latin American case]

Four points relating to the iniquities of the health services are brought out. In the first, the economic crisis the region has been going through during recent decades, is discussed and the contention that the tendency to an overall improvement of the living conditions has not been deeply affected by this crisis is questioned. In the second the characteristics of the Latin-American process of development, marked by the deepening of the iniquities is examined. In the third an analysis of the pattern of social protection in the region is presented and in the last two polar models for the reformation of this pattern are discussed.

Mutational analysis of the interaction between CD4 and class II MHC: class II antigens contact CD4 on a surface opposite the gp120-binding site

Using functional and adhesion assays, we have studied the ability of 30 human CD4 mutants to interact with class II major histocompatibility complex (MHC) molecules and also with gp120 from human immunodeficiency virus. The mutants cover the four domains (D1-D4) of CD4 and include several single-site substitutions. Analysis of the results, in the context of the CD4 crystal structure, shows that mutations that affect the interaction with class II MHC molecules are located on three exposed loops from CD4 domains 1 and 2. The specifically implicated residues, 19, 89, and 165, are separated from one another by 9 A, 24 A, and 24 A on one face of the CD4 molecule. Moreover, the class II binding site does not include residues 43 to 49 of the CD4 molecule, a region on an opposite face known to be involved in the binding of gp120.

The MHC-binding and gp120-binding functions of CD4 are separable

CD4 is a cell surface glycoprotein that is thought to interact with nonpolymorphic determinants of class II major histocompatibility (MHC) molecules. CD4 is also the receptor for the human immunodeficiency virus (HIV), binding with high affinity to the HIV-1 envelope glycoprotein, gp120. Homolog-scanning mutagenesis was used to identify CD4 regions that are important in class II MHC binding and to determine whether the gp120 and class II MHC binding sites of CD4 are related. Class II MHC binding was abolished by mutations in each of the first three immunoglobulin-like domains of CD4. The gp120 binding could be abolished without affecting class II MHC binding and vice versa, although at least one mutation examined reduced both functions significantly. These findings indicate that, while there may be overlap between the gp120 and class II MHC binding sites of CD4, these sites are distinct and can be separated. Thus it should be possible to design CD4 analogs that can block HIV infectivity but intrinsically lack the ability to affect the normal immune response by binding to class II MHC molecules.

A positive signal is transduced via surface CD4 molecules

We have previously reported on the identification of a monoclonal antibody (mAb) directed against the human CD4 antigen which is capable of activating CD4+ peripheral blood T cells in the absence of other stimuli. In the present study, we extended these findings by demonstrating that the mAb, termed B66, was able to induce the production of interleukin-2 in murine T-cell hybridoma transfectants expressing the human CD4 glycoprotein. Moreover, we found that incubation of Jurkat cells with mAb B66 resulted in the nearly complete disappearance of both CD4 and CD3 from the cell surface, whereas modulation of CD4, but not CD3, was observed after incubation with a non-stimulatory anti-CD4 mAb. Similar results were obtained in modulation experiments using human CD4-expressing murine transfectants. It is thus conceivable that the stimulatory activity of anti-CD4 mAb B66 may be associated with an effect on the CD3 molecular complex. While the biochemical basis for the unique stimulatory activity of mAb B66 has yet to be defined, these findings provide direct evidence that cross-linking of CD4 alone may cause T-cell activation, thus supporting the notion that this glycoprotein can transduce independent positive signals upon binding to class II major histocompatibility complex molecules.

Analysis of some functions of maternal and cord blood lymphocytes

Various immunological investigations were performed on lymphocytes from pregnant women at the time of delivery and on cord blood cells. The results thus obtained show that: -- An appreciable number of in vitro responses to various antigens is observed among the cord blood specimens. They correlate with a corresponding positive test with the maternal blood. -- The stimulability of maternal lymphocytes to PHA and Con-A is within normal limits, whereas cord blood lymphocytes respond poorly to these two mitogens. -- The percentage of rosette forming T cells is very low in the cord blood and normal in maternal blood. -- The MLC in maternal-cord blood co-cultured show a significant inhibitory effect due to cord blood cells distinct from maternal cells. -- Cord blood lymphocytes show a normal capacity to elaborate the two lymphocytes LIF and LMF. On the other hand, the capacity of maternal lymphocytes to synthetize LMF seems to be strongly impaired. -- An inhibitory factor for PHA-stimulated mitogenic response is present in maternal serum whereas it is absent in the cord serum. -- Maternal serum IgG is significantly decreased when compared to that of normal controls. The values for IgM, IgA and IgE are within normal ranges. The cord blood IgG is slightly higher than that of the mothers. The values for IgM, IgA and IgE are very low and irregularly present.