Costimulation of CD4+ and CD8+ T cells through CD26: the ADA-binding epitope is not essential for complete signaling.

It was previously shown that CD26 (DPP IV, EC 3.4.14.5) is a binding site for adenosine deaminase (ADA, EC 3.5.4.4) on T cells and that costimulation by some anti-CD26 monoclonal antibodies (mAbs) and anti-CD3 induces CD4+ T cell proliferation. The CD26 epitopes involved in costimulation, the precise sequence of the events preceding proliferation, and the response of CD8+ compared with CD4+ T cells to CD26 were not extensively studied. We therefore compared the effects of the novel TA5.9 anti-CD26 mAb, recognizing an ADA-binding epitope, and the clearly distinct anti-Ta1 reference anti-CD26 mAb for their costimulatory properties in various T cell subsets. Both purified CD4+ and CD8+ T cells proliferated upon costimulation with anti-CD3 and either anti-CD26 mAb, but anti-TA5.9 mAb induced a more potent response than anti-Ta1. Either anti-CD26 mAb, together with anti-CD3, caused a similar sequential up-regulation of CD69, CD25 (IL-2R alpha), and CD71 (transferrin receptor) expression on CD4+ and CD8+ T cells. The activation markers appeared faster on the CD45R0+ than on the CD45R0- subsets. After costimulation, CD4+ T cell cultures contained significant amounts of the Th1 cytokines IL-2, interferon-gamma (IFN-gamma), and tumor necrosis factor-alpha (TNF-alpha). In CD8+ T cell cultures relatively more IFN-gamma and TNF-alpha but almost no IL-2 was measured after triggering of CD3 and CD26. Our data demonstrate that the recognition of the ADA-binding epitope is not a prerequisite for the costimulatory capacity of anti-CD26 mAbs. Both CD4+ and CD8+ T cells and their CD45R0- and CD45R0+ subsets are sensitive to various aspects of activation via CD26, but the magnitude and/or kinetics differ according to the anti-CD26 used and the T cell subset studied.

Increased cytolytic T lymphocyte activity and decreased B7 responsiveness are associated with CD28 down-regulation on CD8+ T cells from HIV-infected subjects.

The CD28 receptor on CD4+ and CD8+ T cells interacts with B7 molecules on antigen-presenting cells (APC) to generate essential costimulatory signals. The cytolytic potential of CD8+ T cells could be linked to CD28 expression. Since HIV induces dysfunction of both CD4+ and CD8+ T cells, we evaluated CD28 expression and function in both subsets during HIV infection. CD28 expression on CD8+ T cells from HIV+ subjects was strongly reduced in a disease stage-related fashion. CD28- CD8+ T cells preferentially expressed CD57 and CD11b, but lacked CD26 and IL-2R alpha. The CD8+ T cells from the patients showed a significantly reduced proliferative response to co-stimulation with cell-bound anti-CD3 and B7. Nevertheless, when stimulated with plate-fixed anti-CD3, CD8+ T cells from HIV-infected subjects proliferated normally, and normal levels of IL-2R alpha and transferrin-receptor could be induced on CD28- CD8+ T cells from the patients. In addition, stimulation with plate-fixed anti-CD3 induced proliferative responses in highly purified CD28- CD8+ T cells from both HIV- and HIV+ persons. Furthermore, the increased cytotoxic activity of peripheral blood mononuclear cells (PBMC) from HIV+ subjects, measured in an anti-CD3 redirected assay, was predominantly exerted by CD28- CD57+ T cells. CD4+ T cells from the patients showed a slight but significant CD28 down-regulation and were slightly hyporesponsive to B7 co-stimulation. Decrease of CD28 on CD8+ T cells from HIV+ subjects is associated with an impaired response to co-stimulation via B7. CD28- CD8+ T cells from seropositives, however, are not completely inert, since they contain in vivo activated CTL and they can be additionally activated through a B7-independent stimulation.

Selective increase of activation antigens HLA-DR and CD38 on CD4+ CD45RO+ T lymphocytes during HIV-1 infection.

Infection with HIV results in a progressive depletion of CD4+ T cells and leads to significant in vivo lymphocyte phenotype changes. In this regard, the expression of HLA-DR and CD38 on CD8+ T cells has been shown to increase dramatically with disease progression. We investigated the expression of both activation markers on CD4+ T cells in HIV-1-infected subjects at different clinical stages of infection and compared the in vivo activation of CD4+ T cells with parameters of viral activity and CD8+ T cell activation. Fresh peripheral venous blood was obtained from 54 HIV-infected subjects and from 28 uninfected healthy controls. Three-colour immunophenotyping of the CD4+ T cell subset showed that the proportion of CD4+ T cells expressing HLA-DR (10% in HIV-negative controls) or CD38 (62% in HIV-negative controls) was higher in asymptomatic (P < 0.05 for CD38) and symptomatic (P < 0.001 for HLA-DR and CD38) HIV-infected subjects than in controls, whereas the proportion of CD4+ T cells expressing CD45RO (54% in controls) remained relatively unchanged. Simultaneous expression of HLA-DR and CD38 on CD4+ T cells increased from 2.3% in controls to 11% (P < 0.001) in asymptomatic and 22% (P < 0.001) in symptomatic HIV-infected subjects. This relative increase of CD38 and HLA-DR expression occurred mainly on CD4+ T cells co-expressing CD45RO. Changes in expression of HLA-DR and CD38 on CD4+ T cells correlated with similar changes on CD8+ T lymphocytes, with the presence of HIV antigen in the circulation, and with the disease stage of HIV infection.

Immunological comparison of HIV-1-, HIV-2- and dually-reactive women delivering in Abidjan, Côte d'Ivoire.

OBJECTIVES: To compare the basic immunological changes induced by HIV-1 and HIV-2 infection and to assess the immune status of subjects serologically reactive to both HIV-1 and HIV-2 (dually-reactive). DESIGN: Immune parameters were studied cross-sectionally in women delivering in Abidjan, Côte d'Ivoire, West Africa, where HIV-1 and HIV-2 are endemic. In this area, a significant number of sera from infected individuals are reactive to both HIV-1 and HIV-2. SUBJECTS AND METHODS: Two hundred and twenty-eight women delivering in a major maternity clinic were screened for HIV-1 and HIV-2 using an enzyme-linked immunosorbent assay. Seropositivity was confirmed by Western blot. The immune parameters studied were CD4+ and CD8+ lymphocyte subsets, immunoglobulin (Ig) serum levels, neopterin and beta 2-microglobulin (beta 2M) serum levels. RESULTS: Similar but less pronounced immune changes were present in HIV-2-reactive subjects compared with HIV-1- and dually-reactive subjects. The observed differences between the HIV-seropositive groups could not be explained by differences in age or disease stage but paralleled differences in the frequency of persistent generalized lymphadenopathy (PGL). The intermediate immune profile of HIV-2-reactives (between seronegatives and HIV-1- and dually-reactives) was most clearly reflected by the number of CD8+ lymphocytes, the CD4:CD8 ratio and the IgG serum level. Median neopterin and beta 2M levels, though significantly increased in all HIV-seropositive groups, did not differ significantly between HIV-2-, HIV-1- and dually-reactives. CONCLUSIONS: HIV-2 infection is associated with typical HIV-related immunological changes. Immunologically, dually-reactives resemble HIV-1-reactives more closely than HIV-2-reactive subjects.

[Urinary bilharziasis]. / La bilharziose urinaire.

A short account is given of present views on urinary schistosomiasis or bilharziasis. The incidence of infections is increasing in endemic areas of Africa and the near east, as a consequence of irrigation programs and hydroelectric power development. Urinary schistosomiasis is a disease of children and young adults. The serious consequences, obstructive uropathy due to more or less irreversible ureteral lesions, and cancer of the bladder, less directly related to the infection, appear but later in life. Diagnosis is still based on parasitology and serology but ultrasonography has proven to be an important means to evaluate the extent of lesions of the urinary tract, especially in developing countries. Praziquantel was a major development in the medical treatment and cures easily the infection. Some irreversible consequences have however to be treated surgically. Schistosomiasis is still an important cause of morbidity and mortality in medically backward endemic countries. The control of the disease aims at reducing morbidity and mortality, consequences of the infection, rather than to avoid infection itself. It is based on mass treatment of school age children, together with focal molluscacides at places where people have contacts with water. Vaccination will be available in the near future and will be a welcome addition to other control measures, but will not be able to interrupt transmission on its own. Only economic development will solve in the long term this social African problem.

HIV antigen detection in circulating immune complexes.

Various methods were evaluated for their effectiveness in releasing HIV antigen (Ag) from artificial immune complexes (IC) and from IC present in serum from HIV antibody (Ab) positive subjects. The most effective methods for recovering HIV Ag from IC were those which included a denaturation step to prevent reassociation of Ag with Ab. IC precipitation in 2.5% polyethylene glycol followed by acid treatment with 1 M glycine.HCl (pH 2) for 10 min at 70 degrees C in the presence of 0.05% SDS gave very satisfactory results. With this method, IC were detected in sera from HIV antibody positive Caucasian subjects at all stages of infection. After HIV IC dissociation, HIV Ag was detected in a significant number (8/17 or 47%) of asymptomatic subjects. IC were most prevalent during the late stages of infection. A substantial increase in HIV Ag positivity was also observed in 20 Senegalese HIV Ab positive sera. After HIV IC dissociation HIV antigen detection increased from 2/20 to 12/20. The relevance of IC detection is discussed.

Schistosomicidal effects of Pavetta owariensis and Harrisonia abyssinica in mice infected with Schistosoma mansoni.

The schistosomicidal properties of ethanol and acetone extracts of Pavetta owariensis and an ethanol extract of Harrisonia abyssinica were assessed in mice infected with Schistosoma mansoni. Spleen weight, number of adult worms and eggs and size of liver granulomas were the main parameters studied. All P. owariensis extracts containing proanthocyanins were shown to cause a reduction in size of periovular granuloma formation in the liver. This effect was most pronounced with ethanol extracts of both "white bark" and "red bark" varieties of the plant. Acetone extracts of P. owariensis "red bark" variety, containing the highest concentration of proanthocyanins, caused a marked reduction of egg numbers in the liver and intestine whereas the ethanol extract of H. abyssinica proved to be inactive.

Immunohistochemical characterization of the mononuclear cells in the brain of the rat with an experimental chronic Trypanosoma brucei gambiense infection.

The distribution of T-cell subsets, B cells, and class II MHC antigens was examined within the CNS of rats chronically infected with Trypanosoma brucei gambiense, using appropriate mouse monoclonal antibodies. The mononuclear infiltrates of the leptomeninges and the perivascular areas (Virchow-Robin spaces) were composed of IgM-producing plasma cells and Mott cells and T-helper/inducer cells. Cells defined phenotypically as suppressor/cytotoxic T cells were rare. Anti-Ia reactive cells were also abundant in these inflammatory lesions and in the white matter, representing Ia-expressing neuroglial cells, B cells, activated T cells, and macrophages. The Ia-positive neuroglial cells, possibly acting as accessory cells, associated with numerous T-helper/inducer cells and cells from the B-cell lineage, suggest that a T-dependent B-cell immune response can be initiated within the CNS of rats with a chronic T. b. gambiense infection.

Immune complexes and Pseudomonas aeruginosa antibodies in cystic fibrosis.

Serum samples from 57 patients with cystic fibrosis were tested for the presence of IgG, IgA, IgM, IgE, and circulating immune complexes containing IgG, IgA, and IgM. Titres of class specific antibodies to Pseudomonas aeruginosa, and class specific antibodies to Ps aeruginosa in circulating immune complexes, were also measured. According to the Shwachman score the patients were divided into three clinical groups: group 1-moderate and severe disease, group 2-mild disease, and group 3-well. The results of the immunological investigations were correlated with the clinical state of the patients as assessed by the Shwachman score. Serum concentrations of IgG, IgA, and IgM were inversely correlated with the Shwachman score, but the differences between the groups were only significant for IgG and IgA. The same correlations were found for circulating immune complexes containing IgG and IgA. Antibodies to Ps aeruginosa could be detected in most of the patients' serum samples. IgA antibody specific to Ps aeruginosa was the most often raised, even in patients in group 3. It is therefore suggested that IgA antibody specific to Ps aeruginosa could be an early marker of colonisation by Ps aeruginosa and a sensitive measurement of infection with Ps aeruginosa in young children with cystic fibrosis. Moreover, in the circulating immune complexes, class specific antibodies to Ps aeruginosa were found in nearly half the patients. The highest titres of IgG and IgA antibodies specific to Ps aeruginosa in the circulating immune complexes were detected in the patients with the worst clinical state (group 1).

Role of IgM-rheumatoid factor interference in the determination of total serum IgE and IgE-containing circulating immune complexes.

IgM-rheumatoid factor (RF) interference in the determination of total serum IgE and IgE-containing circulating immune complexes (IgE-CIC) was studied by inhibition experiments in vitro comparing a new ELISA technique free of IgM-RF interference with more widely used RIA methods. It was shown that a considerable overestimation of the IgE content in CIC can exist when high levels of IgM-RF are present in the same serum. The clinical part of this study revealed a dramatic fall in prevalence of IgE-CIC in patients with rheumatoid arthritis (RA) with the ELISA technique, compared with the more conventional RIA method (respectively 1/20 compared to 12/20 positive for IgE-CIC). In these patients, there was a good correlation between the level of IgM-RF and the amount of IgE detected in the CIC by the RIA method (r = 0.87) whereas the RF-interference free ELISA method showed no correlation between these two parameters (r = 0.06). Total serum IgE determination with a solid phase RIA was also influenced by IgM-RF interference, whereas the PRIST method was not affected by the presence of IgM-RF. In conclusion, in patients with rheumatic diseases, IgE-assays using polyclonal rabbit or sheep anti-IgE antibodies are not appropriate and monoclonal anti-IgE antibodies that have been proved not to interfere with IgM-RF should be advocated.

A useful method for determining class-specific rheumatoid factors with computerized analyses of data.

A simple and sensitive enzyme-linked immunosorbent assay (ELISA) was developed to determine rheumatoid factors (RFs) of IgG, IgA and IgM class. Standardisation was performed with a standard reference serum for IgM-RF, calibrated according to the WHO preparation, and with the serum of a patient containing high levels of IgA- and IgG-RF. The sigmoidal shaped calibration curve was fitted with a computerized four parameter logistic model with simplified mathematical computations. This method provided to be more accurate for measuring RF levels, as judged by the smaller residuals, than logit or log-linear transformations. The considerable reduction in processing time, which is obtained by the computerized analysis of data, makes this method of class-specific RF determination suitable for routine analysis.

Neutrophil activation by IgE-containing circulating immune complexes of patients with connective tissue diseases.

In an earlier study, we reported IgE-containing circulating immune complexes (CICs) in 66.6% of the patients with rheumatoid arthritis who were studied, especially in those with extra-articular manifestations. The present study was undertaken to examine the possible role of these immune complexes in inflammatory cell activation. Twelve patients with classic or definite rheumatoid arthritis, two with primary Sjögren's syndrome, and three patients with systemic lupus erythematosus were studied. Of these 17 patients, 10 were IgE-containing CIC positive, and seven patients were IgE-containing CIC negative. Polyethylene glycol-precipitated IgE-containing CICs and IgG-containing CICs of these patients were coated on plastic wells and incubated with suspensions of neutrophils. As a parameter of cell activation, superoxide release (SOR) was measured by cytochrome C reduction in the supernatant after 30, 60, and 90 minutes. There was a significant SOR up to 38% of the zymosan control when IgE-containing CICs were incubated with neutrophils. Furthermore, there was a significant correlation between the level of IgE-containing CICs and the amount of SOR, but not between the level of IgG-containing CICs and the amount of SOR. These results suggest a possible role for IgE-containing CICs in the activation of inflammatory cells in connective tissue diseases.

Schistosoma mansoni: impaired clearance of model immune complexes consisting of circulating anodic antigen and monoclonal IgG1 in infected mice.

The clearance of schistosome-specific model immune complexes (IC) consisting of circulating anodic antigen (CAA), a gut-associated excretory-secretory antigen, and radiolabeled monoclonal antibody (IgG1) was investigated in mice with a light and heavy Schistosoma mansoni infection and in noninfected control animals. The size analysis of the in vitro prepared and injected IC, as determined by density gradient centrifugation, revealed a wide peak at 11S. In infected animals the injected IC were cleared at a significantly lower rate than in control mice. This was attributed to a decreased uptake of IC by the liver in infected mice. In heavily infected mice, 30 min after injection of 11S IC, 8S, 11S, and greater than 11S IC were present in the serum, whereas only small 8S IC were detected in the serum of lightly infected animals and noninfected controls. Immune complexes were also present in the serum of heavily infected mice 30 min after injection of antibody and were detectable as 11S and greater than 11S IC. The importance of this study is twofold. First, these results show that schistosome-specific monoclonal antibodies can be used in the production of model immune complexes applicable in clearance studies. Second, our findings might be of importance when the possible pathogenicity of circulating IC in schistosomiasis is considered.

HLA studies of endemic African Kaposi's sarcoma patients and matched controls: no association with HLA-DR5.

In the search for a genetic factor involved in the etiology of Kaposi's sarcoma, several studies have recently focused on a significantly increased HLA determinant, DR5, as well as a decreased DR3, among patients with both the classical and the AIDS-related form of Kaposi's sarcoma. To test the consistency of this phenomenon, we analysed the frequencies of HLA immunogenetic markers in 23 histologically confirmed Kaposi's sarcoma patients from Central Africa, where this tumor is endemic, and a local sex- and tribe-matched control group. No definite association was observed for any of the HLA antigens, including DR5 and DR3. We were not able to support the hypothesis that the same HLA-associated immune susceptibility factors are involved in all types of Kaposi's sarcoma.