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Biomedical subjects

G Pantaleo

Publications and source records attributed to G Pantaleo.

125 records · Page 7Linked to original sources
PubMed1983

Quantitative assessment of the pool size and subset distribution of cytolytic T lymphocytes within human resting or alloactivated peripheral blood T cell populations.

In order to directly assess the distribution of cytolytic T lymphocytes (CTL) and their precursors (CTL-P) in the two major subsets of human T cells, we have used limiting dilution microculture systems to determine their frequencies. The two subsets were defined according to their reactivity (or lack thereof) with B9.4 monoclonal antibody (the specificity of which is similar, if not identical, to that of Leu 2b monoclonal antibody). Both B9+ and B9- cells obtained by sorting peripheral blood resting T cells using the fluorescence-activated cell sorter (FACS) were assayed for total CTL-P frequencies in a microculture system that allows clonal growth of every T cell. As assessed by a lectin-dependent assay, approximately 30% of peripheral blood T cells were CTP-P. In the B9+ subset (which represents 20-30% of all T cells), the CTL-P frequency was close to 100%, whereas the B9- subset had a 25-fold lower CTL-P frequency. It is thus evident that 90% and 10% of the total CTL-P in peripheral blood are confined to the B9+ or B9- T cell subsets, respectively. Analysis of the subset distribution of CTL-P directed against a given set of alloantigens confirmed these findings. CTL-P frequencies were also determined in B9+ and B9- subsets derived from T cells that had been activated in allogenic mixed leucocyte cultures (MLC). Approximately 10% of MLC T cells were CTL-P. This frequency was increased 3.5-fold in the B9+ subset, whereas the B9- subset contained only a small, although detectable number of CTL-P. Moreover, the great majority of the (operationally defined) CTL-P in MLC T cell population were found to be directed against the stimulating alloantigens, thus indicating a dramatic increase in specific CTL-P frequencies following in vitro stimulation in bulk cultures.

Antibodies, Monoclonal↗
PubMed1983

Direct demonstration of the clonogenic potential of every human peripheral blood T cell. Clonal analysis of HLA-DR expression and cytolytic activity.

In an attempt to determine the clonogenic properties of human peripheral blood T cells, we have developed a limiting dilution microculture system using phytohemagglutinin (PHA) as T cell activator and supernatant from PHA-stimulated spleen cultures as a source of T cell growth factors. The frequencies of cells capable of extensive proliferation under these culture conditions were 0.52-0.73, 0.98-1.11, and less than 0.02 in peripheral blood mononuclear, E-rosette-positive, and E-rosette-negative cell populations, respectively. The clonogenic potential of virtually all T cells was confirmed in experiments using single cells isolated by micromanipulation. Clone size ranged between 5 and 30 X 10(4) cells on day 14 of culture. The same microculture system was used to determine the precursor frequency of all cytolytic T lymphocytes (CTL-P). As assessed by a lectin-dependent 51Cr release assay, the CTL-P frequency in purified T cell populations ranged between 0.30 and 0.34. In comparison, the precursor frequency of T cells capable of lysing K562 target cells was ranging between 0.14 and 0.16. Parallel analysis of individual clonal cultures for both lytic activities showed that 50% of the clones exhibiting lectin-dependent lysis were also active against K562 target cells. All of the proliferating clones expressed HLA-DR antigens, although to a varying degree as assessed by flow cytofluorometry. Given the high cloning efficiency of this culture system, it appears now possible to determine the precursor frequencies of the various classes of functional cells in T cell populations.

Cells, Cultured↗
PubMed1982

Surface markers of cloned human T cells with helper or suppressor activity on pokeweed mitogen-driven B cell differentiation.

Human spleen T cells stimulated with pokeweed mitogen (PWM) were cloned under limiting conditions in microculture systems using interleukin 2 and irradiated autologous cells. Clones were screened for helper or suppressor activity on PWM-dependent B cell differentiation by adding cell aliquots to either isolated B cells and PWM or to mixtures of T and B cells and PWM. Out of 97 clones tested, 14 promoted intense B cell differentiation, as assessed by measurements of secreted IgG, and 6 strongly inhibited B cell maturation induced by spleen T cells. All the selected clones maintained their original activity after short-term clonal expansion; in addition, a similar (helper or suppressor) effect was detected when the total number of plasma cells per well was evaluated. Suppressor clones had no cytolytic activity on autologous T and B cell blasts, K562 cells or antibody-coated L 1210 mouse cells. Nine helper and 6 suppressor clones were analyzed for a battery of surface markers. All the clones were E rosette-positive and expressed HLA-DR (Ia) antigens. Fcmu receptor was present on a single helper clone, whereas Fc gamma receptor was expressed on a suppressor clone only. All but two clones expressed the OKT4+/ OKT8-, a single suppressor clone was OKT8+/OKT4-, whereas coexpression of OKT4 and OKT8 antigens was detected in one helper clone. Thus, the claim that helper T cells are OKT4+/OKT8- and suppressor T cells are OKT4-/OKT8+ is not supported by the analysis of their phenotype at the clonal level.

Antibodies, Monoclonal↗
PubMedDate not supplied

Recent progresses in the phenotypic and functional characterization of human cytolytic T lymphocytes.

Over the past several years, a number of major advances have been made in our understanding of the phenotypic and functional heterogeneity of human T lymphocytes. Most of these advances have resulted from: 1. the availability of monoclonal antibodies directed to T cell surface antigens; 2. the development of sensitive microassays to measure lymphocyte function in vitro; 3. the refining of T cell cloning technology. The most relevant studies in delineating how human T cell functions have been based on the analysis of T cell clones with specific cytolytic activity. These studies allowed the recent molecular definition of structures serving as specific antigen receptor on T cells as well as the understanding of the role of accessory molecules involved in specific receptor activity such as T3, T8 and T4 antigens. The development of microculture conditions allowing clonal proliferation of all human T lymphocytes, whether resting or activated, has provided a major tool for the precise definition of the frequency and subset distribution of T cells with different functional capabilities. Studies along this line have shown that precursors of cytolytic T lymphocytes (CTL-P) represent about one third of peripheral blood human T lymphocytes; in addition, all T8+ were CTL-P, whereas CTL-P were relatively rare among normal T4+ lymphocytes. As much as 20% cytolytic T lymphocytes were found to be capable to release interleukin-2 and B cell growth factor, thus indicating that cytolytic and helper function may be associated at the single cell level.

Antibodies, Monoclonal↗
PubMedDate not supplied

Therapeutic perspectives in HIV-1 infection from recent advances in HIV-1 pathogenesis: it is time to move on.

The recent availability of highly active antiretroviral combination therapy (HAART) has significantly influenced the natural history of the infection, delaying the progression to overt AIDS and prolonging survival. At the same time, the increasing knowledge on the pathogenic mechanisms an the use of HAART have challenged the most widely accepted theories about HIV-1 disease, in particular about the feasibility to eradicate the virus. This review will outline what is and what is not achievable by HAART, and will discuss new concepts in the immunopathogenesis of HIV-1 infection that provide the rationale for the design of new therapeutic approaches in the management of HIV-1 disease and AIDS.

Anti-HIV Agents↗
PubMedDate not supplied

Cyclosporin A in combination with HAART in primary HIV-1 infection.

HAART is the cornerstone of HIV therapy, and has significantly reduced morbidity and mortality associated with HIV disease. The institution of HAART during the primary HIV-1 infection has a more profound influence on the ultimate pattern and rate of disease progression than therapy commenced later on. However, it also well demonstrated that HAART alone is not able to eradicate the virus, unless over a life-long period of time. There is therefore the need to develop alternative strategies aimed at modulating the immune responses in order to achieve the long-term control of HIV even once HAART is discontinued. Among immunomodulant agents, cyclosporin A in combination with HAART might play a role in the treatment of people with primary HIV-1 infection.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Potential role of immune modulation in the effective long-term control of HIV-1 infection.

Recent advances in HIV-1 pathogenesis, and in defining virological and immunological responses to highly active antiretroviral therapy (HAART), along with the identification of the numerous drawbacks of HAART, have clearly demonstrated that the eradication of the virus is not a feasible therapeutic goal, and that there is an urgent need to develop other approaches to fight HIV-1 infection. Novel therapeutic approaches of immune modulation have recently been evaluated in pilot clinical trials. First, treating primary HIV-1 infection with cyclosporin A (CsA) coupled with HAART to target massive immune activation extends the benefits achieved with HAART during primary HIV-1 infection and might contribute to the establishment of a more favourable immunological set-point affecting the ultimate pattern and rate of disease progression. Second, treating chronic HIV-1 infection in patients with long-term suppression of virus replication induced by HAART, with the addition of mycophenolate mofetil (MMF) reduces the pool of activated CD4+ T lymphocytes able to support productive HIV-1 infection, and might have an indirect impact on the pool of resting, latently infected CD4+ T cells, contributing to its depletion in vivo. The important question is clearly whether these results will have an impact on the clinical management of patients with HIV-1 infection, determining the precise therapeutic function of drugs like CsA and MMF, thus investigating the effects of these drugs on residual viral replication and the decay of the latent reservoir, on long-term immunological benefit, and, ultimately, on clinical benefit.

Adjuvants, Immunologic↗
PubMedDate not supplied

New mechanisms of viral persistence in primary human immunodeficiency virus (HIV) infection.

Viruses, including the Human Immunodeficiency Virus (HIV), have evolved multiple strategies to overcome host immune defenses, allowing them to persist in the host. Molecular and cellular approaches were simultaneously used to provide sensitive and unbiased delineation of the diversity and dynamics of the immune response, and to study the relative compartimentalization of HIV-specific CTL clones in patients undergoing primary HIV infection. This approach revealed that some HIV-specific CTL clones can be deleted in presence of high levels of antigen, a phenomenon analogous to high-dose tolerance or clonal exhaustion described in murine models of persistent viral infections. Also, HIV-specific CTL clones were found to accumulate preferentially in peripheral blood as compared to lymph nodes, even though the large majority of viral replication during primary HIV infection takes place within lymph nodes. These two mechanisms may decrease the effectiveness of the host cell-mediated immune responses, and favor the establishment of virus persistence during primary HIV infection.

Animals↗
PubMedDate not supplied

Soluble CD30, tumour necrosis factor (TNF)-alpha, and TNF receptors in primary HIV-1 infection: relationship with HIV-1, RNA, clinical outcome and early antiviral therapy.

The natural course of human immunodeficiency type 1 (HIV-1) infection varies considerably. The identification of laboratory disease markers has become critically important to patient management. This study, carried out on 37 patients with primary HIV-1 infection (PHI), shows that, along with plasma HIV-1 RNA and CD4+ T cell counts, evaluation of plasma levels of some immune activation markers (sCD30, TNF-alpha, and sTNFR-I) may help to identify patients at risk of a more rapid disease progression, suggesting that immune activation is among the factors who determine the rate of disease progression. Early combination antiviral therapy significantly decreased levels of virus load and of immune activation markers, suggesting that it may reduce the extent of immune activation through the suppression of HIV-1 replication. Among others, sCD30 could be a more sensitive marker of immune activation, and it might be also useful in the monitoring of the response to antiviral therapy.

Anti-HIV Agents↗