RESUMO
INTRODUCTION: Chagas disease is a parasitic infection whose pathogenesis is related to parasite persistence and a dysfunctional cellular immune response. Variability in cytokine secretion among chronic Trypanosoma cruzi-infected patients might preclude the identification of the pool of antigen specific T cells. The goal of this study was to determine the fraction of T cells responding to T. cruzi antigen measured by the expression of membrane TNF-α and CD154. METHODS: A total of 21 chagasic patients, 11 healthy and 5 non-chagasic cardiomyopathy controls were analyzed. PBMCs were short-term cultured in the presence of anti-CD28, anti-CD49d, anti-TNF-α, and TACE (TNF-α converting enzyme) inhibitor either under T. cruzi-lysate or polyclonal stimuli. Cells were stained with anti-CD3, anti-CD4, anti-CD8, and anti-CD154, and analyzed with flow cytometry. RESULTS: CD4+ and CD8+ T cells in chagasic patients displayed higher percentages of membrane-bound TNF-α+ and CD154+ compared with controls after T. cruzi-antigen stimulation. Both markers displayed a positive correlation in the T cell subpopulations analyzed. Symptomatic chagasic patients were differentiated from asymptomatic patients based on the expression of CD154 and membrane TNF-α in TCD4+ and TCD8+ compartments, respectively. CONCLUSIONS: These results show that both markers could be useful for assessing the pool of antigen-specific T cells in chronic chagasic patients.
Assuntos
Linfócitos T CD4-Positivos/imunologia , Ligante de CD40/imunologia , Linfócitos T CD8-Positivos/imunologia , Membrana Celular/imunologia , Doença de Chagas/imunologia , Trypanosoma cruzi/imunologia , Fator de Necrose Tumoral alfa/imunologia , Adulto , Linfócitos T CD4-Positivos/metabolismo , Linfócitos T CD4-Positivos/patologia , Ligante de CD40/sangue , Linfócitos T CD8-Positivos/metabolismo , Linfócitos T CD8-Positivos/patologia , Membrana Celular/metabolismo , Doença de Chagas/sangue , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Fator de Necrose Tumoral alfa/sangueRESUMO
BACKGROUND: Chronic persistent infections have been associated with T lymphocytes functional impairment. The aim of this study was to compare the activation status, the proliferative potential and the expression of CD28 and CD3ζ chain on T lymphocytes between chronic chagasic patients and uninfected controls. METHODOLOGY/PRINCIPAL FINDINGS: Forty-two chronic chagasic patients, 28 healthy individuals and 32 non-chagasic cardiomyopathy donors were included. Peripheral blood was marked for CD3, CD4, CD8, HLA-DR, CD28, CD38 and intracellular CD3ζ. Peripheral blood mononuclear cells were stained with carboxyfluorescein diacetate succinimidylester and incubated with T. cruzi lysate or phytohemagglutinin for five days. Cells from 3 healthy controls were incubated with T. cruzi trypomastigotes separated with transwells; and the expression of CD3ζ chain and proliferation index was determined. Heart-infiltrating cells from two chronic chagasic patients were tested for the aforementioned cellular markers. Chagasic patients displayed higher frequencies of CD4+/HLA-DR+/CD38+ (8.1% ± 6.1) and CD8+/HLA-DR+/CD38+ (19.8 ± 8.9) T cells in comparison with healthy (1.6 ± 1.0; 10.6 ± 8.0) and non-chagasic cardiomyopathy donors (2.9 ± 2.9; 5.8 ± 6.8). Furthermore, the percentage of CD4+ activated T cells was higher in chagasic patients with cardiac involvement. CD8+ T cells proliferation index in chagasic donors (1.7 ± 0.3) was lower when compared with healthy (2.3 ± 0.3) and non-chagasic cardiomyopathy individuals (3.1 ± 1.1). The frequencies of CD4+/CD28+ and CD8+/CD28+ T cells, as well as the CD3ζ(bright)/CD3ζ(dim)% ratios in CD4+ and CD8+ were lower in chagasic patients when compared with both control groups. The CD3ζ(bright)/CD3ζ(dim)% ratio and proliferative indexes for CD4+ and CD8+ T lymphocytes decreased gradually in those cells cultivated with parasites and displayed lower values than those incubated with medium alone. Finally, heart-infiltrating T cells from two T. cruzi infected patients also expressed activation markers and down-regulate CD28 and CD3ζ. CONCLUSIONS: CD8+ T lymphocytes from chagasic donors displayed reduced proliferative capacity, which might be associated with CD3ζ down-regulation and diminished CD28 expression on CD4 T cells.
Assuntos
Antígenos CD28/biossíntese , Complexo CD3/biossíntese , Linfócitos T CD8-Positivos/imunologia , Doença de Chagas/imunologia , Ativação Linfocitária , Adulto , Idoso , Idoso de 80 Anos ou mais , Proliferação de Células , Regulação para Baixo , Feminino , Humanos , Imunofenotipagem , Masculino , Pessoa de Meia-IdadeRESUMO
BACKGROUND: CD4+/CD8+ double positive (DP) T cells have been described in healthy individuals as well as in patients with autoimmune and chronic infectious diseases. In chronic viral infections, this cell subset has effector memory phenotype and displays antigen specificity. No previous studies of double positive T cells in parasite infections have been carried out. METHODOLOGY/PRINCIPAL FINDINGS: Seventeen chronic chagasic patients (7 asymptomatic and 10 symptomatic) and 24 non-infected donors, including 12 healthy and 12 with non-chagasic cardiomyopathy donors were analyzed. Peripheral blood was stained for CD3, CD4, CD8, HLA-DR and CD38, and lymphocytes for intracellular perforin. Antigen specificity was assessed using HLA*A2 tetramers loaded with T. cruzi K1 or influenza virus epitopes. Surface expression of CD107 and intracellular IFN-γ production were determined in K1-specific DP T cells from 11 chagasic donors. Heart tissue from a chronic chagasic patient was stained for both CD8 and CD4 by immunochemistry. Chagasic patients showed higher frequencies of DP T cells (2.1% ± 0.9) compared with healthy (1.1% ± 0.5) and non-chagasic cardiomyopathy (1.2% ± 0.4) donors. DP T cells from Chagasic patients also expressed more HLA-DR, CD38 and perforin and had higher frequencies of T. cruzi K1-specific cells. IFN-γ production in K1-specific cells was higher in asymptomatic patients after polyclonal stimulation, while these cells tended to degranulate more in symptomatic donors. Immunochemistry revealed that double positive T cells infiltrate the cardiac tissue of a chagasic donor. CONCLUSIONS: Chagasic patients have higher percentages of circulating double positive T cells expressing activation markers, potential effector molecules and greater class I antigenic specificity against T. cruzi. Although K1 tetramer positive DP T cell produced little IFN-γ, they displayed degranulation activity that was increased in symptomatic patients. Moreover, K1-specific DP T cells can migrate to the heart tissue.