T Lymphocytes from Chagasic Patients Are Activated but Lack Proliferative Capacity and Down-Regulate CD28 and CD3ζ

Nicolás A Giraldo,Adriana Cuellar,Nubia Roa,John M González,Zulma Cucunubá,Fernando Rosas,Natalia I Bolaños,Víctor Velasco,Concepción J Puerta,Mauricio Martins Rodrigues

doi:10.1371/journal.pntd.0002038

Abstract

BackgroundChronic 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 FindingsForty-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 CD3ζbright/CD3ζdim% ratios in CD4+ and CD8+ were lower in chagasic patients when compared with both control groups. The CD3ζbright/CD3ζdim% 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.ConclusionsCD8+ 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.

Highlights

Upon first contact with an infectious agent, antigen-specific T cells proliferate and rapidly expand their number in order to control or eliminate the microorganism [1]
CD8+ T lymphocytes from chagasic donors displayed reduced proliferative capacity, which might be associated with CD3f down-regulation and diminished CD28 expression on CD4 T cells
Chagasic patients displayed higher frequencies of T lymphocytes co-expressing CD38 and HLA-DR, and the percentage of activated CD4+ T cells is correlated with the disease stage

Summary

Introduction

Upon first contact with an infectious agent, antigen-specific T cells proliferate and rapidly expand their number in order to control or eliminate the microorganism [1]. In some chronic infections, activated CD38+/HLADR+ T cells can be persistently expanded [6,7] and to some extent correlate with disease progression [8,9]. With this phenomenon, numerous cellular effector functions including cytokine production, cytotoxic potential and proliferative capacity becomes impaired, in a process termed lymphocyte exhaustion [10,11]. The aim of this study was to compare the activation status, the proliferative potential and the expression of CD28 and CD3f chain on T lymphocytes between chronic chagasic patients and uninfected controls

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Discussion

Conclusion