Abstract
BackgroundPrevious data have suggested that regulatory T cells (Tregs) balance protective immune responses with immune mediated pathology in malaria. This study aimed to determine to test the hypothesis that Treg proportions or absolute levels are associated with parasitaemia and malaria symptoms.MethodsTreg cells were quantified by flow cytometry as CD4+ CD25+, Foxp3+, CD127low T cells. Three patient groups were assessed: patients with symptomatic Plasmodium falciparum malaria (S), subjects with asymptomatic P. falciparum parasitaemia (AS) and uninfected control individuals (C).ResultsS, AS and C groups had similar absolute numbers and percentage of Tregs (3.9%, 3.5% and 3.5% respectively). Levels of parasitaemia were not associated with Treg percentage (p = 0.47).ConclusionNeither relative nor absolute regulatory T cell numbers were found to be associated with malaria-related symptomatology in this study. Immune mechanisms other than Tregs are likely to be responsible for the state of asymptomatic P. falciparum parasitaemia in the Peruvian Amazon; but further study to explore these mechanisms is needed.
Highlights
Previous data have suggested that regulatory T cells (Tregs) balance protective immune responses with immune mediated pathology in malaria
Elevated levels of circulating tumor necrosis factor (TNF), interleukin-6 (IL-6), IL-12, IL-1β, and IL-10 have been reported to correlate with malaria disease severity and with fatal outcomes [7,8]; the behaviour of these cytokines in asymptomatic parasitaemia remains unknown
There were no significant differences in Treg cell percentage among patients with uncomplicated P. falciparum malaria S, asymptomatic P. falciparum parasitaemia (AS), and C individuals [H = 0.613, df = 2, p = 0.736] (Figure 1), or absolute Treg cell numbers between S and AS patients (Table 1), according to the Kruskal-Wallis test
Summary
Previous data have suggested that regulatory T cells (Tregs) balance protective immune responses with immune mediated pathology in malaria. The concept of asymptomatic parasitaemia and its potential interaction with the human immune system to malaria infection has emerged on the forefront of why some individuals are able to control the infection with lack of symptoms [3,4,5,6]. This concept implies that individuals with low parasitaemia, in the absence of clinical symptoms (i.e. fever, headache, chills, malaise, etc.). Interest has recently arisen in mechanisms of immune regulation mediated by CD4+, CD25+, FoxP3+ regulatory T cells (Tregs) This T-cell subset has been shown to play an important role in maintaining immune homeostasis and controlling excessive immune responses [7]. These cells have been reported to suppress cellular immune responses through direct contact with immune effectors cells and by production of regulatory cytokines, including TGF-ß and IL-10 [7]
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