Boeuf, Philippe S4; Loizon, Séverine4; Awandare, Gordon A4; Tetteh, John Ka4; Addae, Michael M4; Adjei, George O4; Goka, Bamenla4; Kurtzhals, Jørgen Al6; Puijalon, Odile4; Hviid, Lars7; Akanmori, Bartholomew D4; Behr, Charlotte4
1 Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, Københavns Universitet2 Centre for Medical Parasitology, Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, Københavns Universitet3 Department of Clinical Medicine, Faculty of Health and Medical Sciences, Københavns Universitet4 unknown5 Department of Immunology and Microbiology, Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, Københavns Universitet6 Department of Immunology and Microbiology, Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, Københavns Universitet7 Centre for Medical Parasitology, Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, Københavns Universitet
implications for understanding severe malarial anaemia
ABSTRACT: BACKGROUND: Severe malarial anaemia (SMA) is a major life-threatening complication of paediatric malaria. Protracted production of pro-inflammatory cytokines promoting erythrophagocytosis and depressing erythropoiesis is thought to play an important role in SMA, which is characterized by a high TNF/IL-10 ratio. Whether this TNF/IL-10 imbalance results from an intrinsic incapacity of SMA patients to produce IL-10 or from an IL-10 unresponsiveness to infection is unknown. Monocytes and T cells are recognized as the main sources of TNF and IL-10 in vivo, but little is known about the activation status of those cells in SMA patients. METHODS: The IL-10 and TNF production capacity and the activation phenotype of monocytes and T cells were compared in samples collected from 332 Ghanaian children with non-overlapping SMA (n = 108), cerebral malaria (CM) (n = 144) or uncomplicated malaria (UM) (n = 80) syndromes. Activation status of monocytes and T cells was ascertained by measuring HLADR + and/or CD69+ surface expression by flow cytometry. The TNF and IL-10 production was assessed in a whole-blood assay after or not stimulation with lipopolysaccharide (LPS) or phytohaemaglutinin (PHA) used as surrogate of unspecific monocyte and T cell stimulant. The number of circulating pigmented monocytes was also determined. RESULTS: Monocytes and T cells from SMA and CM patients showed similar activation profiles with a comparable decreased HLA-DR expression on monocytes and increased frequency of CD69+ and HLA-DR + T cells. In contrast, the acute-phase IL-10 production was markedly decreased in SMA compared to CM (P = .003) and UM (P = .004). Although in SMA the IL- 10 response to LPS-stimulation was larger in amplitude than in CM (P = .0082), the absolute levels of IL-10 reached were lower (P = .013). Both the amplitude and levels of TNF produced in response to LPS-stimulation were larger in SMA than CM (P = .019). In response to PHA-stimulation, absolute levels of IL-10 produced in SMA were lower than in CM (P = .005) contrasting with TNF levels, which were higher (P = .01). CONCLUSIONS: These data reveal that SMA patients have the potential to mount efficient IL-10 responses and that the TNF/IL-10 imbalance may reflect a specific monocyte and T cell programming/polarization pattern in response to infection.