Alterations in immune cell subsets and their cytokine secretion profile in childhood idiopathic thrombocytopenic purpura (ITP)

Abstract

Immune thrombocytopenic purpura (ITP) is acquired autoimmune disease in children characterized by the breakdown of immune tolerance. This work is designed to explore the contribution of different lymphocyte subsets in acute and chronic ITP children. Imbalance in the T helper type 1 (Th1)/Th2 cytokine secretion profile was investigated. The frequency of T (CD3(+), CD4(+), CD8(+)) and B (CD19(+)) lymphocytes, natural killer (NK) (CD16(+) 56(+)) and regulatory T (T(reg)) [CD4(+) CD25(+high) forkhead box protein 3 (FoxP3)(+) ] cells was investigated by flow cytometry in 35 ITP children (15 acute and 20 chronic) and 10 healthy controls. Plasma levels of Th1 cytokines [interferon (IFN-γ) and tumour necrosis factor (TNF-α)] and Th2 [interleukin (IL)-4, IL-6 and IL-10)] cytokines were measured using enzyme-linked immunosorbent assay (ELISA). The percentage of Treg (P < 0·001) and natural killer (NK) (P < 0·001) cells were significantly decreased in ITP patients compared to healthy controls. A negative correlation was reported between the percentage of T(reg) cells and development of acute (r = -0·737; P < 0·01) and chronic (r = -0·515; P < 0·01) disease. All evaluated cytokines (IFN-γ, TNF-α, IL-4, IL-6 and IL-10) were elevated significantly in ITP patients (P < 0·001, P < 0·05, P < 0·05, P < 0·05 and P < 0·001, respectively) compared to controls. In conclusion, our data shed some light on the fundamental role of immune cells and their related cytokines in ITP patients. The loss of tolerance in ITP may contribute to the dysfunction of T(regs). Understanding the role of T cell subsets will permit a better control of autoimmunity through manipulation of their cytokine network.

Keywords: ITP; NK cells; Th1 and Th2 cells; Treg.

Figure 1

Flow cytometric detection of T lymphocytes, B lymphocytes, natural killer (NK) cells and CD4⁺CD25^+highforkhead box protein 3 (FoxP3)⁺ regulatory T cells. Forward- and side-scatter histograms were used define the lymphocyte population. A1, A2 and A3: the expression of CD4⁺and CD8⁺ was assessed in the total lymphocyte population. B1, B2 and B3: the expression of CD3⁺ and CD19⁺ was assessed in total lymphocytes population. C1, C2 and C3: the expression of CD3⁺ and CD16⁺56⁺ was assessed in the total lymphocyte population. D1, D2 and D3: the expression of TCR-γδ was assessed in the total lymphocyte population. E1, E2 and E3: the expression of CD4⁺ and CD25⁺ in total lymphocytes was detected and different gates were performed to define CD4⁺CD25^+high cells; F1, F2 and F3 show the percentage of CD4⁺CD25^+highFoxP3.

Figure 2

Plasma levels of T helper type 1 (Th1) [interferon (IFN-γ) and tumour necrosis factor (TNF-α)] and Th2 [interleukin (IL)-4, IL-6 and IL-10] cytokines. Results are expressed as mean ± standard error. (a) Groups statistically significantly different from controls. (b) Groups statistically significantly different from acute immune thrombocytopenia purpura (ITP) patients.*P < 0·05; **P < 0·01; ***P < 0·001.