Hypereosinophilia with abnormal T cells, trisomy 7 and elevated TARC serum level.

The idiopathic hypereosinophilic syndrome (HES) is a rare heterogeneous disorder, characterized by persistent blood eosinophilia with possible organ involvement. We describe here the case of a 20-year-old atopic male presenting chronic hypereosinophilia and eczema since childhood. Biological findings included hypereosinophilia (9.5 x 10(9)/L), hyperlymphocytosis (10.9 x 10(9)/L), polyclonal hypergammaglobulinemia and elevated IgE serum level. Flow cytometric analysis of blood lymphoid cells showed a population of CD2+CD3-CD4+TCRab-TCRgd- lymphocytes. These cells displayed a Th0/Th2 cytokine profile, and a clonal TCR rearrangement pattern. A high serum TARC level was observed. Karyotype studies on blood stimulated culture or lymph nodes revealed a cellular hyperdiploïd clone 47, XY, +7. To our knowledge, this chromosomal aberration has never been reported in such case.

Cultured Kaposi's sarcoma tumor cells exhibit a chemokine receptor repertoire that does not allow infection by HIV-1.

BACKGROUND: HIV-1 is known to play a critical role in the pathogenesis of AIDS-associated Kaposi's sarcoma (KS). However, it remains controversial whether KS cells are target cells for HIV infection. The aim of this study was to investigate the expression of chemokine receptors in KS cell cultures and to determine whether these cells can be infected by HIV-1. MATERIAL AND METHODS: KS-derived cells and KS-Y1 cells were investigated using RT-PCR for the expression of CD4, CCR3, CCR5, CCR8 and CXCR4 mRNA. HIV infectivity of these cells was determined by p24 antigen and HIV-1 RNA production, as well as by HIV-1 DNA integration. RESULTS AND DISCUSSION: With the exception of CCR8 which is expressed by KS-derived spindle cell cultures but not by KS-Y1 cells, unstimulated KS cells express no significant levels of CD4, CCR3, CCR5 or CXCR4 mRNA. HIV infectivity assays showed that KS cells were unpermissive to HTLVIIIB and JRFL strains. Although the expression of CXCR4 mRNA could be upregulated by interleukin-1beta, stimulation of KS cells by this cytokine did not allow infection by HIV-1. CONCLUSIONS: This shows that KS cells exhibit a chemokine receptor repertoire that does not allow infection by HIV-1. Other cell types making up KS lesions, such as inflammatory cells, are likely to represent the source of HIV-1 products cooperating to promote KS development and progression.

Clonal Th2 cells associated with chronic hypereosinophilia: TARC-induced CCR4 down-regulation in vivo.

We analyzed the expression of chemokine receptors on clonal Th2-type CD4(+)CD3(- )lymphocytes isolated from blood of two patients with chronic hypereosinophilia. First, we observed that these Th2 cells express membrane CCR5 and CXCR4 but neither CCR3 nor CCR4 when analyzed immediately after purification. However, CCR4 appeared following culture in human serum-free medium, suggesting that it was down-regulated in vivo. Indeed, patient's serum, but not control human serum, strongly down-regulated CCR4 expression on cultured Th2 cells. As high levels of TARC, a CCR4 ligand, were detected in the serum of four hypereosinophilic patients with CD3(-)CD4(+) clonal Th2 cells, we evaluated the effect of TARC neutralization in this system. Addition of a neutralizing anti-TARC mAb inhibited CCR4 down-regulation by patient's serum, indicating that circulating TARC contributed to CCR4 down-regulation on Th2 cells in vivo. Clonal Th2 cells did not secrete high levels of TARC themselves but induced a sustained production of TARC by monocyte-derived dendritic cells, a phenomenon that was inhibited by addition of blocking mAb against IL-4 receptor. We conclude that high circulating levels of TARC in serum of patients with chronic hypereosinophilia, most likely derived from antigen-presenting cells stimulated by Th2-type cytokines, induce down-regulation of CCR4 on Th2 cells in vivo.

Interferon alpha prevents spontaneous apoptosis of clonal Th2 cells associated with chronic hypereosinophilia.

A recent study identified a clonal expansion of CD3(-)CD4(+)cells secreting Th2-type cytokines in 4 patients with chronic hypereosinophilia. Because interferon alpha (IFN-alpha) is used in the therapy of the idiopathic hypereosinophilic syndrome, the effects of this cytokine on the survival of clonal Th2 cells isolated from the blood of 2 patients were determined. First, these cells displayed a high rate of spontaneous apoptosis on culture in cytokine-free medium and were also sensitive to Fas-mediated apoptosis induced by soluble Fas ligand. Addition of IFN-alpha or interleukin-2 (IL-2) to culture medium resulted in significant protection against spontaneous but not Fas-induced apoptosis. Although spontaneous apoptosis of the clonal Th2 cells was clearly associated with down-regulation of both bcl-2 and bcl-x(L) levels, IFN-alpha had no significant effect on the expression of these antiapoptotic proteins, whereas addition of IL-2 resulted in higher levels of bcl-2. On the other hand, IFN-alpha decreased the numbers of cells with disrupted mitochondrial transmembrane potential both during spontaneous apoptosis and after exposure to protoporphyrin IX. Thus, IFN-alpha might promote the survival of clonal Th2 cells, an effect that could be relevant to the therapeutic approach for patients with chronic hypereosinophilia caused by clonal expansion of Th2-type cells. (Blood. 2000;96:4285-4292)

CD40 engagement on endothelial cells promotes tissue factor-dependent procoagulant activity.

The CD40 molecule expressed on endothelial cells has been shown to transduce activation signals resulting in upregulation of adhesion molecules. Herein, we studied the impact of CD40 engagement on the induction of tissue factor (TF)-dependent procoagulant activity (PCA) at the surface of human umbilical vein endothelial cells (HUVECs). First, we found that co-incubation of HUVECs with 3T6 fibroblasts transfected with the CD40L gene (3T6-CD40L) resulted in a clear induction of PCA which was not observed with control untransfected fibroblasts. The specificity of this finding was established by inhibition experiments using monoclonal antibodies (mAbs) blocking CD40 or CD40L. PCA induced by CD40 ligation was TF-related as it was not observed in factor VII-deficient plasma and was associated with the accumulation of TF mRNA. To investigate the role of CD40/CD40L interactions in the induction of endothelial cell PCA by lymphocytes, interferon (IFN)-gamma-stimulated EC were incubated with T cells in the absence or presence of anti-CD40 or anti-CD40L mAb. The 60-70% inhibition of PCA induced by these mAbs but not their isotype-matched control indicated that the CD40 pathway is involved in the induction of PCA resulting from interactions between activated HUVECs and T cells. We conclude that activation signals elicited by CD40 engagement on endothelial cells result in the induction of TF-dependent PCA. The CD40/CD40L pathway might therefore be involved in the development of prothrombic states during diseases associated with endothelial cell and T cell activation.