Analysis of the peripheral T-cell compartment in the MHC class II deficiency syndrome.

To analyse the impact of lack of MHC class II expression on the composition of the peripheral T-cell compartment in man, the expression characteristics of several membrane antigens were examined on peripheral blood lymphocytes (PBL) and cultured T cells derived from an MHC-class-II-deficient patient. No MHC class II expression could be detected on either PBL or activated T cells. Moreover, the expression of MHC class I was reduced both on PBL and in vitro activated T cells compared to the healthy control. However, the reduced expression of CD26 observed on the PBL of the patient was restored after in vitro expansion. Despite the presumably class-II-deficient thymic environment, a distinct but reduced single CD4+ T-cell population was observed in the PBL of the patient. After in vitro expansion, the percentage of CD4+ cells dropped even further, most likely due to a proliferative disadvantage, compared to the single CD8+ T-cell population. However, proliferation analysis showed that T-cell activation via the TcR/CD3 pathway is not affected by the MHC class II deficiency.

Age-related immune reconstitution during highly active antiretroviral therapy in human immunodeficiency virus type 1-infected children.

OBJECTIVES: To evaluate the immune reconstitution in HIV-1-infected children in whom highly active antiretroviral therapy (HAART) controlled viral replication and to assess the existence of a relation between the magnitude of this restoration and age. METHODS: All HIV-1-infected children in whom a new HAART decreased plasma viral load below 400 copies/ml after 3 months of therapy were prospectively enrolled in a study of their immune reconstitution. Viral load, lymphocyte phenotyping, determination of CD4+ and CD8+ T cell receptor repertoires and proliferative responses to mitogens and recall antigens were assessed every 3 months during 1 year. RESULTS: Nineteen children were evaluated. Naive and memory CD4+ percentages were already significantly increased after 3 months of HAART. In contrast to memory CD4+ percentages, naive CD4+ percentages continued to rise until 12 months. Age at baseline was inversely correlated with the magnitude of the rise in naive CD4+ cells after 3, 6 and 9 months of therapy but not after 12 months. Although memory and activated CD8+ cells were already decreasing after 3 months, abnormalities of the CD8 T cell receptor repertoire and activation of CD8+ cells persisted at 1 year. HAART increased the response to mitogens as early as 3 months after starting therapy. CONCLUSIONS: In children the recovery of naive CD4+ cells occurs more rapidly if treatment is started at a younger age, but after 1 year of viral replication control, patients of all ages have achieved the same level of restoration. Markers of chronic activation in CD8+ cells persist after 1 year of HAART.

Cellular immune responses in human immunodeficiency virus (HIV)-1-infected children: Is immune restoration by highly active anti-retroviral therapy comparable to non-progression?

The objective of this study was to investigate whether the restored immune functions of vertically human immunodeficiency virus (HIV)-infected children who were severely immunodeficient before the initiation of highly active anti-retroviral therapy (HAART) are comparable to those of untreated slow progressors. We therefore assessed T cell proliferation and cytokine [interferon (IFN)-γ, interleukin (IL)-5 and IL-13] secretions after mitogen, recall antigens and HIV-1-specific stimulation in 12 untreated slow progressors, 16 untreated progressors and 18 treated patients. Treated children were profoundly immunodeficient before the initiation of HAART and had long-lasting suppression of viral replication on treatment. We demonstrated that slow progressors are characterized not only by the preservation of HIV-1-specific lymphoproliferative responses but also by the fact that these responses are clearly T helper type 1 (Th1)-polarized. Children on HAART had proliferative responses to HIV-1 p24 antigen, purified protein derivative (PPD) and tetanus antigen similar to slow progressors and higher than those of progressors. However, in contrast to slow progressors, most treated children exhibited a release of Th2 cytokines accompanying the IFN-γ secretion in response to the HIV-1 p24 antigen. Moreover, despite higher proliferative responses to phytohaemagglutinin (PHA) than the two groups of untreated children, treated children had lower levels of IFN-γ secretion in response to PHA than slow progressors. These data show that in severely immunodeficient vertically HIV-infected children, a long-lasting HAART allows recovering lymphoproliferative responses similar to untreated slow progressors. However, alterations in IFN-γ secretion in response to the mitogen PHA persisted, and their cytokine release after HIV-specific stimulation was biased towards a Th2 response. © 2011 The Authors. Clinical and Experimental Immunology © 2011 British Society for Immunology.

Characterization of autonomous thyroid adenoma: metabolism, gene expression, and pathology.

Fifty-one in vivo characterized autonomous single adenomas have been studied for functional parameters in vitro, for gene and protein expression and for pathology, and have been systematically compared to the corresponding extratumoral quiescent tissue. The adenomas were characterized by a high level of iodide trapping that corresponds to a high level of Na+ /iodide symporter gene expression, a high thyroperoxidase mRNA and protein content, and a low H2O2 generation. This explains the iodide metabolism characteristics demonstrated before, ie, the main cause of the "hot" character of the adenomas is their increased iodide transport. The adenomas spontaneously secreted higher amounts of thyroid hormone than the quiescent tissue and in agreement with previous in vivo data, this secretion could be further enhanced by thyrotropin (TSH). Inositol uptake was also increased but there was no spontaneous increase of the generation of inositol phosphates and this metabolism could be further activated by TSH. These positive responses to TSH are in agreement with the properties of TSH-stimulated thyroid cells in vitro and in vivo. They are compatible with the characteristics of mutated TSH receptors whose constitutive activation accounts for the majority of autonomous thyroid adenomas in Europe. The number of cycling cells, as evaluated by MIB-1 immunolabeling was low but increased in comparison with the corresponding quiescent tissue or normal tissue. The cycling cells are observed mainly at the periphery; there was very little apoptosis. Both findings account for the slow growth of these established adenomas. On the other hand, by thyroperoxidase immunohistochemistry, the whole lesion appeared hyperfunctional, which demonstrates a dissociation of mitogenic and functional stimulations. Thyroglobulin, TSH receptor, and E-cadherin mRNA accumulations were not modified in a consistent way, which confirms the near-constitutive expression of the corresponding genes in normal differentiated tissue. On the contrary, early immediate genes expressions (c-myc, NGF1B, egr 1, genes of the fos and jun families) were decreased. This may be explained by the proliferative heterogeneity of the lesion and the previously described short, biphasic expression of these genes when induced by mitogenic agents. All the characteristics of the autonomous adenomas can therefore be explained by the effect of the known activating mutations of genes coding for proteins of the TSH cyclic adenosine monophosphate (cAMP) cascade, all cells being functionally activated while only those at the periphery multiply. The reason of this heterogeneity is unknown.

Study of gene expression in thyrotropin-stimulated thyroid cells by cDNA expression array: ID3 transcription modulating factor as an early response protein and tumor marker in thyroid carcinomas.

Induction of cell proliferation by mitogen or growth factor stimulation leads to the specific induction or repression of a large number of genes. To identify genes differentially regulated by the cAMP-dependent transduction pathway, which is poorly characterized so far, we used the cDNA expression array technology. Hybridizations of Atlas human cDNA expression arrays with (32)P-labeled cDNA probes derived from control or thyrotropin (TSH)-stimulated dog thyrocytes in primary culture generated expression profiles of hundreds of genes simultaneously. Among the genes that displayed modified expression, we selected the transcription factor ID3, whose expression was increased by a cAMP-dependent stimulus. ID3 overexpression after TSH stimulation was first verified by Northern blotting analysis, and its mRNA regulation was then investigated in response to a variety of agents acting on thyrocyte proliferation and/or differentiation. We show that: (1) ID3 mRNA induction was stronger after stimulation of the cAMP cascade, but was not restricted to this signaling pathway, as phorbol myristate ester (TPA) and insulin also stimulated mRNA accumulation; (2) in contrast, powerful mitogens for thyroid cells, epidermal growth factor and hepatocyte growth factor, did not significantly modify ID3 mRNA levels; (3) ID3 protein levels closely parallelled mRNA levels, as revealed by immunofluorescence experiments showing a nuclear signal regulated by TSH; (4) in papillary thyroid carcinomas, ID3 mRNA was downregulated. Our results suggest that ID3 expression might be more related to the differentiating process induced by TSH than to the proliferative action of this hormone.