HTLV type IIIB infection of human thymic epithelial cells: viral expression correlates with the induction of NF-kappa B-binding activity in cells activated by cell adhesion

Human MBP-specific T cells regulate IL-6 gene expression in astrocytes through cell-cell contacts and soluble factors

One of the distinctive features of multiple sclerosis (MS) attacks is homing to the CNS of activated T cells able to orchestrate humoral and cell-based events, resulting in immune-mediated injury to myelin and oligodendrocytes. Of the complex interplay occurring between T cells and CNS constituents, we have examined some aspects of T-cell interactions with astrocytes, the major components of the glial cells. Specifically, we focused on the ability of T cells to regulate the gene expression of interleukin-6 (IL-6) in astrocytes, based on previous evidence showing the involvement of this cytokine in CNS disorders. We found that T-cell adhesion and T-cell soluble factors induce IL-6 gene expression in U251 astrocytes through distinct signaling pathways, respectively, resulting in the activation of NF-kappaB and IRF-1 transcription factors. In a search for effector molecules at the astrocyte surface, we found that alpha3beta1 integrins play a role in NF-kappaB activation induced by T-cell contact, whereas interferon-gamma (IFN-gamma) receptors dominate in IRF-1 induction brought about by T-cell-derived soluble factors. Similar phenomena were observed also in normal fetal astrocyte cultures. We therefore propose that through astrocyte induction, T cells may indirectly regulate the availability of a cytokine which is crucial in modulating fate and behavior of cell populations involved in the pathogenesis of MS inflammatory lesions.

Contradictory Concepts in the Etiology and Regression of Kaposi's Sarcoma. The Ferenc Györkey Memorial Lecture

The Introduction is an overview of 3 decades of works performed by Professor Ferenc Györkey (in many cases in collaboration with the author) and aimed at the elucidation of viral participation in the etiology of arteriosclerosis, SLE, hairy cell leukemia, HD, AIDS and KS. Controversial issues surrounding the etiology, treatment and regression of KS are discussed in terms of paracrine and autocrine loops of growth factors; protooncogene-oncogene activations, immunosuppression and retro- and/or herpesviral etiology. In regressing KS lesions the roles played by Fas, Bcl-2, Bax, TNFß; apoptotic-antiapoptotic events; and antiangiogenesis agents especially that of Hu-r-IFNa are elaborated on.

Lymphoid adhesion promotes human thymic epithelial cell survival via NF-(kappa)B activation

Inside the thymus, thymic epithelial cells and thymocytes show an interdependent relationship for their functional differentiation and development. As regards possible interdependency for their mutual survival, it is clear that lympho-epithelial adhesion can control the survival of developing thymocytes whereas the effects of lymphoid adhesion on epithelial cell survival have never been described. To address this issue, we performed co-cultures between normal human thymic epithelial cells (TEC) and a mature lymphoid T cell line (H9) or unfractionated thymocytes. TEC were induced to apoptosis by growth factor deprivation and the level of cell death was measured by flow cytometry. TEC stimulated by cell adhesion showed a significant reduced apoptosis when compared to the control and this phenomenon was associated with increased binding activity of NF-(kappa)B, as measured by gel shift analysis. The activation of NF-(kappa)B was necessary to promote survival, since its inhibition by acetyl salicylic acid prevented the promoting effect. The mAb-mediated crosslinking of (alpha)(3)(beta)(1) was considered as a potential inducer of TEC survival, since we have previously demonstrated that the engagement of this integrin was able to induce NF-(kappa)B activation in TEC. The crosslinking of (alpha)(3)(beta)(1), which clustered at the lympho-epithelial contact sites, partially reproduced the promoting activity of cell adhesion. These results highlight that lympho-epithelial adhesion can control the survival of thymic epithelial cells through an intracellular pathway which requires the activation of NF-(kappa)B and is triggered by integrins of the (beta)(1) family.

Thymocyte Contact or Monoclonal Antibody-Mediated Clustering of 3β1 or 6β4 Integrins Activate Interleukin-6 (IL-6) Transcription Factors (NF-κB and NF-IL6) and IL-6 Production in Human Thymic Epithelial Cells

T-cell precursors develop within the thymus in contact with multiple supportive elements, among which thymic epithelial cells (TEC) are known to exert a dominant role in their homing, survival, and functional differentiation. All these functions are supported by cell-cell contacts and cytokine release. Signaling events triggered in lymphoid cells by adhesion to TEC are well characterized, but little is known about the opposite phenomenon. To address this issue, we derived cultures of TEC from human normal thymus. TEC monolayers were cocultured with thymocytes and immunostained with monoclonal antibodies (MoAbs) to integrin  (2, 3, 4, and 6) and β (β1 and β4) chains. Optical and confocal analysis showed that integrins were polarized on TEC at discrete surface locations: 6β4 lined the basal surface of TEC monolayers, whereas 3β1 was found mostly at TEC-TEC contacts; it is noteworthy that both 3β1 and 6β4 became highly enriched also at the boundaries with adherent thymocytes. Functional studies performed with MoAbs anti-β1 and -β4 integrins showed that β1, and, to a much lower extent, β4 heterodimers are involved in the TEC-thymocyte adhesion. Thymocyte contact or MoAb-mediated ligation of 3, 6, β1, and β4 integrins was investigated as a potential inducer of intracellular signaling in TEC. Thymocyte adhesion or cross-linking of MoAbs bound to integrins clustered at the TEC/thymocyte contact sites led to activation of interleukin-6 (IL-6) gene transcription factors, namely NF-IL6 serine phosphorylation and NF-κB nuclear targeting, as well as to increased IL-6 secretion. We propose that integrin clustering occurring during TEC-thymocyte contacts modulates in TEC the gene expression of a cytokine involved in thymocyte growth and functional differentiation.

Thymocyte Contact or Monoclonal Antibody-Mediated Clustering of 3β1 or 6β4 Integrins Activate Interleukin-6 (IL-6) Transcription Factors (NF-κB and NF-IL6) and IL-6 Production in Human Thymic Epithelial Cells

T-cell precursors develop within the thymus in contact with multiple supportive elements, among which thymic epithelial cells (TEC) are known to exert a dominant role in their homing, survival, and functional differentiation. All these functions are supported by cell-cell contacts and cytokine release. Signaling events triggered in lymphoid cells by adhesion to TEC are well characterized, but little is known about the opposite phenomenon. To address this issue, we derived cultures of TEC from human normal thymus. TEC monolayers were cocultured with thymocytes and immunostained with monoclonal antibodies (MoAbs) to integrin  (2, 3, 4, and 6) and β (β1 and β4) chains. Optical and confocal analysis showed that integrins were polarized on TEC at discrete surface locations: 6β4 lined the basal surface of TEC monolayers, whereas 3β1 was found mostly at TEC-TEC contacts; it is noteworthy that both 3β1 and 6β4 became highly enriched also at the boundaries with adherent thymocytes. Functional studies performed with MoAbs anti-β1 and -β4 integrins showed that β1, and, to a much lower extent, β4 heterodimers are involved in the TEC-thymocyte adhesion. Thymocyte contact or MoAb-mediated ligation of 3, 6, β1, and β4 integrins was investigated as a potential inducer of intracellular signaling in TEC. Thymocyte adhesion or cross-linking of MoAbs bound to integrins clustered at the TEC/thymocyte contact sites led to activation of interleukin-6 (IL-6) gene transcription factors, namely NF-IL6 serine phosphorylation and NF-κB nuclear targeting, as well as to increased IL-6 secretion. We propose that integrin clustering occurring during TEC-thymocyte contacts modulates in TEC the gene expression of a cytokine involved in thymocyte growth and functional differentiation.