Umbilical-Cord-Derived Mesenchymal Stromal Cells Modulate 26 Out of 41 T Cell Subsets from Systemic Sclerosis Patients

Systemic sclerosis (SSc) is an immune-mediated disease wherein T cells are particularly implicated, presenting a poor prognosis and limited therapeutic options. Thus, mesenchymal-stem/stromal-cell (MSC)-based therapies can be of great benefit to SSc patients given their immunomodulatory, anti-fibrotic, and pro-angiogenic potential, which is associated with low toxicity. In this study, peripheral blood mononuclear cells from healthy individuals (HC, n = 6) and SSc patients (n = 9) were co-cultured with MSCs in order to assess how MSCs affected the activation and polarization of 58 different T cell subsets, including Th1, Th17, and Treg. It was found that MSCs downregulated the activation of 26 out of the 41 T cell subsets identified within CD4⁺, CD8⁺, CD4⁺CD8⁺, CD4^-CD8^-, and γδ T cells in SSc patients (HC: 29/42) and affected the polarization of 13 out of 58 T cell subsets in SSc patients (HC: 22/64). Interestingly, SSc patients displayed some T cell subsets with an increased activation status and MSCs were able to downregulate all of them. This study provides a wide-ranging perspective of how MSCs affect T cells, including minor subsets. The ability to inhibit the activation and modulate the polarization of several T cell subsets, including those implicated in SSc's pathogenesis, further supports the potential of MSC-based therapies to regulate T cells in a disease whose onset/development may be due to immune system's malfunction.

The multigenic structure of the MHC locus contributes to positive selection efficiency: a role for MHC class II gene-specific restriction

The study of T cell positive selection in the thymus has long been focused on the specificity of the MHC-TCR interactions, making use of genetically manipulated mice that display TCR specificities or selecting peptides of limited diversity. However, little is known on the role of the MHC molecules irrespective of the peptide specificity and the implications of MHC multigenic structure in thymic positive selection have not been addressed. Here, we investigated the effect of MHC class II genetic configuration on the positive selection efficiency of naturally generated pre-selection repertoires in the mouse thymus. Analysis of positively selected thymocyte populations in MHC-congenic and -transgenic mice revealed that expression of I-E molecule in the thymic cortex increases positive selection efficiency of CD4 cells by approximately 50%. We show that increments in positive selection attributable to either the I-A and I-E genes are not due to increased MHC class II expression in the thymic cortex and are not affected by the number of MHC alleles. Collectively, our findings imply that MHC class II gene-restricted TCR specificities significantly contribute to positive selection efficiency, introducing the notion that multigenic structure of the MHC locus serves to increase selection of non-overlapping TCR repertoires.

First isolation of Borrelia lusitaniae from a human patient

The first human isolate of Borrelia lusitaniae recovered from a Portuguese patient with suspected Lyme borreliosis is described. This isolate, from a chronic skin lesion, is also the first human isolate of Borrelia in Portugal. Different phenotypic and molecular methods are used to characterize it.