CD19-deficient mice were generated to examine the role of CD19 in B cell growth regulation in vivo. Deletion of CD19 had no deleterious effects on the generation of B cells in the bone marrow, but there was a significant reduction in the number of B cells in peripheral lymphoid tissues. B cells from CD19-deficient mice exhibited markedly decreased proliferative responses to mitogens, and serum immunoglobulin levels were also significantly decreased. In contrast, mice that overexpressed CD19 had significant defects in early B cell development in the bone marrow, augmented mitogenic responses, and increased serum immunoglobulin levels. These experiments indicate that CD19 functions to define signaling thresholds for cell surface receptors that regulate B lymphocyte selection, activation, and differentiation.

SummaryFollowing occupancy of the T cell receptor by antigen, T cell proliferation and lymphokine production are determined by a second costimulatory signal delivered by a ligand expressed on antigen presenting cells. The human B cell activation antigen B7, which is expressed on antigen presenting cells including activated B cells and 'Y interferon treated monorytes, has been shown to deliver such a costimulatory signal upon attachment to its ligand on T cells, CD28. We have cloned and sequenced the murine homologue of the human B7 gene . The predicted murine protein has 44% amino acid identity with human B7 . The greatest similarity is in the IgV and Ig-C like domains . Murine B7 mRNA was detected in murine hematopoietic cells of B cell but not T cell origin . Cells transfected with murine B7 provided a costimulatory signal to human CD28+ T lymphocytes. These results demonstrate the costimulatory activity of murine B7 and provide evidence that the ligand attachment site is conserved between the two species .Although occupancy of the TCR complex by antigen in 13, association with the MHC is necessary for the initiation of T cell activation, several lines of evidence suggest that a second costimulatory signal is essential for the induction of proliferation and lymphokine secretion (1-4) . In murine and human systems, this costimulatory signal is delivered by APC and requires cell to cell contact (2, 4) . Cells which can deliver this costimulatory signal include activated, but not resting B lymphocytes (5), INF-y activated monorytes, and dendritic cells (2, 6) .Several recent studies in human systems have provided compelling evidence that the B cell activation antigen B7 can provide one such costimulatory signal (7-9) . B7, a member of the Ig supergene family, has been shown to be a ligand for another member of this family, the T cell surface protein CD28, (10-13) . CD28 is constitutively expressed on 95% of human CD4+ T cells, 50% of CD8+ T cells, and on thymocytes which coexpress CD4 and CD8 (14-16) . Following suboptimal activation of T cells with anti-CD3 mAb (16), anti-CD2 mAb, or phorbol ester (17), crosslinking of CD28 by anti-CD28 mAb results in enhanced T cell proliferation and greatly augments synthesis of multiple lymphokines (18). B7 is likely to be an important regulator of T cell proliferation and lymphokine production as evidenced by its pattern of expression and functional activity. B7 is not expressed on resting B cells (19) but appears following crosslinking of surface Ig (10, 19) or class II MHC (9) . Moreover, B7 is not expressed on unstimulated monorytes and is specifically induced by INF-y but not other stimuli which activate monocytes (20). Human B7 (hB7) 1 transfected cells or recombinant B7-Ig fusion protein augment proliferation and induce IL2, but not IIT4, synthesis in T cells which have been treated with phorbol ester or anti-CD3 mAb (7-9) .In murine systems, a homologue for CD28 has recently been cloned (21); however, a conserved functional activity has not yet been demonstrated . In ...

CD19 is a B-cell-specific member of the immunoglobulin superfamily expressed from early pre-B-cell development until plasma cell differentiation. In vitro studies demonstrate that the CD19 signal transduction molecule can serve as a costimulatory molecule for activation through other B-lymphocyte cell surface molecules. However, much remains to be known regarding how CD19 functions in vivo and whether CD19 has different roles at particular stages of B-cell differentiation. Therefore, transgenic mice overexpressing the human CD19 (hCD19) gene were generated to determine whether this transgene would be expressed in a B-lineage-specific fashion and to dissect the in vivo role of CD19 in B-cell development and activation. Expression of the human transgene product was specifically restricted to all B-lineage cells and appeared early in development as occurs with hCD19. In addition, expression of hCD19 severely impaired the development of immature B cells in the bone marrow, with dramatically fewer B cells found in the spleen, peripheral circulation, and peritoneal cavity. CD19 (48,50), and the cytoplasmic domain of CD19 contains kinase insert regions that when phosphorylated mediate the binding and activation of phosphatidylinositol 3-kinase (47). Thus, although the precise in vivo function of CD19 has not been definitively elucidated, these studies support the hypothesis that the CD19 complex can serve an accessory role in conjunction with surface Ig to enhance antigen-driven B-cell activation (6).Although CD19 is one of the first lineage-specific surface molecules expressed during early pre-B-cell development, little is known about the functional importance of this molecule during early B-cell differentiation or the role of CD19 in vivo. However, the expression of cloned genes in transgenic mice can provide a direct readout of biological consequences of receptor function rather than the effects evoked following cross-linking of a receptor with MAb as has primarily been the approach for examining CD19 function. Further, the mouse model allows an analysis of the complex signaling pathways that occur during early B-cell hematopoiesis for which satisfactory tissue culture models do not exist. Therefore, the human CD19 (hCD19) gene was microinjected into mouse 3884 on April 4, 2019 by guest

Background:The immunosuppressive activity of mesenchymal stem cells (MSCs) has been exploited to induce tolerance after organ transplantation. The indoleamine 2,3-dioxygenase (IDO) may have beneficial effects in the immunoregulatory properties of MSCs. It was recently revealed that exosomes derived from MSCs play important roles in mediating the biological functions of MSCs. This study aimed to explore the roles of exosomes derived from MSCs in the induction of immune tolerance.Methods:Dendritic cells (DCs) and T-cells were cultured with exosomes derived from rat bone marrow MSCs (BMSCs) overexpressing IDO1 or controls. For the in-vivo study, rats received heart transplants and were treated with exosomes from IDO-BMSCs and heart function was evaluated. Flow cytometry was used to detect expression of cell surface markers. Cytokine levels were detected in culture supernatants or serum samples. Protein and microRNA expressions in exosomes were investigated by chips.Results:Exosomes from IDO-BMSCs cultured with DCs and T-cells (1) downregulated CD40, CD86, CD80, MHC-II, CD45RA, CD45RA+CD45RB, OX62, and upregulated CD274 expression, (2) increased the number of regulatory T-cells (Tregs) and decreased the number of CD8+ T-cells, and (3) decreased the levels of pro-inflammatory cytokines, but increased the levels of anti-inflammatory cytokines compared with the other groups. Transplanted rats, which were injected with exosomes from IDO-BMSCs, had reduced allograft-targeting immune responses and improved cardiac allograft function. Exosomes secreted by IDO-BMSCs exhibited significant upregulations of the immunoregulatory protein FHL-1, miR-540-3p, and a downregulation of miR-338-5p.Conclusion:Exosomes derived from IDO-BMSCs can be used to promote immunotolerance and prolong the survival of cardiac allografts.

In clinical studies, OM-85 Broncho-Vaxom®, a bacterial lysate, reduced viral respiratory tract infection. Infection of epithelial cells by SARS-CoV-2 depends on the interaction of its spike-protein (S-protein) with host cell membrane proteins. In this study, we investigated the effect of OM-85 on the expression of S-protein binding proteins by human bronchial epithelial cells. Human bronchial epithelial cells were treated with OM-85 over 5 days. The expression of SARS-CoV-2 receptor angiotensin converting enzyme 2 (ACE2), transmembrane protease serine subtype 2 (TMPRSS2), dipeptidyl peptidase-4 (DPP4), and a disintegrin and metalloprotease 17 (ADAM17) were determined by Western blotting and quantitative RT-PCR. Soluble (s)ACE2, heparan sulfate, heparanase, and hyaluronic acid were assessed by ELISA. OM-85 significantly reduced the expression of ACE2 (p < 0.001), TMPRSS2 (p < 0.001), DPP4 (p < 0.005), and cellular heparan sulfate (p < 0.01), while ADAM17 (p < 0.02) expression was significantly upregulated. Furthermore, OM-85 increased the level of sACE2 (p < 0.05), hyaluronic acid (p < 0.002), and hyaluronan synthase 1 (p < 0.01). Consequently, the infection by a SARS-CoV-2 spike protein pseudo-typed lentivirus was reduced in cells pretreated with OM-85. All effects of OM-85 were concentration- and time-dependent. The results suggest that OM-85 might reduce the binding of SARS-CoV-2 S-protein to epithelial cells by modification of host cell membrane proteins and specific glycosaminoglycans. Thus, OM-85 might be considered as an add-on for COVID-19 therapy.

Atherosclerosis is a chronic immunoinflammatory disease associated with blood lipid disorders. Previous studies in mice have demonstrated that liver X receptor (LXR)‑ATP‑binding cassette (ABC) A1/ABCG1/C‑C chemokine receptor type 7 (CCR7) and nuclear factor κB (NF‑κB) signaling pathways are important for atherosclerotic plaque formation. In addition, Sirtuin 1 (SIRT1) has been reported as a key regulator in the protection from risk of atherosclerosis. However, the exact mechanism by which SIRT1 prevents atherosclerosis remains largely unknown. To explore the possible mechanisms, the expression of SIRT1 and the association between SIRT1, LXR and NF‑κB in the process of foam cell formation was investigated in an in vitro human mononuclear U937 cell line. Monocyte‑derived foam cells were induced by palmitate and Ox‑LDL treatment. Oil Red O staining revealed an accumulation of a large number of lipid droplets in foam cells. Results of reverse transcription polymerase chain reaction (RT-PCR) revealed that SIRT1 expression was downregulated during foam cell formation. In addition, the expression of LXRα and its targets, ABCA1, ABCG1 and CCR7, were downregulated. However, NF‑κB and its targets, tumor necrosis factor α (TNFα) and interleukin (IL)‑1β, were upregulated in foam cells. Following activation of SIRT1 by SRT1720, the expression of LXRα and its targets increased, whereas expression of NF‑κB and its targets decreased. Furthermore, the formation of foam cells was blocked. The SIRT1 inhibitor, nicotinamide, was found to eliminate the effects of SRT1720. Results of the present study indicate that SIRT1 may prevent the formation and progression of atherosclerosis by enhancing the LXR‑ABCA1/ABCG1/CCR7 and inhibiting the NF‑κB pathways.

These findings indicate that early administration of propofol may provide protective effects against endotoxin-induced acute lung injury.

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