Cytokine combinations for human blood stem cell expansion induce cell-type- and cytokine-specific signaling dynamics.

How hematopoietic stem cells (HSCs) integrate signals from their environment to make fate decisions remains incompletely understood. Current knowledge is based on either averages of heterogeneous populations or snapshot analyses, both missing important information about the dynamics of intracellular signaling activity. By combining fluorescent biosensors with time-lapse imaging and microfluidics, we measured the activity of the extracellular-signal-regulated kinase (ERK) pathway over time (ie, dynamics) in live single human umbilical cord blood HSCs and multipotent progenitor cells (MPPs). In single cells, ERK signaling dynamics were highly heterogeneous and depended on the cytokines, their combinations, and cell types. ERK signaling was activated by stem cell factor (SCF) and FMS-like tyrosine kinase 3 ligand in HSCs but SCF, interleukin 3, and granulocyte colony-stimulating factor in MPPs. Different cytokines and their combinations led to distinct ERK signaling dynamics frequencies, and ERK dynamics in HSCs were more transient than those in MPPs. A combination of 5 cytokines recently shown to maintain HSCs in long-term culture, had a more-than-additive effect in eliciting sustained ERK dynamics in HSCs. ERK signaling dynamics also predicted future cell fates. For example, CD45RA expression increased more in HSC daughters with intermediate than with transient or sustained ERK signaling. We demonstrate heterogeneous cytokine- and cell-type-specific ERK signaling dynamics, illustrating their relevance in regulating hematopoietic stem and progenitor (HSPC) cell fates.

Adult thymus contains FoxN1(-) epithelial stem cells that are bipotent for medullary and cortical thymic epithelial lineages.

Within the thymus, two major thymic epithelial cell (TEC) subsets-cortical and medullary TECs-provide unique structural and functional niches for T cell development and establishment of central tolerance. Both lineages are believed to originate from a common progenitor cell, yet the cellular and molecular identity of these bipotent TEC progenitors/stem cells remains ill defined. Here we identify rare stromal cells in the murine adult thymus, which under low-attachment conditions formed spheres (termed "thymospheres"). These thymosphere-forming cells (TSFCs) displayed the stemness features of being slow cycling, self-renewing, and bipotent. TSFCs could be significantly enriched based on their distinct surface antigen phenotype. The FoxN1 transcription factor was dispensable for TSFCs maintenance in situ and for commitment to the medullary and cortical TEC lineages. In summary, this study presents the characterization of the adult thymic epithelial stem cells and demonstrates the dispensability of FoxN1 function for their stemness.

"Ex-vivo" T-cell depletion in allogeneic hematopoietic stem cell transplantation: New clinical approaches for old challenges.

Allogeneic transplantation still remains as standard of care for patients with high-risk hematological malignancies at diagnosis or after relapse. However, GvHD remains yet as the most relevant clinical complication in the early post-transplant period. TCD allogeneic transplant is now considered a valid option to reduce severe GvHD and to provide a platform for cellular therapy to prevent relapse disease or to treat opportunistic infections.

Functional expression cloning of molecules inducing CD34 expression in bone marrow-derived stromal myofibroblasts.

We have previously shown a fraction of stromal fibroblasts/myofibroblasts (Fibs) from leukemic bone marrow cells expresses leukemia-specific transcripts along with hematopoietic and Fib-related markers. Normal bone marrow-derived Fibs (nFibs) do not express CD34 or CD45; however, nFibs may express hematopoietic markers with some specific stimulations. CD34 expression was detected in nFib cultures following the addition of a culture supernatant of blood mononuclear cells stimulated with phytohemagglutinin (PHA)-P. To identify the molecules responsible for inducing CD34 expression in nFibs, cDNA clones were isolated using functional expression cloning with a library constructed from PHA-P-stimulated human blood mononuclear cells. Positive clones inducing CD34 transcription in nFibs were selected. We confirmed that an isolated positive cDNA clone encoded human interleukin (IL)-1 beta (ß). CD34 expression was observed in the nFib cultures with recombinant human (rh) IL-1ß protein. And CD34 transcription was suppressed when a rhIL-1ß neutralizing antibody was added to the IL-1ß-stimulated nFib cultures. nFibs expressed gp130 and IL-6 receptors, and CD45 expression was detected in nFibs cultured with rhIL-1ß and rhIL-6. Chronic myelogenous leukemia (CML) cells reportedly respond well to IL-1ß. When CML-derived Fibs were cultured with rhIL-1ß and rhIL-6, CD45-positive cells increased in number. Cell fate may be influenced by an external specific stimulation without gene introduction.

Genetic loss of NFAT2 (NFATc1) impairs B cell development of B1 and B2 B cells.

NFAT2 activity was shown to be of critical importance in B cell receptor signaling, development and proliferation; however its role in B cell development in the periphery is still not completely understood. We confirmed that NFAT2 deletion leads to impaired B1 B cell development, supported by our finding of limited B1 progenitors in the bone marrow and spleen of NFAT2 deficient mice. Moreover, we show for the first time that loss of NFAT2 increases immature B cells in particular transitional T2 and T3 as well as mature follicular B cells while marginal zone B cells are decreased. We further demonstrate that NFAT2 regulates the expression of B220, CD23, CD38, IgM/IgD and ZAP70 in murine B cells. In vivo analyses revealed decreased proliferation and increased apoptosis of NFAT2 deficient B cells. In summary, this study provides an extensive analysis of the role of NFAT2 in peripheral B lymphocyte development.

Estradiol regulates the expression of CD45 splicing isoforms in lymphocytes.

CD45, a common leukocyte antigen expressed on the surface of all nucleated hematopoietic cells, indicates the developmental stage and functional status of lymphocytes by its alternative splicing isoforms. Estrogen is correlated with the immune activity of lymphocytes and is involved in the sex bias of several human autoimmune diseases, but the effect of estrogen on the expression of the CD45 splicing isoforms remains unknown. In the present study, a potential estrogen response element was identified on the opposite strand of the CD45 gene by bioinformatics software prediction. The results from RT-qPCR results showed that the expression levels of CD45RO isoform and CD45 antisense RNA were increased after the lymphocytes were treated with 10 nM 17beta-estradiol, and this effect of 17beta-estradiol was reversed when the lymphocytes were cotreated with an estrogen receptor antagonist. Moreover, bisulfite sequencing PCR showed that CD45 DNA methylation in lymphocytes was increased after the treatment with 10 nM 17beta-estradiol. In conclusion, estradiol regulated the expression of CD45 in an estrogen receptor-dependent manner and was associated with CD45 antisense RNA and DNA methylation. The results helped elucidate the regulatory mechanism of the expression of CD45 isoforms and the correlation between estrogen levels and immune activity in females.

The Mouse Cytomegalovirus Gene m42 Targets Surface Expression of the Protein Tyrosine Phosphatase CD45 in Infected Macrophages.

The receptor-like protein tyrosine phosphatase CD45 is expressed on the surface of cells of hematopoietic origin and has a pivotal role for the function of these cells in the immune response. Here we report that following infection of macrophages with mouse cytomegalovirus (MCMV) the cell surface expression of CD45 is drastically diminished. Screening of a set of MCMV deletion mutants allowed us to identify the viral gene m42 of being responsible for CD45 down-modulation. Moreover, expression of m42 independent of viral infection upon retroviral transduction of the RAW264.7 macrophage cell line led to comparable regulation of CD45 expression. In immunocompetent mice infected with an m42 deletion mutant lower viral titers were observed in all tissues examined when compared to wildtype MCMV, indicating an important role of m42 for viral replication in vivo. The m42 gene product was identified as an 18 kDa protein expressed with early kinetics and is predicted to be a tail-anchored membrane protein. Tracking of surface-resident CD45 molecules revealed that m42 induces internalization and degradation of CD45. The observation that the amounts of the E3 ubiquitin ligases Itch and Nedd4 were diminished in cells expressing m42 and that disruption of a PY motif in the N-terminal part of m42 resulted in loss of function, suggest that m42 acts as an activator or adaptor for these Nedd4-like ubiquitin ligases, which mark CD45 for lysosomal degradation. In conclusion, the down-modulation of CD45 expression in MCMV-infected myeloid cells represents a novel pathway of virus-host interaction.

CD45 Expression in Mitral Valve Endothelial Cells After Myocardial Infarction.

RATIONALE: Ischemic mitral regurgitation, a complication after myocardial infarction (MI), induces adaptive mitral valve (MV) responses that may be initially beneficial but eventually lead to leaflet fibrosis and MV dysfunction. We sought to examine the MV endothelial response and its potential contribution to ischemic mitral regurgitation. OBJECTIVE: Endothelial, interstitial, and hematopoietic cells in MVs from post-MI sheep were quantified. MV endothelial CD45, found post MI, was analyzed in vitro. METHODS AND RESULTS: Ovine MVs, harvested 6 months after inferior MI, showed CD45, a protein tyrosine phosphatase, colocalized with von Willebrand factor, an endothelial marker. Flow cytometry of MV cells revealed significant increases in CD45+ endothelial cells (VE-cadherin+/CD45+/α-smooth muscle actin [SMA]+ and VE-cadherin+/CD45+/αSMA- cells) and possible fibrocytes (VE-cadherin-/CD45+/αSMA+) in inferior MI compared with sham-operated and normal sheep. CD45+ cells correlated with MV fibrosis and mitral regurgitation severity. VE-cadherin+/CD45+/αSMA+ cells suggested that CD45 may be linked to endothelial-to-mesenchymal transition (EndMT). MV endothelial cells treated with transforming growth factor-ß1 to induce EndMT expressed CD45 and fibrosis markers collagen 1 and 3 and transforming growth factor-ß1 to 3, not observed in transforming growth factor-ß1-treated arterial endothelial cells. A CD45 protein tyrosine phosphatase inhibitor blocked induction of EndMT and fibrosis markers and inhibited EndMT-associated migration of MV endothelial cells. CONCLUSIONS: MV endothelial cells express CD45, both in vivo post MI and in vitro in response to transforming growth factor-ß1. A CD45 phosphatase inhibitor blocked hallmarks of EndMT in MV endothelial cells. These results point to a novel, functional requirement for CD45 phosphatase activity in EndMT. The contribution of CD45+ endothelial cells to MV adaptation and fibrosis post MI warrants investigation.

Maternal immune correlates of protection from human cytomegalovirus transmission to the fetus after primary infection in pregnancy.

Immune control of primary human cytomegalovirus (HCMV) infection appears to depend on the interaction of humoral and T-cell responses. In this review, we have separately explored the 2 arms of the immune response to primary HCMV infection in HCMV-seronegative pregnant women transmitting (T) or not transmitting (NT) the infection to the fetus, with the objective of correlating the immune risk factors associated with vertical HCMV transmission. As for the humoral response, the following findings were documented: (i) in competitive binding assays, antibody titers to different antigenic sites of the gH pentamer complex were significantly lower in T compared with NT women; (ii) in addition, the number of neutralization sites recognized by T was significantly lower compared with NT women; (iii) the plaque formation inhibition assay showed a faster kinetics and a higher titer in NT women. As for T-cell immunity, the delayed expression of 3 immunological parameters (lymphoproliferative response, CD45RA reexpression in both CD4+ and CD8+ HCMV-specific T cells, and interleukin-2 production by HCMV-specific CD4+ T cells) were significantly associated with vertical transmission. This overview provides important information at the population level, which may help to inform the evaluation of interventions such as vaccination or treatments designed to interrupt intrauterine transmission of HCMV during primary infection. However, although we are waiting for an HCMV vaccination to become available, we emphasize that none of these parameters can be prognostically used on an individual basis because of the great variation in values among women.

Probiotic bacteria prevent Salmonella - induced suppression of lymphoproliferation in mice by an immunomodulatory mechanism.

BACKGROUND: Salmonella enterica infections often exhibit a form of immune evasion. We previously observed that probiotic bacteria could prevent inhibition of lymphoproliferation and apoptosis responses of T cells associated with S. enterica infections in orally challenged mice. RESULTS: In this study, changes in expression of genes related to lymphocyte activation in mucosa-associated lymphoid tissues (MALT) of mice orally infected with S. enterica with and without treatment with probiotic bacteria were evaluated. Probiotic bacteria increased expression of mRNA for clusters of differentiation antigen 2 (Cd2), protein tyrosine phosphatase receptor type C (Ptprc), and Toll-like receptor 6 (Tlr6) genes related to T and B cell activation in mouse intestinal tissue. The probiotic bacteria were also associated with reduced mRNA expression of a group of genes (RelB, Myd88, Iκκa, Jun, Irak2) related to nuclear factor of kappa light chains enhancer in B cells (NF-κB) signal transduction pathway-regulated cytokine responses. Probiotic bacteria were also associated with reduced mRNA expression of apoptotic genes (Casp2, Casp12, Dad1, Akt1, Bad) that suggest high avidity lymphocyte sparing. Reduced CD2 immunostaining in mesenteric lymph nodes (MLN) was suggestive of reduced lymphocyte activation in probiotic-treated mice. Reduced immunostaining of TLR6 in MALT of probiotic-treated, S. enterica-infected mice suggests that diminished innate immune sensitivity to S. enterica antigens is associated with preventing lymphocyte deletion. CONCLUSIONS: The results of this study are consistent with prevention of S. enterica-induced deletion of lymphocytes by the influence of probiotic bacteria in mucosal lymphoid tissues of mice.

Identification of a reference gene for the quantification of mRNA and miRNA expression during skin wound healing.

AIM: Wound healing is a coordinated process to restore tissue homeostasis and reestablish the protective barrier of the skin. miRNAs may modulate the expression of target genes to contribute to repair processes, but due to the complexity of the tissue it is challenging to quantify gene expression during the distinct phases of wound repair. Here, we aimed to identify a common reference gene to quantify changes in miRNA and mRNA expression during skin wound healing. METHODS: Quantitative real-time PCR and bioinformatic analysis tools were used to identify suitable reference genes during skin repair and their reliability was tested by studying the expression of mRNAs and miRNAs. RESULTS: Morphological assessment of wounds showed that the injury model recapitulates the distinct phases of skin repair. Non-degraded RNA could be isolated from skin and wounds and used to study the expression of non-coding small nuclear RNAs during wound healing. Among those, RNU6B was most constantly expressed during skin repair. Using this reference gene we could confirm the transient upregulation of IL-1ß and PTPRC/CD45 during the early phase as well as the increased expression of collagen type I at later stages of repair and validate the differential expression of miR-204, miR-205, and miR-31 in skin wounds. In contrast to Gapdh the normalization to multiple reference genes gave a similar outcome. CONCLUSION: RNU6B is an accurate alternative normalizer to quantify mRNA and miRNA expression during the distinct phases of skin wound healing when analysis of multiple reference genes is not feasible.

The triterpenoid CDDO-imidazolide reduces immune cell infiltration and cytokine secretion in the KrasG12D;Pdx1-Cre (KC) mouse model of pancreatic cancer.

Because the 5-year survival rate for pancreatic cancer remains under 10%, new drugs are needed for the prevention and treatment of this devastating disease. Patients with chronic pancreatitis have a 12-fold higher risk of developing pancreatic cancer. LSL-KrasG12D/+;Pdx-1-Cre (KC) mice replicate the genetics, symptoms and histopathology found in human pancreatic cancer. Immune cells infiltrate into the pancreas of these mice and produce inflammatory cytokines that promote tumor growth. KC mice are particularly sensitive to the effects of lipopolysaccharide (LPS), as only 48% of KC mice survived an LPS challenge while 100% of wildtype (WT) mice survived. LPS also increased the percentage of CD45+ immune cells in the pancreas and immunosuppressive Gr1+ myeloid-derived suppressor cell in the spleen of these mice. The triterpenoid CDDO-imidazolide (CDDO-Im) not only reduced the lethal effects of LPS (71% survival) but also decreased the infiltration of CD45+ cells into the pancreas and the percentage of Gr1+ myeloid-derived suppressor cell in the spleen of KC mice 4-8 weeks after the initial LPS challenge. While the levels of inflammatory cytokine levels were markedly higher in KC mice versus WT mice challenged with LPS, CDDO-Im significantly decreased the production of IL-6, CCL-2, vascular endothelial growth factor and G-CSF in the KC mice. All of these cytokines are prognostic markers in pancreatic cancer or play important roles in the progression of this disease. Disrupting the inflammatory process with drugs such as CDDO-Im might be useful for preventing pancreatic cancer, especially in high-risk populations.

Aging has small effects on initial ischemic acute kidney injury development despite changing intrarenal immunologic micromilieu in mice.

Inflammatory process mediated by innate and adaptive immune systems is a major pathogenic mechanism of renal ischemia-reperfusion injury (IRI). There are concerns that organ recipients may be at increased risk of developing IRI after receiving kidneys from elder donors. To reveal the effects of aging on the development of renal IRI, we compared the immunologic micromilieu of normal and postischemic kidneys from mice of three different ages (9 wk, 6 mo, and 12 mo). There was a higher number of total T cells, especially effector memory CD4/CD8 T cells, and regulatory T cells in the normal kidneys of old mice. On day 2 after IRI, the proportion of necrotic tubules and renal functional changes were comparable between groups although old mice had a higher proportion of damaged tubule compared with young mice. More T cells, but less B cells, trafficked into the postischemic kidneys of old mice. The infiltration of NK T cells was similar across the groups. Macrophages and neutrophils were comparable between groups in both normal kidneys and postischemic kidneys. The intrarenal expressions of TNF-α and VEGF were decreased in normal and postischemic kidneys of aged mice. These mixed effects of aging on lymphocytes and cytokines/chemokines were not different between the two groups of old mice. Our study demonstrates that aging alters the intrarenal micromilieu but has small effects on the development of initial renal injury after IRI. Further study investigating aging-dependent differences in the repair process of renal IRI may be required.

Innate immune cell CD45 regulates lymphopenia-induced T cell proliferation.

The leukocyte-specific tyrosine phosphatase, CD45, severely impacts T cell development and activation by modulating TCR signaling. CD45-deficient (CD45KO) mice have reduced peripheral T cell numbers where CD8 T cells are underrepresented. In this article, we show that CD45KO mice are unable to support efficient homeostatic proliferation, affecting CD8 T cells more than CD4 T cells. Using CD45-RAG1 double-deficient (45RAGKO) mice, we show that lymphopenia-induced proliferation (LIP) of CD45-sufficient T cells is defective in a host environment lacking CD45 on innate immune cells. We identify two deficiencies in the 45RAGKO mice that affect LIP. One involves CD11c(+) cells and the second the production of IL-7 by lymphoid stromal cells. CD45KO dendritic cells were not defective in foreign Ag-induced T cell proliferation, yet CD45KO CD11c(+) cells were unable to rescue the spontaneous LIP in the 45RAGKO mice. This was in contrast with the CD45-sufficient CD11c(+) cells that partially rescued this spontaneous proliferation and did so without affecting IL-7 levels. The absence of CD45 also led to reduced IL-7 production by lymphoid stromal cells, suggesting an indirect effect of CD45 on innate immune cells in influencing IL-7 production by lymphoid stromal cells. These findings demonstrate a novel role for CD45 on innate immune cells in promoting lymphopenia-induced T cell proliferation and suggest that innate immune cells may communicate with stromal cells to regulate IL-7 production.

Modulation of renal ischemia/reperfusion in rats by a combination of ischemic preconditioning and adipose-derived mesenchymal stem cells (ADMSCs).

The present study investigated the effects of combination of ischemic preconditioning (Ipre) and adipose-derived mesenchymal stem cells (ADMSCs) on renal ischemia-reperfusion (I-R) injury in rats. 90 male Sprague Dawley rats were divided into 5 equal groups; sham operated, control (45 min left renal ischemia), Ipre group as control group with 3 cycles of Ipre just before renal ischemia, ADMSCs-treated group (as control with ADMSCs 10(6) cells in 0.1 mL via penile vein 60 min before ischemia time), and Ipre + ADMSCs group as ADMCs group with 3 cycles of Ipre. Ipre and ADMSCs groups showed significant decrease in serum creatinine and blood urea nitrogen (BUN) and caspase-3 and CD45 expression in kidney and significant increase in HIF-1α, SDF-1α, CD31, and Ki67 expressions in kidney compared with the control group (p < 0.05). Moreover, the Ipre + ADMSCs group showed significant decrease in serum BUN and caspase-3 and CD45 expression in kidney with significant increase in HIF-1α, SDF-1α, CD31, and Ki67 expression in kidney compared with the Ipre and ADMCs groups (p < 0.05). We concluded that Ipre potentiates the renoprotective effect of ADMSCs against renal I/R injury probably by upregulation of HIF-1α, SDF-1α, CD31, and Ki67 and downregulation of caspase-3 and CD45.

Side scatter versus CD45 flow cytometric plot can distinguish acute leukaemia subtypes.

BACKGROUND & OBJECTIVES: Flow cytometry is an important tool to diagnose acute leukaemia. Attempts are being made to find the minimal number of antibodies for correctly diagnosing acute leukaemia subtypes. The present study was designed to evaluate the analysis of side scatter (SSC) versus CD45 flow dot plot to distinguish acute myeloid leukaemia (AML) from acute lymphoblastic leukaemia (ALL), with minimal immunological markers. METHODS: One hundred consecutive cases of acute leukaemia were evaluated for blast cluster on SSC versus CD45 plots. The parameters studied included visual shape, CD45 and side scatter expression, continuity with residual granulocytes/lymphocytes/monocytes and ratio of maximum width to maximum height (w/h). The final diagnosis of ALL and AML and their subtypes was made by morphology, cytochemistry and immunophenotyping. Two sample Wilcoxon rank-sum (Mann Whitney) test and Kruskal-Wallis equality-of-populations rank tests were applied to elucidate the significance of the above ratios of blast cluster for diagnosis of ALL, AML and their subtypes. Receiver operating characteristic (ROC) curves were generated and the optimal cut-offs of the w/h ratio to distinguish between ALL and AML determined. RESULTS: Of the 100 cases, 57 of ALL and 43 cases of AML were diagnosed. The median w/h ratio of blast population was 3.8 for ALL and 1 for AML (P<0.001). ROC had area under curve of 0.9772.The optimal cut-off of the w/h ratio for distinction of ALL from AML was found to be 1.6. INTERPRETATION & CONCLUSIONS: Our findings suggest that if w/h ratio on SSC versus CD45 plot is less than 1.6, AML may be considered, and if it is more than 1.6, ALL may be diagnosed. Using morphometric analysis of the blast cluster on SSC versus CD45, it was possible to distinguish between ALL and AML, and their subtypes.

Abundance and specificity of influenza reactive circulating memory follicular helper and non-follicular helper CD4 T cells in healthy adults.

CD4 T-cell responses are functionally complex and regulate many aspects of innate and adaptive immunity. Follicular helper (Tfh) cells are CD4 T cells specialized to support B-cell production of isotype-switched, high-affinity antibody. So far, studies of Tfh cells in humans have focused on their differentiation requirements, with little research devoted to their antigen specificity. Here, after separating circulating human memory CD4 T cells based on expression of CXCR5, a signature marker of Tfh, we have quantified and assayed the influenza protein antigen specificity of blood Tfh cells and CD4 T cells lacking this marker. Through the use of peptide pools derived from nucleoprotein (NP) or haemagglutinin (HA) and a panel of human donors, we have discovered that circulating Tfh cells preferentially recognize peptide epitopes from HA while cells lacking CXCR5 are enriched for specificity toward NP. These studies suggest that reactive CD4 T cells specific for distinct viral antigens may have generalized differences in their functional potential due to their previous stimulation history.

Analysis of circulating tumor cells derived from advanced gastric cancer.

Studies in circulating tumor cells (CTCs) have proceeded to be accepted as prognostic markers in several types of cancers. But they are still limited because many are mainly from enumeration of CTCs. Here, we tried to evaluate the tumorigenicity of CTCs from advanced gastric cancer patients (n = 42). Peripheral blood mononuclear cells (PBMC) from the patients were separated into CD45 negative and positive fractions and both were subcutaneously injected into immunodeficient mice. Within 5 months nine tumor-like-structures from six patients but not from healthy volunteers were established. They were durable for passages and all had been confirmed human origin. Eight of the nine tumor-like-structures were from nonauthorized CTC containing cells expressing CD45 and B-cell markers. On the contrary, one of them was developed from CD45(-) PBMC fraction of a patient with bone marrow metastasis reflecting authorized CTCs. Histopathology showed common features with that of original gastric tumor. The cells isolated from the tumor-like-structure expressed EpCAM and CEA further supporting they were from the original tumor. Moreover the cells were CD44 positive to varying degree and a limiting dilution study showed that the CD44(+/high) fraction had tumorigenicity. The CD44 was dominantly in the form of CD44 variant 8-10. The CD44(+/high) cells had higher expression of the glutamate/cysteine transporter xCT compared with the CD44(-/low) cells. Our results showed the existence of tumor-initiating cells in blood of advanced gastric cancer patients and they could be a therapeutic target and prospective tool for further investigations.

Functional engraftment of human peripheral T and B cells and sustained production of autoantibodies in NOD/LtSzscid/IL-2Rγ(-/-) mice.

NOD/LtSzscid/IL-2Rγ(-/-) (NSG) mice have advantages in establishing humanized mouse models. However, transferring human PBMCs into these mice often causes lethal GVH disease. In this study, we discovered an improved method for the engraftment of normal or pathological human PBMCs into NSG mice and examined the subsequent induction of specific immune responses. We sequentially transferred human CD4+ memory T (Tm) and B cells obtained from PBMCs of healthy adults or patients with autoimmune diseases into NSG mice. Removing naïve CD4+ T cells from the transferred PBMCs allowed successful engraftment without lethal GVH disease. The transferred Tm cells were found to reside mainly in the spleen and the lymphoid nodules, where they expressed MHC class II molecules and produced cytokines, including IL-21. Surprisingly, the transferred B cells were also well maintained in the lymphoid organs, underwent de novo class-switch recombination, and secreted all isotypes of human Igs at significant levels. Moreover, transferring patient-derived Tm and B cells resulted in sustained production of IgM-rheumatoid factor and antiaminoacyl transfer RNA synthetase Abs in these mice. These results suggest that transfer of Tm and B cells derived from human PBMCs into NSG mice could be a useful method for the study of human autoimmune mechanisms.

Fine-tuning of regulatory T cell function: the role of calcium signals and naive regulatory T cells for regulatory T cell deficiency in multiple sclerosis.

The suppressor function of regulatory T cells (Tregs) is impaired in multiple sclerosis (MS), but the mechanisms underlying this deficiency are not fully understood. As Tregs counteract the sustained elevation of intracellular calcium, which is indispensable for full activation of conventional T cells (Tcons), we hypothesized that interference with this pathway might prompt MS-related Treg dysfunction. Using single-cell live imaging, we observed that Tregs rapidly reduce Ca(2+) influx and downstream signals in Tcons upon cell contact, yet differ in their potency to efficiently suppress several target cells at the same time. Strikingly, individual Tregs harboring a CD4(+)CD25(+)FOXP3(+)CD45RA(+) naive phenotype suppressed significantly more adjacent Tcons than did CD4(+)CD25(+)FOXP3(+)CD45RA(-) memory Tregs. Some constituents even completely failed to dampen Tcon Ca(2+) influx and were contained exclusively in the memory subset. In accordance with their more powerful suppressive performance, the Ca(2+) signature was considerably enhanced in naive Tregs in response to TCR triggering, compared with the memory counterparts. MS Tregs displayed a significantly diminished suppression of mean Ca(2+) influx in the sum of individual Tcons recorded. This reduced inhibitory activity was closely linked to decreased numbers of individual Tcons becoming suppressed by adjacent Tregs and, in turn, correlated with a marked reduction of naive subtypes and concomitant expansion of nonsuppressive memory phenotypes. We conclude that the superior achievement of naive Tregs is pivotal in maintaining Treg efficiency. As a consequence, MS Tregs become defective because they lack naive subtypes and are disproportionately enriched in memory cells that have lost their inherent downregulatory activity.