Benedikt Fritzsching

Reduced suppressive effect of CD4+CD25high regulatory T cells on the T cell immune response against myelin oligodendrocyte glycoprotein in patients with multiple sclerosis

Immunoregulatory T cells of CD4+CD25+ phenotype suppress T cell function and protect rodents from organ‐specific autoimmune disease. The human counterpart of this subset of T cells expresses high levels of CD25 and its role in human autoimmune disorders is currently under intense investigation. In multiple sclerosis (MS), a chronic inflammatory disease of the central nervous system (CNS), the activation of circulating self‐reactive T cells with specificity for myelin components is considered to be an important disease initiating event. Here, we investigated whether MS is associated with an altered ability of CD4+CD25high regulatory T cells (Treg) to confer suppression of myelin‐specific immune responses. Whereas Treg frequencies were equally distributed in blood and cerebrospinal fluid of MS patients and did not differ compared to healthy controls, the suppressive potency of patient‐derived CD4+CD25high T lymphocytes was impaired. Their inhibitory effect on antigen‐specific T cell proliferation induced by human recombinant myelin oligodendrocyte protein as well as on immune responses elicited by polyclonal and allogeneic stimuli was significantly reduced compared to healthy individuals. The effect was persistent and not due to responder cell resistance or altered survival of Treg, suggesting that a defective immunoregulation of peripheral T cells mediated by CD4+CD25high T lymphocytes promotes CNS autoimmunity in MS.

Prevalence of Newly Generated Naive Regulatory T Cells (Treg) Is Critical for Treg Suppressive Function and Determines Treg Dysfunction in Multiple Sclerosis

The suppressive function of regulatory T cells (Treg) is impaired in multiple sclerosis (MS) patients. The mechanism underlying the Treg functional defect is unknown. Treg mature in the thymus and the majority of cells circulating in the periphery rapidly adopt a memory phenotype. Because our own previous findings suggest that the thymic output of T cells is impaired in MS, we hypothesized that an altered Treg generation may contribute to the suppressive deficiency. We therefore determined the role of Treg that enter the circulation as recent thymic emigrants (RTE) and, unlike their CD45RO+ memory counterparts, express CD31 as typical surface marker. We show that the numbers of CD31+-coexpressing CD4+CD25+CD45RA+CD45RO−FOXP3+ Treg (RTE-Treg) within peripheral blood decline with age and are significantly reduced in MS patients. The reduced de novo generation of RTE-Treg is compensated by higher proportions of memory Treg, resulting in a stable cell count of the total Treg population. Depletion of CD31+ cells from Treg diminishes the suppressive capacity of donor but not patient Treg and neutralizes the difference in inhibitory potencies between the two groups. Overall, there was a clear correlation between Treg-mediated suppression and the prevalence of RTE-Treg, indicating that CD31-expressing naive Treg contribute to the functional properties of the entire Treg population. Furthermore, patient-derived Treg, but not healthy Treg, exhibit a contracted TCR Vβ repertoire. These observations suggest that a shift in the homeostatic composition of Treg subsets related to a reduced thymic-dependent de novo generation of RTE-Treg with a compensatory expansion of memory Treg may contribute to the Treg defect associated with MS.

Release and Intercellular Transfer of Cell Surface CD81 Via Microparticles

The human tetraspan molecule CD81 is a coreceptor in B and T cell activation and a candidate receptor for hepatitis C virus infection. We examined the surface expression of CD81 on B and T lymphocytes by quantitative flow cytometry. Upon cellular activation, CD81 surface levels were rapidly reduced. This reduction occurred as early as 1 h after activation and was linked to the release of CD81-positive microparticles into the cell culture medium. CD81 mRNA levels were not affected early after activation, but the release of CD81-positive microparticles was rapidly enhanced. In addition, intercellular transfer of CD81 was observed upon coculture of CD81-positive donor cells (Jurkat T cell line) with CD81-negative acceptor cells (U937 promonocytic cell line). This transfer was rapidly increased upon T cell activation, coinciding with enhanced CD81 release from activated Jurkat cells. We propose that the release and intercellular trafficking of CD81-positive microparticles regulate the expression of CD81 surface receptors in lymphocytes and play a role in the immune response during infections.

Glatiramer acetate improves regulatory T-cell function by expansion of naive CD4(+)CD25(+)FOXP3(+)CD31(+) T-cells in patients with multiple sclerosis.

Naturally occurring regulatory T-cells (Treg) exhibit impaired function in patients with relapsing-remitting multiple sclerosis (RRMS) resulting from an age-inappropriate disproportion between prevalences of newly generated CD31-coexpressing naive Treg and long-lived memory Treg in the periphery. Recent evidence suggests that the immunomodulatory action of glatiramer acetate (GA) includes effects on Treg function and frequencies. We prospectively assessed suppressive activities and frequencies of Treg and Treg subsets in 15 patients with RRMS undergoing long-term therapy with GA. Treatment for up to six months reconstituted naive Treg and increased total Treg numbers with concomitant reversion of the Treg defect.

Interferon Beta–Induced Restoration of Regulatory T-Cell Function in Multiple Sclerosis Is Prompted by an Increase in Newly Generated Naive Regulatory T Cells

BACKGROUND Naturally occurring regulatory T (T(reg)) cells are functionally impaired in patients with relapsing-remitting multiple sclerosis. We recently showed that prevalences of newly generated CD31-coexpressing naive T(reg) cells (recent thymic emigrant-T(reg) cells) are critical for suppressive function of circulating T(reg) cells, and a shift in the homeostatic composition of T(reg)-cell subsets related to a reduced de novo generation of recent thymic emigrant-T(reg) cells may contribute to the multiple sclerosis (MS)-related T(reg)-cell dysfunction. Interferon beta, an immunomodulatory agent with established efficacy in MS, lowers relapse rates and slows disease progression. Emerging evidence suggests that T(reg)-cell suppressive capacity may increase in patients with MS undergoing treatment with interferon beta, although the mechanisms mediating this effect are uncertain. OBJECTIVE To evaluate the effect of interferon beta treatment on the suppressive activity and the homeostasis of circulating T(reg) cells in patients with MS. PARTICIPANTS Twenty patients with relapsing-remitting MS and 18 healthy control subjects. INTERVENTIONS Administration of interferon beta. MAIN OUTCOME MEASURES Effect of interferon beta on T(reg)-cell homeostasis and suppressive capacity. RESULTS Suppressive capacities of T(reg) cells were consistently upregulated at 3 and 6 months after treatment with interferon beta. The restoration of T(reg)-cell function was paralleled by increased naive recent thymic emigrant-T(reg) cells and a coincidental reduction in memory T(reg) cells. CONCLUSION The increase in T(reg)-cell inhibitory capacity mediated by interferon beta treatment can be explained by its effect on the homeostatic balance within the T(reg) cell compartment.

Intracerebral Human Regulatory T Cells: Analysis of CD4+CD25+FOXP3+ T Cells in Brain Lesions and Cerebrospinal Fluid of Multiple Sclerosis Patients

Impaired suppressive capacity of CD4+CD25+FOXP3+ regulatory T cells (Treg) from peripheral blood of patients with multiple sclerosis (MS) has been reported by multiple laboratories. It is, however, currently unresolved whether Treg dysfunction in MS patients is limited to reduced control of peripheral T cell activation since most studies analyzed peripheral blood samples only. Here, we assessed early active MS lesions in brain biopsies obtained from 16 patients with MS by FOXP3 immunohistochemistry. In addition, we used six-color flow cytometry to determine numbers of Treg by analysis of FOXP3/CD127 expression in peripheral blood and cerebrospinal fluid (CSF) of 17 treatment-naïve MS patients as well as quantities of apoptosis sensitive CD45ROhiCD95hi cells in circulating and CSF Treg subsets. Absolute numbers of FOXP3+ and CD4+ cells were rather low in MS brain lesions and Treg were not detectable in 30% of MS biopsies despite the presence of CD4+ cell infiltrates. In contrast, Treg were detectable in all CSF samples and Treg with a CD45ROhiCD95hi phenotype previously shown to be highly apoptosis sensitive were found to be enriched in the CSF compared to peripheral blood of MS patients. We suggest a hypothetical model of intracerebral elimination of Treg by CD95L-mediated apoptosis within the MS lesion.

CD8+/FOXP3+-ratio in osteosarcoma microenvironment separates survivors from non-survivors: A multicenter validated retrospective study

Osteosarcoma is the most common primary bone tumor characterized by juvenile onset, tumor heterogeneity, and early pulmonary metastasis. Therapeutic improvement stagnates since more than two decades. Unlike major malignancies, biomarkers as prognostic factors at time of diagnosis are missing. Disease rareness hampers study recruitment of patient numbers sufficient to outweigh tumor heterogeneity. Here, we analyzed in a multicenter cohort the osteosarcoma microenvironment to reduce effects of tumor cell heterogeneity. We hypothesized that quantitative ratios of intratumoral CD8+T-cells to FOXP3+T-cells (CD8+/FOXP3+-ratios) provide strong prognostic information when analyzed by whole-slide imaging in diagnostic biopsies. We followed recommendations-for-tumor-marker-prognostic-studies (REMARK). From 150 included cases, patients with complete treatment were identified and assigned to the discovery (diagnosis before 2004) or the validation cohort (diagnosis 2004–2012). Highly standardized immunohistochemistry of CD8+ and FOXP3+, which was validated by methylation-specific gene analysis, was performed followed by whole-slide analysis and clinical outcome correlations. We observed improved estimated survival in patients with CD8+/FOXP3+-ratios above the median (3.08) compared to patients with lower CD8+/FOXP3+-ratios (p = 0.000001). No patients with a CD8+/FOXP3+-ratio above the third quartile died within the observation period (median follow-up 69 mo). Multivariate analysis demonstrated independence from current prognostic factors including metastasis and response to neoadjuvant chemotherapy. Data from an independent validation cohort confirmed improved survival (p = 0.001) in patients with CD8+/FOXP3+-ratios above 3.08. Multivariate analysis proofed that this observation was also independent from prognostic factors at diagnosis within the validation cohort. Intratumoral CD8+/FOXP3+-ratio in pretreatment biopsies separates patients with prolonged survival from non-survivors in osteosarcoma.

Regulatory T-cell impairment in cystic fibrosis patients with chronic pseudomonas infection.

RATIONALE Patients with cystic fibrosis (CF) lung disease have chronic airway inflammation driven by disrupted balance of T-cell (Th17 and Th2) responses. Regulatory T cells (Tregs) dampen T-cell activation, but their role in CF is incompletely understood. OBJECTIVES To characterize numbers, function, and clinical impact of Tregs in CF lung disease. METHODS Tregs were quantified in peripheral blood and airway samples from patients with CF and from lung disease control patients without CF and healthy control subjects. The role of Pseudomonas aeruginosa and CF transmembrane conductance regulator (CFTR) in Treg regulation was analyzed by using in vitro and murine in vivo models. MEASUREMENTS AND MAIN RESULTS Tregs were decreased in peripheral blood and airways of patients with CF compared with healthy controls or lung disease patients without CF and correlated positively with lung function parameters. Patients with CF with chronic P. aeruginosa infection had lower Tregs compared with patients with CF without P. aeruginosa infection. Genetic knockout, pharmacological inhibition, and P. aeruginosa infection studies showed that both P. aeruginosa and CFTR contributed to Treg dysregulation in CF. Functionally, Tregs from patients with CF or from Cftr(-/-) mice were impaired in suppressing conventional T cells, an effect that was enhanced by P. aeruginosa infection. The loss of Tregs in CF affected memory, but not naive Tregs, and manifested gradually with disease progression. CONCLUSIONS Patients with CF who have chronic P. aeruginosa infection show an age-dependent, quantitative, and qualitative impairment of Tregs. Modulation of Tregs represents a novel strategy to rebalance T-cell responses, dampen inflammation, and ultimately improve outcomes for patients with infective CF lung disease.

T-cell homeostasis in pediatric multiple sclerosis Old cells in young patients

Objective: To assess pediatric patients with multiple sclerosis (MS) for early signs of homeostatic and functional abnormalities in conventional (Tcon) and regulatory T cells (Treg). Methods: We studied the composition of the peripheral T-cell compartment and Treg function in a cross-sectional study with 30 pediatric MS (pMS) patients by multicolor flow cytometry and proliferation assays. Data were compared to those obtained from adult patients (n = 26) and age-matched control donors (n = 67). Results: Proportions of naive T cells were 10%–20% higher in children than in adults, reflecting the age-related decline. pMS patients, however, had clearly lower numbers of naive T cells, among them recent thymic emigrants (RTE), whereas percentages of memory T cells were increased. In the Treg compartment, reduced RTE numbers coincided with markedly dampened suppressive capacities of total Treg. These homeostatic changes in circulating T cells precisely paralleled the pattern seen in adult MS. As in adults, treatment with immunomodulatory drugs attenuated these alterations. Conclusion: The homeostatic changes detected in the T-cell compartment in pMS are similar to those in adult-onset disease. With ratios between naive and memory T-cell subsets matching those of 20- to 30-years-older controls, signs of early thymic involution are already found in pMS, suggesting that an intrinsic compromise in thymic-dependent T-cell neogenesis might contribute to MS pathogenesis.

Similar sensitivity of regulatory T cells towards CD95L-mediated apoptosis in patients with multiple sclerosis and healthy individuals

Impaired suppressive function of CD4(+)CD25(high) regulatory T cells (T(reg)) has been reported as a novel pathogenetic mechanism in Multiple sclerosis (MS). We addressed if high apoptosis sensitivity of MS-T(reg) could explain this functional T(reg) defect. T(reg) from treatment-naïve MS patients showed high sensitivity towards CD95Ligand-mediated apoptosis and exhibited enhanced cell death to IL-2 and TCR-signal deprivation. Since susceptibility of T(reg) to cell death was similar in MS patients and healthy controls, this cannot explain the inhibitory dysfunction of T(reg) associated with MS. Furthermore, as cell death is not enhanced, therapeutic expansion of MS-T(reg)in vitro should be a reasonable and novel therapeutic option.