The role of immune reconstitution in relapse after allogeneic hematopoietic stem cell transplantation.

INTRODUCTION: Leukemia relapse following stem cell transplantation remains a significant barrier to long-term remission. Timely and balanced immune recovery after transplantation is crucial for preventing leukemia relapse. AREAS COVERED: After an extensive literature search of PubMed and Web of Science through October 2023, we provide an overview of the dynamics of immune reconstitution and its role in controlling leukemia relapse. We also discuss strategies to promote immune reconstitution and reduce disease recurrence following allogeneic hematopoietic stem cell transplantation. EXPERT OPINION: Immune reconstitution after transplantation has substantial potential to prevent relapse and might predict disease recurrence and prognosis. High dimensional cytometry, multi-omics, and T cell repertoire analysis allow for a more comprehensive and detailed understanding of the immune system's dynamics post-transplantation, and contribute to the identification of rare immune cell subsets or potential biomarkers associated with successful immune reconstitution or increased risk of complications. Strategies to enhance the immune system, such as adoptive immunotherapy and cytokine-based therapy, have great potential for reducing leukemia relapse after transplantation. Future research directions should focus on refining patient selection for these therapies, implementing appropriate and timely treatment, investigating combination approaches to maximize therapeutic outcomes, and achieving a robust graft-versus-leukemia (GVL) effect while minimizing graft-versus-host disease (GVHD) for optimal results.

Modulation of cytomegalovirus immune evasion identifies direct antigen presentation as the predominant mode of CD8 T-cell priming during immune reconstitution after hematopoietic cell transplantation.

Cytomegalovirus (CMV) infection is the most critical infectious complication in recipients of hematopoietic cell transplantation (HCT) in the period between a therapeutic hematoablative treatment and the hematopoietic reconstitution of the immune system. Clinical investigation as well as the mouse model of experimental HCT have consistently shown that timely reconstitution of antiviral CD8 T cells is critical for preventing CMV disease in HCT recipients. Reconstitution of cells of the T-cell lineage generates naïve CD8 T cells with random specificities among which CMV-specific cells need to be primed by presentation of viral antigen for antigen-specific clonal expansion and generation of protective antiviral effector CD8 T cells. For CD8 T-cell priming two pathways are discussed: "direct antigen presentation" by infected professional antigen-presenting cells (pAPCs) and "antigen cross-presentation" by uninfected pAPCs that take up antigenic material derived from infected tissue cells. Current view in CMV immunology favors the cross-priming hypothesis with the argument that viral immune evasion proteins, known to interfere with the MHC class-I pathway of direct antigen presentation by infected cells, would inhibit the CD8 T-cell response. While the mode of antigen presentation in the mouse model of CMV infection has been studied in the immunocompetent host under genetic or experimental conditions excluding either pathway of antigen presentation, we are not aware of any study addressing the medically relevant question of how newly generated naïve CD8 T cells become primed in the phase of lympho-hematopoietic reconstitution after HCT. Here we used the well-established mouse model of experimental HCT and infection with murine CMV (mCMV) and pursued the recently described approach of up- or down-modulating direct antigen presentation by using recombinant viruses lacking or overexpressing the central immune evasion protein m152 of mCMV, respectively. Our data reveal that the magnitude of the CD8 T-cell response directly reflects the level of direct antigen presentation.

The impact of omidubicel on immune reconstitution and infections in cord blood transplant patients.

INTRODUCTION: The success of an allogeneic hematopoietic stem cell transplantation (alloHCT) is measured by cure from the underlying malignancy, immune reconstitution (IR), and freedom from graft-versus-host disease, without the continued need for immunosuppressive therapy. AREAS COVERED: Effective IR is critical to the success of alloHCT wherein poor IR can potentially increase the risk of infection and disease relapse. Different stem cell sources give rise to varying patterns of IR. Particularly with umbilical cord blood transplant, delayed IR is commonly seen with associated increased infection rates and non-relapse mortality, attributable to low CD34+ cell doses and predominance of naïve T cells in the graft. Recent FDA approval of omidubicel, an expanded cord blood graft, was granted due to rapid hematologic recovery and a reduced incidence of high-grade infections associated with improved IR. This review focuses on IR and infections seen with omidubicel and compares those to IR after alloHCT with other graft sources. EXPERT OPINION: Characteristics of omidubicel, such as ready availability, high infused CD34+ cell dose, and rapid hematologic and immune recovery improve upon the shortcomings of standard umbilical cord blood transplantation. We feel that the data support the emergence of omidubicel as an alternative donor product.

[Immune Reconstitution after BTKi Treatment in Chronic Lymphocytic Leukemia].

OBJECTIVE: To analyze the immune reconstitution after BTKi treatment in patients with chronic lymphocytic leukemia (CLL). METHODS: The clinical and laboratorial data of 59 CLL patients admitted from January 2017 to March 2022 in Fujian Medical University Union Hospital were collected and analyzed retrospectively. RESULTS: The median age of 59 CLL patients was 60.5(36-78). After one year of BTKi treatment, the CLL clones (CD5 +/CD19 +) of 51 cases (86.4%) were significantly reduced, in which the number of cloned-B cells decreased significantly from (46±6.1)×109/L to (2.3±0.4)×109/L (P =0.0013). But there was no significant change in the number of non-cloned B cells (CD19 + minus CD5 +/CD19 +). After BTKi treatment, IgA increased significantly from (0.75±0.09)g/L to (1.31±0.1)g/L (P <0.001), while IgG and IgM decreased from (8.1±0.2)g/L and (0.52±0.6)g/L to (7.1±0.1)g/L and (0.47±0.1)g/L, respectively (P <0.001, P =0.002). BTKi treatment resulted in a significant change in T cell subpopulation of CLL patients, which manifested as both a decrease in total number of T cells from (2.1±0.1)×109/L to (1.6±0.4)×109/L and NK/T cells from (0.11±0.1)×109/L to (0.07±0.01)×109/L (P =0.042, P =0.038), both an increase in number of CD4 + cells from (0.15±6.1)×109/L to (0.19±0.4)×109/L and CD8 + cells from (0.27±0.01)×109/L to (0.41±0.08)×109/L (both P <0.001). BTKi treatment also up-regulated the expression of interleukin (IL)-2 while down-regulated IL-4 and interferon (IFN)-γ. However, the expression of IL-6, IL-10, and tumor necrosis factor (TNF)-α did not change significantly. BTKi treatment could also restored the diversity of TCR and BCR in CLL patients, especially obviously in those patients with complete remission (CR) than those with partial remission (PR). Before and after BTKi treatment, Shannon index of TCR in patients with CR was 0.02±0.008 and 0.14±0.001 (P <0.001), while in patients with PR was 0.01±0.03 and 0.05±0.02 (P >0.05), respectively. Shannon index of BCR in patients with CR was 0.19±0.003 and 0.33±0.15 (P <0.001), while in patients with PR was 0.15±0.009 and 0.23±0.18 (P <0.05), respectively. CONCLUSIONS: BTKi treatment can shrink the clone size in CLL patients, promote the expression of IgA, increase the number of functional T cells, and regulate the secretion of cytokines such as IL-2, IL-4, and IFN-γ. BTKi also promote the recovery of diversity of TCR and BCR. BTKi treatment contributes to the reconstitution of immune function in CLL patients.

Early M-protein immune reconstitution after autologous haematopoietic stem cell transplantation is a good prognostic marker for patients with high-risk cytogenetic multiple myeloma.

The presence of transient abnormal protein banding (M-protein immune reconstitution) in serum immunofixation electrophoresis after autologous haematopoietic stem cell transplantation in patients with multiple myeloma has been reported. The purpose of this study was to investigate the impact of post-transplant M-protein immune reconstitution on the prognosis of patients with multiple myeloma. M-protein immune reconstitution was observed in 25.9% (75/290) of patients. The CR rate and MRD negativity were higher in the M-protein immune reconstitution group (85.3% vs. 69.3%, p = 0.013, 81.9% vs. 66.5%, p = 0.014). Although there were no significant differences between the groups, the overall median survival time was longer in the M-protein immune reconstruction group (80 vs. 72 m, p = 0.076; not reached vs. 105 m, p = 0.312). Among patients in the cytogenetic high-risk group, the occurrence of M-protein immune reconstitution predicted better PFS and OS (80 vs. 31 m, p = 0.010; not reached vs. 91 m, p = 0.026). Additionally, in revised-International Staging System stage III patients, PFS and OS were better in those who achieved M-protein immune reconstitution (80 vs. 20 m, p = 0.025; 57 vs. 32 m, p = 0.103). The better prognosis of M-protein immune reconstitution patients may be associated with the acquisition of a deeper response. In high-risk patients, early acquisition of M-protein immune reconstitution may suggest a better prognosis.

Plasma Cytokine Expression and Immune Reconstitution in Early and Delayed Anti-HIV 96-Weeks Treatment: A Retrospective Study.

HIV is an immunodeficiency disease with emergence of inadequate corresponding reconstruction therapies. Pyroptosis of CD4+T cell is mainly caused by immune activation and inflammation that cannot be reduced by successful antiretroviral therapy (ART) alone. Coinfections because of CD4+T cell reconstitution failure can occur. Anti-inflammatory treatment determines the success of immune reconstitution. In our experiment, only a few cytokines could recover to normal level following a 2-year antiretroviral treatment in early ART initiation, which is consistent with current findings about adjuvant HIV anti-inflammatory therapy. Early infection is often accompanied by a more severe inflammatory response. Innate immunity cytokines like granulocyte macrophage-colony stimulating factor, IFN-γ induced protein 10 kDa, and tumor necrosis factor-α exhibited the most elevated levels among all kinds of inflammatory cytokines. The correlation analysis showed at least eight cytokines contributing to the changes of CD4/CD8 ratio.

Comorbidity of Myasthenia gravis and Graves' disease as immune reconstitution-associated autoimmune disease in HIV infection: A case report and literature review.

BACKGROUND: Comorbidity of Myasthenia gravis (MG) and Graves' disease (GD) in treated HIV-infected individuals has rarely been described and little study has been done on the link between HIV-related immune reconstitution and autoimmune diseases occurring post antiretroviral therapy. CASE PRESENTATION: Here we report on a 33-year-old Chinese man with HIV infection who had been virologically suppressed since 2018. The patient was diagnosed with GD and was treated in 2020. Early in 2022, he developed fluctuating weakness and fatigue involving the bilateral extraocular muscles and limbs. With a positive neostigmine test, he was considered to have MG, but showed a poor response to oral medication. After multiple failed medication attempts, a thymectomy was finally performed to resolve his symptoms. The consecutive onset of immunological events may have partially resulted from immune reconstitution after viral control. CONCLUSIONS: This is a rare case of HIV-related immune reconstitution-associated autoimmune disease (IRAD) with comorbidity of MG and GD which was reported initially. Cooperation with multidisciplinary teams is essential to avoid misdiagnosis and to promote the overall health of HIV-infected patients.

Development and Evaluation of a Nomogram for Predicting the Outcome of Immune Reconstitution Among HIV/AIDS Patients Receiving Antiretroviral Therapy in China.

This study aims to develop and evaluate a model to predict the immune reconstitution among HIV/AIDS patients after antiretroviral therapy (ART). A total of 502 HIV/AIDS patients are randomized to the training cohort and evaluation cohort. Least absolute shrinkage and selection operator (LASSO) regression and multivariate logistic regression analysis are performed to identify the indicators and establish the nomogram for predicting the immune reconstitution. Decision curve analysis (DCA) and clinical impact curve (CIC) are used to evaluate the clinical effectiveness of the nomogram. Predictive factors included white blood cells (WBC), baseline CD4+ T-cell counts (baseline CD4), ratio of effector regulatory T cells to resting regulatory T cells (eTreg/rTreg) and low-density lipoprotein cholesterol (LDL-C) and are incorporated into the nomogram. The area under the curve (AUC) is 0.812 (95% CI, 0.767∼0.851) and 0.794 (95%CI, 0.719∼0.857) in the training cohort and evaluation cohort, respectively. The calibration curve shows a high consistency between the predicted and actual observations. Moreover, DCA and CIC indicate that the nomogram has a superior net benefit in predicting poor immune reconstitution. A simple-to-use nomogram containing four routinely collected variables is developed and internally evaluated and can be used to predict the poor immune reconstitution in HIV/AIDS patients after ART.

Hematopoiesis and immune reconstitution after CD19 directed chimeric antigen receptor T-cells (CAR-T): A comprehensive review on incidence, risk factors and current management.

Impaired function of hematopoiesis after treatment with chimeric antigen T-cells (CAR-T) is a frequent finding and can interest a wide range of patients, regardless of age and underlying disease. Trilinear cytopenias, as well as hypogammaglobulinemia, B-cell aplasia, and T-cell impairment, can severely affect the infectious risk of CAR-T recipients, as well as their quality of life. In this review, we provide an overview of defects in hematopoiesis after CAR-T, starting with a summary of different definitions and thresholds. We then move to summarize the main pathogenetic mechanisms of cytopenias, and we offer insight into cytomorphological aspects, the role of clonal hematopoiesis, and the risk of secondary myeloid malignancies. Subsequently, we expose the major findings and reports on T-cell and B-cell quantitative and functional impairment after CAR-T. Finally, we provide an overview of current recommendations and leading experiences regarding the management of cytopenias and defective B- and T-cell function.

Gender and the length of time since autologous hematopoietic stem cell transplantation-What is their influence on the immune reconstitution in multiple myeloma patients?

INTRODUCTION: In the literature there is lack of information on the influence of gender and time since autologous hematopoietic stem cell transplantation (HSCT) on the immune reconstitution in multiple myeloma (MM) patients. OBJECTIVE: The aim of this study was to assess the diversity of the immune reconstitution according to gender in MM patients after autologous HSCT on the day of the clinic discharge and on the 29th day after discharge, as well as to investigate the changes in the immune system in females and males after staying at home for 28 days. METHOD: The studied population comprised 13 females and 13 males after autologous HSCT. On the day of the clinic discharge and on the 29th day after discharge blood samples were taken to analyse 22 immunological parameters. Statistical analysis was performed using STATISTICA 10 StatSoft Poland. For multiple comparisons, the Bonferroni correction was used. RESULTS: No statistically significant differences were observed in the analysed immunological parameters between the studied females and males with MM on the day of the clinic discharge and on the 29th day after discharge. However, on the 29th day after the clinic discharge compared to the day of the clinic discharge, statistically significant differences were found in 8 immunological parameters among females and 6 immunological parameters among males. CONCLUSION AND RECOMMENDATION: Our results indicate that the immune reconstitution is similar but not the same in patients of both genders. Statistically significant differences in the immune response in the studied females and males imply that gender may play a role in the immune reconstitution and that the results obtained in MM patients should be analysed separately in females and males. In order to explain the observed changes in the immune system according to gender, further research should be carried out on a larger population. This would most probably make it possible to find their clinical application.

Inhibition of RIP1 improves immune reconstitution and reduces GVHD mortality while preserving graft-versus-leukemia effects.

Graft-versus-host disease (GVHD) remains the major cause of morbidity and nonrelapse mortality (NRM) after hematopoietic cell transplantation (HCT). Inflammatory cytokines mediate damage to key GVHD targets such as intestinal stem cells (ISCs) and also activate receptor interacting protein kinase 1 (RIP1; RIPK1), a critical regulator of apoptosis and necroptosis. We therefore investigated the role of RIP1 in acute GVHD using samples from HCT patients, modeling GVHD damage in vitro with both human and mouse gastrointestinal (GI) organoids, and blocking RIP1 activation in vivo using several well-characterized mouse HCT models. Increased phospho-RIP1 expression in GI biopsies from patients with acute GVHD correlated with tissue damage and predicted NRM. Both the genetic inactivation of RIP1 and the RIP1 inhibitor GNE684 prevented GVHD-induced apoptosis of ISCs in vivo and in vitro. Daily administration of GNE684 for 14 days reduced inflammatory infiltrates in three GVHD target organs (intestine, liver, and spleen) in mice. Unexpectedly, GNE684 administration also reversed the marked loss of regulatory T cells in the intestines and liver during GVHD and reduced splenic T cell exhaustion, thus improving immune reconstitution. Pharmacological and genetic inhibition of RIP1 improved long-term survival without compromising the graft-versus-leukemia (GVL) effect in lymphocytic and myeloid leukemia mouse models. Thus, RIP1inhibition may represent a nonimmunosuppressive treatment for GVHD.

Dominant CD4+ T cell receptors remain stable throughout antiretroviral therapy-mediated immune restoration in people with HIV.

In people with HIV (PWH), the post-antiretroviral therapy (ART) window is critical for immune restoration and HIV reservoir stabilization. We employ deep immune profiling and T cell receptor (TCR) sequencing and examine proliferation to assess how ART impacts T cell homeostasis. In PWH on long-term ART, lymphocyte frequencies and phenotypes are mostly stable. By contrast, broad phenotypic changes in natural killer (NK) cells, γδ T cells, B cells, and CD4+ and CD8+ T cells are observed in the post-ART window. Whereas CD8+ T cells mostly restore, memory CD4+ T subsets and cytolytic NK cells show incomplete restoration 1.4 years post ART. Surprisingly, the hierarchies and frequencies of dominant CD4 TCR clonotypes (0.1%-11% of all CD4+ T cells) remain stable post ART, suggesting that clonal homeostasis can be independent of homeostatic processes regulating CD4+ T cell absolute number, phenotypes, and function. The slow restoration of host immunity post ART also has implications for the design of ART interruption studies.

The role of pyroptosis in incomplete immune reconstitution among people living with HIV：Potential therapeutic targets.

Globally, HIV infection causes significant morbidity and mortality, and is a major public health problem. Despite the fact that widespread use of antiretroviral therapy (ART) has substantially altered the natural history of HIV infection from originally being a universally lethal disease to now being a chronic medical condition for those taking appropriate treatment, approximately 10-40% of people living with HIV (PLWH) who take effective ART and maintain long-term viral suppression fail to achieve normalization of CD4 + T-cell counts. This phenomenon is referred to as incomplete immune reconstitution or immunological non-response. Although the precise mechanisms underlying this outcome have not been elucidated, recent evidence indicates that excessive pyroptosis may play a crucial role in the development of incomplete immune reconstitution. Pyroptosis is characterized by the formation of pores in the cell membrane, cell rupture, and secretion of intracellular contents and pro-inflammatory cytokines, including IL-1ß and IL-18. This excessive inflammation-induced programmed cell death leads to a massive loss of CD4 + T-cells, and inflammatory consequences that may promote and sustain incomplete immune reconstitution. Herein, we review the possible pathways activated in HIV infection by inflammasomes that act as switches of pyroptosis, and the role of pyroptosis in HIV, as well as the relevance of CD4 + T-cells in incomplete immune reconstitution. We also highlight the possible mechanisms of pyroptosis involved in incomplete immune reconstitution, thus paving the way for the development of potential targets for the treatment of incomplete immune reconstitution.

Current knowledge of the immune reconstitution inflammatory syndrome in Whipple disease: a review.

Immune reconstitution inflammatory syndrome (IRIS) is characterized by exaggerated and dysregulated inflammatory responses that occur as a result of reconstitution of adaptive or innate immunity. A wide range of microorganisms have been found to be associated with IRIS, such as human immunodeficiency virus (HIV), Mycobacterium and actinobacteria. Whipple disease (WD) is an infectious disorder caused by the Gram-positive bacterium Tropheryma whipplei (T. whipplei) and IRIS also serves as a complication during its treament. Although many of these pathological mechanisms are shared with related inflammatory disorders, IRIS in WD exhibits distinct features and is poorly described in the medical literature. Novel investigations of the intestinal mucosal immune system have provided new insights into the pathogenesis of IRIS, elucidating the interplay between systemic and local immune responses. These insights may be used to identify monitoring tools for disease prevention and to develop treatment strategies. Therefore, this review synthesizes these new concepts in WD IRIS to approach the feasibility of manipulating host immunity and immune reconstitution of inflammatory syndromes from a newer, more comprehensive perspective and study hypothetical options for the management of WD IRIS.

CD70-induced differentiation of proinflammatory Th1/17/22/GM lymphocytes associated with disease progression and immune reconstitution during HIV infection.

Immune overactivation is a hallmark of chronic HIV infection, which is critical to HIV pathogenesis and disease progression. The imbalance of helper T cell (Th) differentiation and subsequent cytokine dysregulation are generally considered to be the major drivers of excessive activation and inflammatory disorders in HIV infection. However, the accurate factors driving HIV-associated Th changes remained to be established. CD70, which was a costimulatory molecule, was found to increase on CD4+ T cells during HIV infection. Overexpression of CD70 on CD4+ T cells was recently reported to associate with highly pathogenic proinflammatory Th1/Th17 polarization in multiple sclerosis. Thus, the role of CD70 in the imbalance of Th polarization and immune overactivation during HIV infection needs to be investigated. Here, we found that the elevated frequency of CD70 + CD4+ T cells was negatively correlated with CD4 count and positively associated with immune activation in treatment-naïve people living with HIV (PLWH). More importantly, CD70 expression defined a population of proinflammatory Th1/17/22/GM subsets in PLWH. Blocking CD70 decreased the mRNA expression of subset-specific markers during Th1/17/22/GM polarization. Furthermore, we demonstrated that CD70 influenced the differentiation of these Th cells through STAT pathway. Finally, it was revealed that patients with a high baseline level of CD70 on CD4+ T cells exhibited a greater risk of poor immune reconstitution after antiretroviral therapy (ART) than those with low CD70. In general, our data highlighted the role of CD70 in Th1/17/22/GM differentiation during HIV infection and provided evidence for CD70 as a potential biomarker for predicting immune recovery.

Incomplete immune reconstitution and its predictors in people living with HIV in Wuhan, China.

OBJECTIVE: This study aimed to build and validate a nomogram model to predict the risk of incomplete immune reconstitution in people living with HIV (PLWH). METHODS: Totally 3783 individuals with a confirmed diagnosis of HIV/AIDS were included. A predictive model was developed based on a retrospective set (N = 2678) and was validated using the remaining cases (N = 1105). Univariate and multivariate logistic regression analyses were performed to determine valuable predictors among the collected clinical and laboratory variables. The predictive model is presented in the form of a nomogram, which is internally and externally validated with two independent datasets. The discrimination of nomograms was assessed by calculating the area under the curve (AUC). Besides, calibration curve and decision curve (DCA) analyses were performed in the training and validation sets. RESULTS: The final model comprised 5 predictors, including baseline CD4, age at ART initiation, BMI, HZ and TBIL. The AUC of the nomogram model was 0.902, 0.926, 0.851 in the training cohort, internal validation and external cohorts. The calibration accuracy and diagnostic performance were satisfactory in both the training and validation sets. CONCLUSIONS: This predictive model based on a retrospective study was externally validated using 5 readily available clinical indicators. It showed high performance in predicting the risk of incomplete immune reconstitution in people living with HIV.

[Differences in biochemical indexes and AIDS-related complications at baseline in HIV- infected patients with different levels of immune reconstitution after antiretroviral therapy].

Objective: To observe the differences in biochemical indexes and AIDS-related complications at baseline in HIV-infected patients with different levels of immune reconstitution to antiretroviral therapy (ART). Methods: The subjects were treat-naïve adult HIV-infected patients who were followed up for more than 24 months in the Guangzhou Eighth People's Hospital affiliated infection clinic at Guangzhou Medical University from January 2010 to December 2017. CD4+ T lymphocyte count at baseline at <200, 200-350, and >350 cells/µl levels were divided into poor, partial, and good immune reconstitution groups. The Kruskal-Wallis H and chi-square tests were used to analyze the differences in baseline sociodemographic characteristics, biochemical indexes, and AIDS-related complications among different groups. The SPSS 20.0 software was used for statistical analysis. Results: Among the 3 900 HIV-infected individuals, 385 cases (9.9%), 1 206 cases (30.9%), and 2 309 cases (59.2%) were grouped into poor, partial and good immune reconstitution groups, respectively. The baseline biochemical indexes of leukocyte, platelet, hemoglobin, TG, TC, FPG, AST, ALT and total bilirubin in the poor immune reconstitution group were significantly different from those in the good immune reconstitution group (all P<0.05). The proportion of AIDS-related complications at baseline in the poor immune reconstitution group, such as tuberculosis, pneumocystis yeli pneumonia, disseminated mycosis, esophageal candidiasis, extrapulmonary tuberculosis, dermatitis, oral candidiasis, oral mucous leukoplakia, continuous diarrhea for more than 1 month and continuous or intermittent fever for more than 1 month, was significantly higher than that in the good immune reconstitution group (all P<0.05). Conclusions: The biochemical indexes and AIDS-related complications in HIV-infected patients with different levels of immune reconstitution were significantly different at baseline. Attention should be paid to monitoring abnormal biomedical indicators and AIDS-related complications at baseline.

Immune reconstitution following alemtuzumab therapy is characterized by exhausted T cells, increased regulatory control of proinflammatory T cells and reduced B cell control.

Alemtuzumab is a monoclonal antibody targeting CD52 on the surface of immune cells, approved for the treatment of active relapsing-remitting multiple sclerosis (RRMS). The purpose of this study was to analyze the repopulation of peripheral lymphocytes following alemtuzumab-induced lymphocyte depletion and investigate associations with disease activity and development of secondary autoimmunity. For this, blood samples were collected two years after initiation of alemtuzumab treatment and lymphocytes were subjected to a comprehensive flow cytometry analysis. Included in the study were 40 patients treated with alemtuzumab and 40 treatment-naïve patients with RRMS. Disease activity and development of secondary autoimmune disease was evaluated after three years of treatment. Our study confirms that alemtuzumab treatment profoundly alters the circulating lymphocyte phenotype and describes a reconstituted immune system characterized by T cell activation/exhaustion, an increased regulatory control of IL-17 producing effector T cells and CD20+ T cells, and a reduced control of B cells. There were no obvious associations between immune cell subsets and disease activity or development of secondary autoimmune disease during treatment with alemtuzumab. Our results indicate that the reconstituted immune response is skewed towards a more effective regulatory control of MS-associated proinflammatory T cell responses. Also, the enlarged pool of naïve B cells together with the apparent decrease in control of B cell activity may explain why alemtuzumab-treated patients retain the ability to mount a humoral immune response towards new antigens.

Cryopreservation of mouse thymus depletes thymocytes but supports immune reconstitution on transplantation.

Cryopreservation of mouse thymus depletes donor thymocytes but preserves thymus function when transplanted after thawing into athymic mice. No differences in immune reconstitution were observed between fresh and frozen/thawed transplants suggesting that donor thymocyte depletion does not affect outcome. Thus, cryopreservation of thymus may improve outcomes in thymus transplant patients.