Alexander Shimabukuro-Vornhagen

The role of B cells in the pathogenesis of graft-versus-host disease

Allogeneic hematopoietic stem cell transplantation is an established treatment modality for malignant and nonmalignant hematologic diseases. Acute and chronic graft-versus-host diseases (GVHDs) are a major cause of morbidity and mortality after allogeneic stem cell transplantation. T cells have been identified as key players in the graft-versus-host reaction and, therefore, most established drugs used against GVHD target T cells. Despite our knowledge on the pathogenesis of the GVH reaction, success of established therapies for prevention and treatment of GHVD is unsatisfactory. Recently, animal and human studies demonstrated that B cells are involved in the immunopathophysiology of acute and chronic GVHD. Early phase clinical trials of B-cell depletion with rituximab have shown beneficial effects on both acute and chronic GVHD. This review summarizes the current experimental and clinical evidence for the involvement of B cells in the pathogenesis of acute and chronic GVHD and discusses the clinical implications for the management of patients undergoing allogeneic stem cell transplantation.

Functional activity of natural antibody is altered in Cr2-deficient mice.

The major source of natural IgM Abs are B-1 cells, which differ from conventional B cells in their anatomic location, cell surface phenotype, restricted usage of particular VH genes and limited use of N-region addition during V-D-J rearrangement. The origin of B-1 cells is unclear. However, they are capable of self-renewal and their development is sensitive to signaling via the B cell receptor, as genetic defects that impair the strength of the signal often result in limited development. These findings suggest that B-1 cells require either an intrinsic signal, or contact with Ag, for positive selection and expansion and/or maintenance in the periphery. In support of interaction with cognate Ag, deficiency in the complement receptors CD21/CD35 results in a 30–40% decrease in the CD5+ B-1 population. To determine whether this reduction reflects a loss of certain specificities or simply a proportional decline in the repertoire, we examined peritoneal B cells isolated from Cr2+ and Cr2def mice for recognition of a B-1 cell Ag, i.e., phosphatidylcholine, and assayed for injury in an IgM natural Ab-dependent model of reperfusion injury. We found a similar frequency of phosphatidylcholine-specific CD5+ B-1 cells in the two strains of mice. By contrast, the Cr2def mice have reduced injury in the IgM-dependent model of reperfusion injury. Reconstitution of the deficient mice with pooled IgM or adoptive transfer of Cr2+ peritoneal B cells restored injury. These results suggest that complement receptors CD21/CD35 are important in maintenance of the B-1 cell repertoire to some, but not all, specificities.

Lymphocyte-Rich Classical Hodgkin's Lymphoma: Clinical Presentation and Treatment Outcome in 100 Patients Treated Within German Hodgkin's Study Group Trials

PURPOSE To investigate the clinical characteristics and treatment outcome of patients with lymphocyte-rich classical Hodgkins lymphoma (LRCHL) compared with other histologic subtypes of Hodgkins lymphoma (HL). PATIENTS AND METHODS From a total of 2,715 patients with biopsy-proven HL treated within the trials HD7 to HD12 of the German Hodgkins Study Group, 100 patients (4%) with LRCHL, 145 patients (5%) with lymphocyte-predominant HL (LPHL), 1,688 patients (62%) with nodular sclerosis, 731 patients (27%) with mixed cellularity, and 23 patients (1%) with lymphocyte depletion were identified. Patients with LRCHL had a median age of 38 years (range, 16 to 74 years). RESULTS Compared with other histologic subtypes, patients with LRCHL are, on average, older and usually present with early stages of disease (stage I, 34%; stage II, 46%). The median time of follow-up was 32.2 months (95% CI, 28.2 to 37.0 months). Complete and partial remission was achieved in 96 patients (96%) and four patients (4%), respectively, with LRCHL. The event-free and overall survival rates were 97% (95% CI, 93% [corrected] to 100% [corrected]) and 97% (95% CI, 93% [corrected] to 100% [corrected]), respectively, at 30 months. Only three patients died; all of the deaths were caused by treatment-related toxicities. CONCLUSION LRCHL is a distinct subtype of CHL, with features of CHL and LPHL, and is a rare entity accounting for only 4% of HLs. LRCHL has a different pattern of clinical presentation and age and sex distribution than other CHLs. It is associated with an excellent prognosis if treated with current treatment regimens. When treating patients with LRCHL, great attention should be paid to avoid acute toxicities.

Comparison of bone marrow versus peripheral blood allogeneic hematopoietic stem cell transplantation for hematological malignancies in adults - a systematic review and meta-analysis.

It is still under debate whether bone marrow (BM) or peripheral blood (PB) should be the preferred stem cell source in adult patients undergoing allogeneic stem cell transplantation for hematological malignancies. After systematic literature search we identified nine randomised controlled trials comparing BM and PB as stem cell source from 2341 total hits. Meta-analysis involving 1521 patients showed a statistically significant reduction in overall and extensive chronic GvHD for patients transplanted with BM (HR 0.72; 95% CI 0.61 to 0.85 and HR 0.69; 95% CI 0.54 to 0.9), but no difference in overall and disease-free survival. In the related donor setting, data from two of eight studies demonstrated a significant increase of relapse incidence for BM (HR 2.73; 95% CI 1.47 to 5.08). This systematic review demonstrates that the current clinical standard to use peripheral blood stem cells instead of bone marrow for allo-SCT is not inferior with regard to the primary outcome overall survival.

CD40-activated B cells can be generated in high number and purity in cancer patients: analysis of immunogenicity and homing potential

Cellular adjuvants such as dendritic cells (DC) are in the focus of tumour immunotherapy. In DC‐vaccine trials, induction of tumour antigen‐specific immunity is observed frequently and well‐documented clinical responses have been reported. However, the overall response rate is less than 3%, therefore alternative strategies are being investigated. CD40‐activated B cells (CD40‐B) have been characterized previously as an interesting alternative because they present antigen efficiently and can be expanded by several logs from small amounts of peripheral blood. To determine the central technical challenges of cell‐based vaccines we performed a single‐patient analysis of 502 patients from DC‐based tumour vaccine trials and identified at least three factors contributing to their limited efficiency: (1) lack of cell numbers; (2) lack of documented purity thus high contamination of bystander cells; and (3) lack of quality control and thus heterogeneous or unknown expression of important surface molecules such as major histocompatibility complex (MHC) and chemokine receptors. Based on these findings we re‐evaluated the CD40‐B approach in cancer patients. Here, we show that proliferation of B cells from cancer patients is equivalent to that observed in healthy donors. Purity is always > 90% after 2 weeks and remains stable for several weeks. They have comparable antigen‐presenting capability determined phenotypically and by allogeneic mixed lymphocyte reaction. Expression of CCR7 and CD62L was detected in all samples and B cells migrated towards the relevant homing chemokines. Taken together, CD40‐B cells from cancer patients can be expanded in virtually unlimited numbers at high purity and full function concerning antigen‐presentation and migratory properties.

Activated human B cells: stimulatory or tolerogenic antigen-presenting cells?

To the editor: In recent years the antibody-independent functions of B cells have gained increasing attention. B cells can become potent antigen-presenting cells (APCs) after activation. Contrary to activated B cells, resting B cells can act as immunoregulatory cells. Two interesting recent papers

Anti-thymocyte globulins for post-transplant graft-versus-host disease prophylaxis—A systematic review and meta-analysis

BACKGROUND Despite advances made in allogeneic hematopoietic stem cell transplantation (alloSCT), graft versus host disease (GvHD) remains a major problem. The main strategy to combat GvHD is prophylaxis and ATG plays a major role in this arena. Conflicting reports on the effectiveness of ATG on GvHD prevention prompted us to address this question by means of a systematic review and meta-analysis. METHODS Six prospective randomized controlled trials (RCT) comparing the addition of ATG to standard immunosuppressive regimen as GvHD prophylaxis were analyzed. All ATG preparations were considered but homogeneity in type of preparation and dosage had to be observed within each trial. RESULTS Our meta-analysis reveals that the incidence of grade II-IV GvHD was significantly lower in patients receiving ATG. Addition of ATG had no impact on overall survival, relapse or non-relapse mortality. CONCLUSIONS Based on the current level of the data analyzed in this systematic review, we cannot conclude a general recommendation for the use of ATG for GvHD prophylaxis in alloSCT. In patients who are at high risk for severe GvHD it should be considered individually. However, due to the heterogeneity of the analyzable studies it seems likely that future studies might change the results of the pooled data of this meta-analysis. In order to improve the current level of data, further randomized studies in this topic are therefore urgently warranted.

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Generation of Human CD40-activated B cells

CD40-activated B cells (CD40-B cells) have been identified as an alternative source of immuno-stimulatory antigen-presenting cells (APC) for cancer immunotherapy. Compared to Dendritic cells (DCs), the best characterized APC, CD40-B cells have several distinct biological and technical properties. Similar to DCs, B cells show an increased expression of MHC and co-stimulatory molecules (Fig.1b), exhibit a strong migratory capacity and present antigen presentation efficiently to T cells, after stimulation with interleukin-4 and CD40 ligand (CD40L). However, in contrast to immature or mature DCs, CD40-B cells express the full lymph node homing triad consisting of CD62L, CCR7/CXCR4, and leukocyte function antigen-1 (LFA1, CD11a/CD18), necessary for homing to secondary lymphoid organs (Fig.1a). CD40-B cells can be generated without difficulties from very small amounts of peripheral blood which can be further expanded in vitro to very large amounts of highly-pure CD40-B cells (>10(9) cells per patient) from healthy donors as well as cancer patients (Fig.1c,d). In this protocol we demonstrate how to obtain fully activated CD40-B cells from human PBMC. Key molecules for the cell culture are CD40 ligand, interleukin-4 (IL-4) and cyclosporin A (CsA), which are replenished in a 3-4 day culture cycle. For laboratory purposes CD40-stimulation is provided by NIH/3T3 cells expressing recombinant human CD40 ligand (tCD40L NIH/3T3). To avoid contamination with non-transfected cells, expression of the human CD40 ligand on the transfectants has to be checked regularly (Fig.2). After 14 days CD40-B cell cultures consist of more than 95% pure B cells and an expansion of CD40-B cells over 65 days is frequently possible without any loss of function. CD40-B cells efficiently take up, process and present antigens to T cells. They do not only prime naïve, but also expand memory T cells. CD40-activated B cells can be used to study B-cell activation, differentiation and function. Moreover, they represent a promising tool for therapeutic or preventive vaccination against tumors.

Statins inhibit human APC function: implications for the treatment of GVHD

To the editor: Recently Zeiser et al reported the results of their study on the effects of atorvastatin on acute graft-versus-host disease (aGVHD) and graft-versus-leukemia (GVL) activity.[1][1] Using murine models of aGVHD they showed that treatment with atorvastatin of both the donor and the