CD4 memory T cells survive and proliferate but fail to differentiate in the absence of CD40

Secondary T cell responses are enhanced because of an expansion in numbers of antigen-specific (memory) cells. Using major histocompatibility complex class II tetramers we have tracked peptide-specific endogenous (non–T cell receptor transgenic) CD4 memory T cells in normal and in costimulation-deficient mice. CD4 memory T cells were detectable after immunization for more than 200 days, although decay was apparent. Memory cells generated in CD40 knockout mice by immunization with peptide-pulsed wild-type dendritic cells survived in the absence of CD40 and proliferated when boosted with peptide (plus adjuvant) in a CD40-independent fashion. However, differentiation of the memory cells into cytokine-producing effector cells did not occur in the absence of CD40. The data indicate that memory cells can be generated without passing through the effector cell stage

Lymphoma-associated mutations in autoreactive memory B cells of patients with Sjögren's syndrome

We recently demonstrated that normal memory B lymphocytes carry a substantial number of de novo mutations in the genome. Here, we performed exome-wide somatic mutation analyses of bona fide autoreactive rheumatoid factor (RF)-expressing memory B cells retrieved from patients with Sjӧgren's syndrome (SS). The amount and repertoire of the de novo exome mutations of RF B cells were found to be essentially different from those detected in healthy donor memory B cells. In contrast to the mutation spectra of normal B cells, which appeared random and non-selected, the mutations of the RF B cells were greater in number and enriched for mutations in genes also found mutated in B-cell non-Hodgkin lymphomas. During the study, one of the SS patients developed a diffuse large B-cell lymphoma (DLBCL) out of an RF clone that was identified 2 years earlier in an inflamed salivary gland biopsy. The successive oncogenic events in the RF precursor clone and the DLBCL were assessed. In conclusion, our findings of enhanced and selected genomic damage in growth-regulating genes in RF memory B cells of SS patients together with the documented transformation of an RF-precursor clone into DLBCL provide unique novel insight into the earliest stages of B-cell derailment and lymphomagenesis.</p

Lymphoma-associated mutations in autoreactive memory B cells of patients with Sjögren's syndrome

We recently demonstrated that normal memory B lymphocytes carry a substantial number of de novo mutations in the genome. Here, we performed exome-wide somatic mutation analyses of bona fide autoreactive rheumatoid factor (RF)-expressing memory B cells retrieved from patients with Sjӧgren's syndrome (SS). The amount and repertoire of the de novo exome mutations of RF B cells were found to be essentially different from those detected in healthy donor memory B cells. In contrast to the mutation spectra of normal B cells, which appeared random and non-selected, the mutations of the RF B cells were greater in number and enriched for mutations in genes also found mutated in B-cell non-Hodgkin lymphomas. During the study, one of the SS patients developed a diffuse large B-cell lymphoma (DLBCL) out of an RF clone that was identified 2 years earlier in an inflamed salivary gland biopsy. The successive oncogenic events in the RF precursor clone and the DLBCL were assessed. In conclusion, our findings of enhanced and selected genomic damage in growth-regulating genes in RF memory B cells of SS patients together with the documented transformation of an RF-precursor clone into DLBCL provide unique novel insight into the earliest stages of B-cell derailment and lymphomagenesis.</p

Establishment of Systems to Enable Isolation of Porcine Monoclonal Antibodies Broadly Neutralizing the Porcine Reproductive and Respiratory Syndrome Virus

The rapid evolution of porcine reproductive and respiratory syndrome viruses (PRRSV) poses a major challenge to effective disease control since available vaccines show variable efficacy against divergent strains. Knowledge of the antigenic targets of virus-neutralizing antibodies that confer protection against heterologous PRRSV strains would be a catalyst for the development of next-generation vaccines. Key to discovering these epitopes is the isolation of neutralizing monoclonal antibodies (mAbs) from immune pigs. To address this need, we sought to establish systems to enable the isolation of PRRSV neutralizing porcine mAbs. We experimentally produced a cohort of immune pigs by sequential challenge infection with four heterologous PRRSV strains spanning PRRSV-1 subtypes and PRRSV species. Whilst priming with PRRSV-1 subtype 1 did not confer full protection against a subsequent infection with a PRRSV-1 subtype 3 strain, animals were protected against a subsequent PRRSV-2 infection. The infection protocol resulted in high serum neutralizing antibody titers against PRRSV-1 Olot/91 and significant neutralization of heterologous PRRSV-1/-2 strains. Enriched memory B cells isolated at the termination of the study were genetically programmed by transduction with a retroviral vector expressing the Bcl-6 transcription factor and the anti-apoptotic Bcl-xL protein, a technology we demonstrated efficiently converts porcine memory B cells into proliferating antibody-secreting cells. Pools of transduced memory B cells were cultured and supernatants containing PRRSV-specific antibodies identified by flow cytometric staining of infected MARC-145 cells and in vitro neutralization of PRRSV-1. Collectively, these data suggest that this experimental system may be further exploited to produce a panel of PRRSV-specific mAbs, which will contribute both to our understanding of the antibody response to PRRSV and allow epitopes to be resolved that may ultimately guide the design of immunogens to induce cross-protective immunity

Stable long-term cultures of self-renewing B cells and their applications

Monoclonal antibodies are essential therapeutics and diagnostics in a large number of diseases. Moreover, they are essential tools in all sectors of life sciences. Although the great majority of monoclonal antibodies currently in use are of mouse origin, the use of human B cells to generate monoclonal antibodies is increasing as new techniques to tap the human B cell repertoire are rapidly emerging. Cloned lines of immortalized human B cells are ideal sources of monoclonal antibodies. In this review, we summarize our studies to the regulation of the replicative life span, differentiation, and maturation of B cells that led to the development of a platform that uses immortalization of human B cells by in vitro genetic modification for antibody development. We describe a number of human antibodies that were isolated using this platform and the application of the technique in other species. We also discuss the use of immortalized B cells as antigen-presenting cells for the discovery of tumor neoantigen

Differential role of CD97 in interleukin-8-induced and granulocyte-colony stimulating factor-induced hematopoietic stem and progenitor cell mobilization

CD97 is broadly expressed on hematopoietic cells and is involved in neutrophil migration. Since neutrophils are key regulators in HSC/HPC mobilization, we studied a possible role for CD97 in interleukin-8 and granulocyte-colony stimulating factor-induced HSC/HPC mobilization. Mobilization was absent in mice receiving CD97 mAb followed by interleukin-8, while granulocyte-colony stimulating factor-induced mobilization remained unaltered following anti-CD97 administration. Furthermore, combined administration of CD97 mAb and IL-8 induced a significant reduction in the neutrophilic compartment. We hypothesize that the absence of interleukin-8-induced HSC/HPC mobilization after CD97 mAb administration is due to its effect on neutrophil functio