Kindlin-3 maintains marginal zone B cells but confines follicular B cell activation and differentiation

Integrin-mediated interactions between hematopoietic cells and their microenvironment are important for the development and function of immune cells. Here, the role of the integrin adaptor Kindlin-3 in B cell homeostasis is studied. Comparing the individual steps of B cell development in B cell-specific Kindlin-3 or alpha4 integrin knockout mice, we found in both conditions a phenotype of reduced late immature, mature, and recirculating B cells in the bone marrow. In the spleen, constitutive B cell-specific Kindlin-3 knockout caused a loss of marginal zone B cells and an unexpected expansion of follicular B cells. Alpha4 integrin deficiency did not induce this phenotype. In Kindlin-3 knockout B cells VLA-4 as well as LFA-1-mediated adhesion was abrogated, and short-term homing of these cells in vivo was redirected to the spleen. Upon inducible Kindlin-3 knockout, marginal zone B cells were lost due to defective retention within 2 weeks, while follicular B cell numbers were unaltered. Kindlin-3 deficient follicular B cells displayed higher IgD, CD40, CD44, CXCR5, and EBI2 levels, and elevated PI3K signaling upon CXCR5 stimulation. They also showed transcriptional signatures of spontaneous follicular B cell activation. This activation manifested in scattered germinal centers in situ, early plasmablasts differentiation, and signs of IgG class switch.

CD1d expression on chronic lymphocytic leukemia B cells affects disease progression and induces T cell skewing in CD8 positive and CD4CD8 double negative T cells

Chronic lymphocytic leukemia develops within a complex network driven by genetic mutations and microenvironmental interactions. Among the latter a complex interplay with the immune system is established by the clone. Next to a proposed recruitment of support from T and myeloid cells, potential anti-CLL immune reactions need to be subverted. By using TCL1 mice as a CLL model, we show that TCR-Vβ7+ NK1.1+ T cells are overrepresented in this disease model and constitute a main subset of peripheral CD3+ cells with biased TCR usage, showing that these cells account for a major part for T cell skewing in TCL1 mice. Moreover, we show that overrepresentation is dependent on CD1d expression in TCL1 mice, implicating that these cells belong to a NKT-like cell fraction which are restricted to antigen presented by the MHC-like surface marker CD1d. Accordingly, we observed a high fraction of CD161+ cells within overrepresented T cells in CLL patients and we found downregulation of CD1d on the surface of CLL cells, both in TCL1 mice and patients. Finally, we show that in TCL1 mice, CD1d deficiency resulted in shortened overall survival. Our results point to an interaction between CLL and CD161+ T cells that may represent a novel therapeutic target for immune modulation.

ILK Induction in Lymphoid Organs by a TNFα-NF-κB-Regulated Pathway Promotes the Development of Chronic Lymphocytic Leukemia

The proliferation of chronic lymphocytic leukemia (CLL) cells requires communication with the lymphoid organ microenvironment. Integrin-linked kinase (ILK) is a multifunctional intracellular adaptor protein that transmits extracellular signals to regulate malignant cell motility, metastasis, and cell-cycle progression, but is poorly characterized in hematologic malignancies. In this study, we investigated the role of ILK in the context of CLL and observed high ILK expression in patient samples, particularly in tumor cells harboring prognostic high-risk markers such as unmutated IGHV genes, high Zap70, or CD38 expression, or a signature of recent proliferation. We also found increased numbers of Ki67 (MKI67)-positive cells in regions of enhanced ILK expression in lymph nodes from CLL patients. Using coculture conditions mimicking the proliferative lymph node microenvironment, we detected a parallel induction of ILK and cyclin D1 (CCND1) expression in CLL cells that was dependent on the activation of NF-κB signaling by soluble TNFα. The newly synthesized ILK protein colocalized to centrosomal structures and was required for correct centrosome clustering and mitotic spindle organization. Furthermore, we established a mouse model of CLL in which B-cell-specific genetic ablation of ILK resulted in decelerated leukemia development due to reduced organ infiltration and proliferation of CLL cells. Collectively, our findings describe a TNFα-NF-κB-mediated mechanism by which ILK expression is induced in the lymph node microenvironment and propose that ILK promotes leukemogenesis by enabling CLL cells to cope with centrosomal defects acquired during malignant transformation. Cancer Res; 76(8); 2186-96. ©2016 AACR.

Differential bone marrow homing capacity of VLA-4 and CD38 high expressing chronic lymphocytic leukemia cells

Background

VLA-4 and CD38 predict a poor clinical outcome in chronic lymphocytic leukemia (CLL). We used CLL samples with discordant VLA-4/CD38 risk to address their individual roles in human bone marrow infiltration (BM), CLL cell homing to murine BM, and in supportive CLL cell-stromal cell interactions.

Methods

VLA-4, CD38, and Ki-67 expression was measured in CLL cells from peripheral blood (PB) and bone marrow (BM) aspirates. CLL BM infiltration rates, routinely determined by Pathology, were correlated to VLA-4 and CD38 expression. Short-term homing capacity of CLL cells was evaluated by adoptive transfer experiments. CLL cell viability and adhesion in stromal cell co-culture was determined.

Results

About 20% of CLL samples in our cohort displayed discordant VLA-4 and CD38 risk, with either high VLA-4 and low CD38 risk or vice versa. Using particularly such samples, we observed that VLA-4, and not CD38, was responsible for recirculation of CLL cells to murine BM. Human BM infiltration was also significantly higher in patients with high VLA-4 risk but not high CD38 risk. However, both molecules acted as independent prognostic markers. While both VLA-4 and CD38 expression were increased in BM-derived CLL cells, and VLA-4+ and CD38+ subpopulations showed enriched Ki-67 expression, VLA-4 did not contribute to CLL cell protection by stromal cells in vitro.

Conclusions

Our data argue for a prominent role of VLA-4 but not CD38 expression in the homing of CLL cells to BM niches and in human BM infiltration,but only a limited role in their protection by stromal cells.

Development of CLL in the TCL1 transgenic mouse model is associated with severe skewing of the T-cell compartment homologous to human CLL

Chronic lymphocytic leukemia (CLL) cells require complex microenvironmental and immunologic interactions to survive and proliferate. Such interactions might be best recreated in animal models; however, this needs extensive verification. We therefore investigated the composition of the T-cell compartment in the Eμ-TCL1 transgenic mouse, currently the most widely used murine model for CLL. Immunophenotyping and transplant approaches were used to define T-cell subsets at various stages of CLL. Analogous to human CLL, we observed a skewing of T-cell subsets from naive to antigen-experienced memory T cells that was more pronounced in lymph nodes than in blood. Transplantation of CLL into non-transgenic recipients was feasible without immunosuppression in a pure C57BL/6 background and resulted in the prominent skewing of the T cells of the recipient mice. Both in spontaneously developed CLL and in the transplantation setting, a loss in T-cell receptor diversity was observed, with a relevant number of clonal T-cell populations arising. This suggests that antigen-dependent differentiation toward the T memory pool is initiated by murine CLL cells. In summary, we validate the TCL1 transgenic mouse model for analysis of T-cell phenotypes and suggest a CLL-dependent antigen-driven skewing of T cells in these mice.

The spectrum of fungal allergy

Fungi can be found throughout the world. They may live as saprophytes, parasites or symbionts of animals and plants in indoor as well as outdoor environment. For decades, fungi belonging to the ascomycota as well as to the basidiomycota have been known to cause a broad panel of human disorders. In contrast to pollen, fungal spores and/or mycelial cells may not only cause type I allergy, the most prevalent disease caused by molds, but also a large number of other illnesses, including allergic bronchopulmonary mycoses, allergic sinusitis, hypersensitivity pneumonitis and atopic dermatitis; and, again in contrast to pollen-derived allergies, fungal allergies are frequently linked with allergic asthma. Sensitization to molds has been reported in up to 80% of asthmatic patients. Although research on fungal allergies dates back to the 19th century, major improvements in the diagnosis and therapy of mold allergy have been hampered by the fact that fungal extracts are highly variable in their protein composition due to strain variabilities, batch-to-batch variations, and by the fact that extracts may be prepared from spores and/or mycelial cells. Nonetheless, about 150 individual fungal allergens from approximately 80 mold genera have been identified in the last 20 years. First clinical studies with recombinant mold allergens have demonstrated their potency in clinical diagnosis. This review aims to give an overview of the biology of molds and diseases caused by molds in humans, as well as a detailed summary of the latest results on recombinant fungal allergens.

Alternaria alternata NADP-dependent mannitol dehydrogenase is an important fungal allergen

BACKGROUND

Alternaria alternata is one of the most important allergenic fungi worldwide. Mannitol dehydrogenase (MtDH) has previously been shown to be a major allergen of Cladosporium herbarum and cross-reactivity has been demonstrated for several fungal allergens.

OBJECTIVE

The present study's objective was to clone the MtDH from an A. alternata cDNA library, express and purify the recombinant non-fusion protein and test its IgE-binding properties. Methods A cDNA library prepared from A. alternata hyphae and spores was screened for mannitol dehydrogenase by DNA hybridization with the radioactively labelled C. herbarum homologue as a probe. The resulting clone was sequenced and heterologously expressed in Escherichia coli as a recombinant non-fusion protein, which was purified to homogeneity and analysed for its IgE-binding capacity.

RESULTS

The coding sequence of the full-length cDNA clone comprises 798 bp encoding a protein with a molecular mass of 28.6 kDa and a predicted pI of 5.88. Protein sequence analysis revealed an identity of 75% and a homology of 86% between the MtDHs of A. alternata and C. herbarum. The functional mannitol dehydrogenase was expressed in the E. coli strain BL21(DE3) transformed with the vector pMW172 and purified to homogeneity. The enzyme catalyses the NADPH-dependent conversion of d-fructose to d-mannitol. In IgE-ELISA and immunoblots, MtDH is recognized by 41% of A. alternata-allergic patients. In vivo immunoreactivity of the recombinant MtDH was verified by skin prick testing. Finally, inhibition-ELISA experiments confirmed cross-reactivity between the MtDHs of A. alternata and C. herbarum.

CONCLUSION

Mannitol dehydrogenase (Alt a 8) represents an important new allergen of the ascomycete A. alternata that might be suitable for improving diagnostic and therapeutic procedures.

NADP-dependent mannitol dehydrogenase, a major allergen of Cladosporium herbarum

Cladosporium herbarum is an important allergenic fungal species that has been reported to cause allergic diseases in nearly all climatic zones. 5-30% of the allergic population displays IgE antibodies against molds. Sensitization to Cladosporium has often been associated with severe asthma and less frequently with chronic urticaria and atopic eczema. However, no dominant major allergen of this species has been found so far. We present cloning, production, and characterization of NADP-dependent mannitol dehydrogenase of C. herbarum (Cla h 8) and show that this protein is a major allergen that is recognized by IgE antibodies of approximately 57% of all Cladosporium allergic patients. This is the highest percentage of patients reacting with any Cladosporium allergen characterized so far. Cla h 8 was purified to homogeneity by standard chromatographic methods, and both N-terminal and internal amino acid sequences of protein fragments were determined. Enzymatic analysis of the purified natural protein revealed that this allergen represents a NADP-dependent mannitol dehydrogenase that interconverts mannitol and d-fructose. It is a soluble, non-glycosylated cytoplasmic protein. Two-dimensional protein analysis indicated that mannitol dehydrogenase is present as a single isoform. The cDNA encoding Cla h 8 was cloned from a lambda-ZAP library constructed from hyphae and spores. The recombinant non-fusion protein was expressed in Escherichia coli and purified to homogeneity. Its immunological and biochemical identity with the natural protein was shown by enzyme activity tests, CD spectroscopy, IgE immunoblots with sera of patients, and by skin prick testing of Cladosporium allergic patients. This protein therefore is a new major allergen of C. herbarum.