Human FcγRIIIa activation on splenic macrophages drives dengue pathogenesis in mice.

Although dengue virus (DENV) infection typically causes asymptomatic disease, DENV-infected patients can experience severe complications. A risk factor for symptomatic disease is pre-existing anti-DENV IgG antibodies. Cellular assays suggested that these antibodies can enhance viral infection of Fcγ receptor (FcγR)-expressing myeloid cells.

Mechanism of glycoform specificity and in vivo protection by an anti-afucosylated IgG nanobody.

Immunoglobulin G (IgG) antibodies contain a complex N-glycan embedded in the hydrophobic pocket between its heavy chain protomers. This glycan contributes to the structural organization of the Fc domain and determines its specificity for Fcγ receptors, thereby dictating distinct cellular responses. The variable construction of this glycan structure leads to highly-related, but non-equivalent glycoproteins known as glycoforms.

Synthetic nanobodies as tools to distinguish IgG Fc glycoforms.

Protein glycosylation is a crucial mediator of biological functions and is tightly regulated in health and disease. However, interrogating complex protein glycoforms is challenging, as current lectin tools are limited by cross-reactivity while mass spectrometry typically requires biochemical purification and isolation of the target protein. Here, we describe a method to identify and characterize a class of nanobodies that can distinguish glycoforms without reactivity to off-target glycoproteins or glycans.

Fc-engineered antibody therapeutics with improved anti-SARS-CoV-2 efficacy.

Monoclonal antibodies with neutralizing activity against SARS-CoV-2 have demonstrated clinical benefits in cases of mild-to-moderate SARS-CoV-2 infection, substantially reducing the risk for hospitalization and severe disease. Treatment generally requires the administration of high doses of these monoclonal antibodies and has limited efficacy in preventing disease complications or mortality among hospitalized patients with COVID-19. Here we report the development and evaluation of anti-SARS-CoV-2 monoclonal antibodies with optimized Fc domains that show superior potency for prevention or treatment of COVID-19.

Fc-engineered antibody therapeutics with improved efficacy against COVID-19.

Monoclonal antibodies (mAbs) with neutralizing activity against SARS-CoV-2 have demonstrated clinical benefit in cases of mild to moderate SARS-CoV-2 infection, substantially reducing the risk for hospitalization and severe disease1-4. Treatment generally requires the administration of high doses of these mAbs with limited efficacy in preventing disease complications or mortality among hospitalized COVID-19 patients5. Here we report the development and evaluation of Fc-optimized anti-SARS-CoV-2 mAbs with superior potency to prevent or treat COVID-19 disease.

Hoxb5 defines the heterogeneity of self-renewal capacity in the hematopoietic stem cell compartment.

Self-renewal and multipotency are essential functions of hematopoietic stem cells (HSCs). To maintain homeostatic hematopoiesis, functionally uniform HSCs have been thought to be an ideal cell-of-origin. Recent technological advances in the field have allowed us to analyze HSCs with single cell resolution and implicate that functional heterogeneity may exist even within the highly purified HSC compartment.

Neutrophil and monocyte kinetics play critical roles in mouse peritoneal adhesion formation.

Peritoneal adhesions are pathological fibroses that ensnare organs after abdominal surgery. This dense connective tissue can cause small bowel obstruction, female infertility, and chronic abdominal pain. The pathogenesis of adhesions is a fibrotic response to tissue damage coordinated between mesothelial cells, fibroblasts, and immune cells.

The GABA receptor GABRR1 is expressed on and functional in hematopoietic stem cells and megakaryocyte progenitors.

GABRR1 is a rho subunit receptor of GABA, the major inhibitory neurotransmitter in the mammalian brain. While most investigations of its function focused on the nervous system, its regulatory role in hematopoiesis has not been reported. In this study, we found GABRR1 is mainly expressed on subsets of human and mouse hematopoietic stem cells (HSCs) and megakaryocyte progenitors (MkPs).

Antibody Conditioning Enables MHC-Mismatched Hematopoietic Stem Cell Transplants and Organ Graft Tolerance.

Hematopoietic cell transplantation can correct hematological and immunological disorders by replacing a diseased blood system with a healthy one, but this currently requires depleting a patient's existing hematopoietic system with toxic and non-specific chemotherapy, radiation, or both. Here we report an antibody-based conditioning protocol with reduced toxicity and enhanced specificity for robust hematopoietic stem cell (HSC) transplantation and engraftment in recipient mice. Host pre-treatment with six monoclonal antibodies targeting CD47, T cells, NK cells, and HSCs followed by donor HSC transplantation enabled stable hematopoietic system reconstitution in recipients with mismatches at half (haploidentical) or all major histocompatibility complex (MHC) genes.

Programmed cell removal by calreticulin in tissue homeostasis and cancer.

Macrophage-mediated programmed cell removal (PrCR) is a process essential for the clearance of unwanted (damaged, dysfunctional, aged, or harmful) cells. The detection and recognition of appropriate target cells by macrophages is a critical step for successful PrCR, but its molecular mechanisms have not been delineated. Here using the models of tissue turnover, cancer immunosurveillance, and hematopoietic stem cells, we show that unwanted cells such as aging neutrophils and living cancer cells are susceptible to "labeling" by secreted calreticulin (CRT) from macrophages, enabling their clearance through PrCR.

Where Hematopoietic Stem Cells Live: The Bone Marrow Niche.

Hematopoietic stem cells (HSCs) can sustain the production of blood throughout one's lifetime. However, for proper self-renewal of its own population and differentiation to blood, the HSC requires a specialized microenvironment called the "niche." Recent Advances: Recent studies using novel mouse models have shed new light on the cellular architecture and function of the HSC niche.

Normal and Neoplastic Stem Cells.

A stem cell is broadly defined as a cell that retains the capacity to self-renew, a feature that confers the ability to continuously make identical daughter cells or additional cells that will differentiate into downstream progeny. This highly regulated genetic program to retain "stemness" is under active investigation. Research in our laboratory has explored similarities and differences in embryonic, tissue-specific, and neoplastic stem cells and their terminally differentiated counterparts.

Hoxb5 marks long-term haematopoietic stem cells and reveals a homogenous perivascular niche.

Haematopoietic stem cells (HSCs) are arguably the most extensively characterized tissue stem cells. Since the identification of HSCs by prospective isolation, complex multi-parameter flow cytometric isolation of phenotypic subsets has facilitated studies on many aspects of HSC biology, including self-renewal, differentiation, ageing, niche, and diversity. Here we demonstrate by unbiased multi-step screening, identification of a single gene, homeobox B5 (Hoxb5, also known as Hox-2.