Fluorescence-activated Cell Sorting for Purification of Plasmacytoid Dendritic Cells from the Mouse Bone Marrow

Fluorescence-activated cell sorting (FACS) is a technique to purify specific cell populations based on phenotypes detected by flow cytometry. This method ...

Measuring Endoreduplication by Flow Cytometry of Isolated Tuber Protoplasts

Endoreduplication, the replication of a cell's nuclear genome without subsequent cytokinesis, yields cells with increased DNA content and is associated ...

Virginia Polytechnic Institute and State University

Virginia Tech

It is generally believed that the production of influenza-specific IgG in response to viral infection is dependent on CD4 T cells. However, we previously observed that CD40-deficient mice generate influenza-specific IgG during a primary infection, suggesting that influenza infection may elicit IgG responses independently of CD4 T cell help. In the present study, we tested this hypothesis and show that mice lacking CD40 or CD4 T cells produce detectable titers of influenza-specific IgG and recover from influenza infection in a manner similar to that of normal mice. In contrast, mice completely lacking B cells succumb to influenza infection, despite the presence of large numbers of functional influenza-specific CD8 effector cells in the lungs. Consistent with the characteristics of a T-independent Ab response, long-lived influenza-specific plasma cells are not found in the bone marrow of CD40-/- and class II-/- mice, and influenza-specific IgG titers wane within 60 days postinfection. However, despite the short-lived IgG response, CD40-/- and class II-/- mice are completely protected from challenge infection with the same virus administered within 30 days. This protection is mediated primarily by B cells and Ab, as influenza-immune CD40-/- and class II-/- mice were still resistant to challenge infection when T cells were depleted. These data demonstrate that T cell-independent influenza-specific Ab promotes the resolution of primary influenza infection and helps to prevent reinfection.

CD4 T cell-independent antibody response promotes resolution of primary influenza infection and helps to prevent reinfection.

Cross-linking of CD38 on hematopoietic cells induces activation, proliferation and differentiation of mature T and B cells and mediates apoptosis of myeloid and lymphoid progenitor cells. In addition to acting as a signaling receptor, CD38 is also an enzyme capable of producing several calcium-mobilizing metabolites, including cyclic adenosine diphosphate ribose (cADPR). It has been previously postulated that the calcium-mobilizing metabolites produced by CD38 may regulate its receptor-based activities. To test this hypothesis, we examined whether the enzyme activity of CD38 controls the apoptosis of an anti-CD38-stimulated leukemic B cell. We show that anti-CD38-induced apoptosis of Ba/F3 cells, a murine pro-B cell line, is not affected by blocking the calcium-mobilizing activity of cADPR or by inhibiting intracellular or extracellular calcium mobilization. In addition, we demonstrate that blocking CD38 enzyme activity with 2'-deoxy-2'-fluoro-nicotinamide arabinoside adenine dinucleotide has no effect on apoptosis and that Ba/F3 cells expressing catalytically inactive mutant forms of CD38 still undergo apoptosis upon CD38 cross-linking. Instead, we find that anti-CD38-induced apoptosis is dependent on tyrosine kinase and caspase activation, and that this process appears to be potentiated by the presence of membrane microdomains. Thus, the receptor-mediated functions of CD38 can be separated from its enzyme activity in a murine leukemic cell line, suggesting that CD38 plays multiple, but independent, biologic roles.

CD38 induces apoptosis of a murine pro-B leukemic cell line by a tyrosine kinase-dependent but ADP-ribosyl cyclase- and NAD glycohydrolase-independent mechanism.

Immunity to the intestinal parasite Heligomosomoides polygyrus is dependent on the successful generation of T helper 2 (Th2) memory cells. We showed that B cells contribute to immunity against H. polygyrus by producing antibody (Ab) and by promoting expansion and differentiation of primary and memory Th2 cells. We also demonstrated that cytokine-producing effector B cells were essential for effective immunity to H. polygyrus. Tumor necrosis factor alpha production by B cells was necessary for sustained Ab production, whereas interleukin 2 production by B cells was necessary for Th2 cell expansion and differentiation. These results show that B cells mediate protection from pathogens not only by presenting antigen and secreting antibody but also by producing cytokines that regulate the quality and magnitude of humoral and cellular immune responses.

Cytokine-producing effector B cells regulate type 2 immunity to H. polygyrus.

Brucella spp. are Gram-negative, coccobacillary, facultative intracellular pathogens. B. abortus strain 2308 is a pathogenic strain affecting cattle and humans. Rough B. abortus strain RB51, which lacks the O-side chain of lipopolysaccharide (LPS), is the live attenuated USDA approved vaccine for cattle in the United States. Strain RB51SOD, which overexpresses Cu-Zn superoxide dismutase (SOD), has been shown to confer better protection than strain RB51 in a murine model. Protection against brucellosis is mediated by a strong CD4+ Th(1) and CD8+ Tc(1) adaptive immune response. In order to stimulate a robust adaptive response, a solid innate immune response, including that mediated by dendritic cells, is essential. As dendritic cells (DCs) are highly susceptible to Brucella infection, it is possible that pathogenic strains could limit the innate and thereby adaptive immune response. By contrast, vaccine strains could limit or bolster the innate and subsequent adaptive immune response. Identifying how Brucella vaccines stimulate innate and adaptive immunity is critical for enhancing vaccine efficacy. The ability of rough vaccine strains RB51 and RB51SOD to stimulate DC function has not been characterized. We report that live rough vaccine strain RB51 induced significantly better (p ≤ 0.05) DC maturation and function compared to either strain RB51SOD or smooth virulent strain 2308, based on costimulatory marker expression and cytokine production.

Live Brucella abortus rough vaccine strain RB51 stimulates enhanced innate immune response in vitro compared to rough vaccine strain RB51SOD and virulent smooth strain 2308 in murine bone marrow-derived dendritic cells.

Brucellosis is worldwide zoonoses affecting 500,000 people annually with no approved human vaccines available. Live attenuated Brucella abortus vaccine strain RB51 protects cattle through CD4 and CD8 T-cell mediated responses. However, limited information is known regarding how Brucella stimulate innate immunity. Although the most critical toll like receptors (TLRs) involved in the recognition of Brucella are TLR2, TLR4 and TLR9, it is important to identify the essential TLRs that induce DC activation/function in response to Brucella, to be able to upregulate both vaccine strain RB51-mediated protection, and clearance of pathogenic strain 2308. Furthermore, in spite of the importance of aerosol transmission of Brucella, no published studies have addressed the role of TLRs in the clearance of strain 2308 or strain RB51 from intranasally infected mice. Therefore, we used a (a) bone marrow derived dendritic cell model in TLRKO and control mice to assess the differential role of pathogenic and vaccine strains to induce DC activation and function in vitro, and (b) respiratory model in TLRKO and control mice to assess the critical roles for TLRs in clearance of strains in vivo. In support of the essential TLRs in clearance and protection, we performed challenge experiments to identify if these critical TLRs (as agonists) could enhance vaccine induced protection against pathogenic strain 2308 in a respiratory model. We determined: vaccine strain RB51 induced significant (p≤0.05) DC activation vs. strain 2308 which was not dependent on a specific TLR; strain RB51 induced TNF-α production was TLR2 and TLR9 dependent, and IL-12 production was TLR2 and TLR4 dependent; TLR4 and TLR2 were critical for clearance of vaccine and pathogenic Brucella strains respectively; and TLR2 (p<0.05), TLR4 (p<0.05) and TLR9 (p=0.075) agonists enhanced vaccine strain RB51-mediated protection against respiratory challenge with strain 2308 in the lung.

Role of TLRs in Brucella mediated murine DC activation in vitro and clearance of pulmonary infection in vivo.

A 6-month-old, neutered male, mixed-breed dog was examined for a 2-month persistent fever, nonhealing dermal metacarpal area wound, and leukocytosis (47.0-198.0 × 10(3)/μl). Serum chemistry findings included hypoalbuminemia, hyperglobulinemia, hyperphosphatemia, and hyperphosphatasemia. Complete blood cell count results revealed a moderate microcytic, hypochromic nonregenerative anemia with a profound leukocytosis (198.5 × 10(3)/μl), characterized by neutrophilia with toxicity and hypersegmentation, and significant band cells. Tick-borne disease titers (genera Anaplasma, Ehrlichia, and Borrelia) were negative, as were polymerase chain reaction for other infectious agents (genera Hepatozoon, Mycobacterium, Mycoplasma; and Canine distemper virus). No agents were identified in a deep dermal biopsy (conventional and special histochemical stains) of the chronic draining, metacarpal region lesion. Cytology of the draining tract revealed numerous mixed bacteria and a surprising lack of neutrophils. Chronic occult blood loss with iron deficiency was considered a possible cause of the anemia. Differentials for the leukon were chronic established inflammation (occult infectious agent), chronic neutrophilic leukemia, paraneoplastic leukocytosis (neoplastic source of granulocyte colony-stimulating factor [CSF] or granulocyte-macrophage CSF), and leukocyte adhesion deficiency (LAD). The possibility of a LAD disorder was further investigated because of the noted hypersegmented neutrophils, absence of neutrophils in the cytology sample, the animal's young age, and persistence of clinical and laboratory signs. Flow cytometry of blood neutrophils showed a 60% reduction in surface expression of the β2-integrin (CD18) subunit, whereas neutrophil function tests (oxidative burst and phagocytosis) were normal. Genetic testing revealed a homozygous missense mutation in the β2-integrin subunit gene, previously recognized only in purebred Irish Setters, leading to a diagnosis of LAD type 1 disorder in this mixed-breed dog.

Leukocyte adhesion deficiency type I in a mixed-breed dog.

Endoreduplication, the process of DNA replication in the absence of cell division, is associated with specialized cellular function and increased cell size. Genes controlling endoreduplication in tomato fruit have been shown to affect mature fruit size. An efficient method of estimating endoreduplication is required to study its role in plant organ development. Flow cytometry is often utilized to evaluate endoreduplication, yet some tissues and species, among them the tubers of, remain intractable to routine tissue preparation for flow cytometry. We aimed to develop a method through the use of protoplast extraction preceding flow cytometry, specifically for the assessment of endoreduplication in potato tubers.

Protoplast isolation prior to flow cytometry reveals clear patterns of endoreduplication in potato tubers, related species, and some starchy root crops.

Melissa Makris

Flow Cytometry Laboratory,
Virginia-Maryland College of Veterinary Medicine,
Flow Cytometry Laboratory, Virginia-Maryland College of Veterinary Medicine

Virginia Polytechnic Institute and State University

Fluorescence-activated Cell Sorting for Purification of Plasmacytoid Dendritic Cells from the Mouse Bone Marrow

Measuring Endoreduplication by Flow Cytometry of Isolated Tuber Protoplasts

Melissa Makris

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Flow Cytometry Laboratory,Virginia-Maryland College of Veterinary Medicine,Flow Cytometry Laboratory, Virginia-Maryland College of Veterinary Medicine

Virginia Polytechnic Institute and State University

Fluorescence-activated Cell Sorting for Purification of Plasmacytoid Dendritic Cells from the Mouse Bone Marrow

Measuring Endoreduplication by Flow Cytometry of Isolated Tuber Protoplasts

Flow Cytometry Laboratory,
Virginia-Maryland College of Veterinary Medicine,
Flow Cytometry Laboratory, Virginia-Maryland College of Veterinary Medicine