Kazuki Sato

Marginal zone B cells exacerbate endotoxic shock via interleukin-6 secretion induced by Fcα/μR-coupled TLR4 signalling

Marginal zone (MZ) B cells produce a first wave of antibodies for protection from blood-borne pathogens. However, the role of MZ B cells in inflammatory responses has not been elucidated. Here we show that MZ B cells produce pro-inflammatory cytokines, such as interleukin-6 (IL-6), and exacerbate systemic inflammatory responses to lipopolysaccharide (LPS). After intravenous injection of LPS or E. coli, mice deficient in MZ B cells or IL-6 only in MZ B cells have attenuated systemic inflammatory responses and prolonged survival compared with wild-type mice. LPS directly stimulates MZ B cells via Toll-like receptor 4 (TLR4) and MyD88 pathways for IL-6 production. Furthermore, TLR4 requires physical and functional association with Fcα/μR (CD351) for its oligomer formation, NF-κB signalling and IL-6 production from MZ B cells; this association is responsible for systemic inflammatory responses and endotoxic shock. These results reveal a pro-inflammatory role of MZ B cells in endotoxic shock.

Improved protocol for the isolation of naïve follicular dendritic cells

Follicular dendritic cells (FDCs) in lymphoid organs play an important role in the humoral immune response. However, because the isolation of FDCs is difficult due to their very small population size and fragility under mechanical and chemical stresses, the genetic and biochemical characteristics of FDCs remain unclear. Previously, we identified FDCs as ICAM-1+ cells in the CD45- non-hematopoietic cell fraction from naïve mouse spleen after cell separation by means of digestion with a combination of enzymes. In the present study, using a new combination of enzymes, we found that FDCs are highly enriched in the CD45-ICAM-1+CD21/35+ cell fraction. CD45-ICAM-1+CD21/35+ cells in the mouse spleen retained an antigen administered in vivo for more than 7 days. Moreover, CD45-ICAM-1+CD21/35+ cells isolated from the spleen of mice administered with a cognate antigen enhanced the survival and proliferation of antigen-specific B cells in vitro. Our improved protocol for the isolation of naïve FDCs will be useful for the analysis of FDCs in vitro and in vivo.

Kinematics analysis of manipulation of environment-contacting object with free-joint-structure

In this paper, we show analysis of kinematics of environment-contact task by position-controlled manipulator with free-joint structure at its wrist. Some friction forces at contact points and a force acted by a manipulator cannot be determined. So it is very complex problem to analyze the kinematics of such tasks. Including this uncertainties of acting forces, we have introduced conditions whether the position-controlled manipulator may occur excessive contact force at its contact with environment, whether a desired manipulation can be achieved or not. In 2D manipulation model, we can analyze manipulation possibility for required tasks. In this report, we develop a new method to analyze these conditions with linear programming method. With this method, we can easily judge conditions whether an environment-contact task is able to be achieved or not. We show some examples of analysis of this manipulation possibility.

Cutting Edge: Identification of Marginal Reticular Cells as Phagocytes of Apoptotic B Cells in Germinal Centers

Germinal centers (GCs) in secondary lymphoid organs generate large numbers of apoptotic B cells that must be eliminated by phagocytes to prevent the development of autoimmune diseases. Although tingible body macrophages engulf apoptotic GC B cells, whether stromal cells are also involved in this process is unclear. In this study, we identified marginal reticular cells (MRCs) as novel nonprofessional phagocytes for the clearance of apoptotic GC B cells in the spleen. We used CD19eGFP (CD19creZ/EG) mice, which express enhanced GFP (eGFP) under the control of CD19cre expression, to track B cells in the GCs after immunization with NP-chicken γ globulin plus aluminum salt. We demonstrated that the MRC population, as determined by expression of podoplanin or Rankl, specifically showed an eGFP signal in the cytoplasm after immunization. These results suggest that MRCs contribute to the clearance of apoptotic B cells in GCs.

Identification and isolation of splenic tissue-resident macrophage sub-populations by flow cytometry

Isolation of splenic macrophage subpopulations using an enzyme cocktail

Increased CD11b⁺ Gr-1⁺ cell population in the placenta after infection with Toxoplasma gondii

Toxoplasma gondii is an obligate intracellular protozoan pathogen that can cross the placenta, resulting in congenital toxoplasmosis with severe fetal brain abnormalities. The molecular mechanisms of immune responses against T. gondii infection in the placenta have largely remained unclear. An analytical method for characterizing phenotypes of immune cells in the placenta by flow cytometry was established and it was found that numbers of CD11b+ Gr‐1+ cells in the placenta increased significantly after T. gondii infection. These results suggest that innate immune responses play an important role in immunity against T. gondii infection via the feto‐maternal interface.

Motion estimation for environment-contact task with position controlled manipulator

In this paper, we show analysis of kinematics of environment-contacting task by position-controlled manipulator with free-joint structure at its wrist. Some friction forces at contact points and a force acted by a manipulator cannot be determined. Based on the minimum work principle, we have proposed motion estimation model with linear programming problem. With this motion estimation model, we also develop a method to make a motion plan of the manipulator to generate a desired object motion.