Chapter 9: Microspheres and Phagocytosis
Zoltán A. Tökés in Micro spheres: Medical and Biological Applications, 2017
This chapter reviews the phagocytic process and discusses the advantages, applications, and limitations of the utilization of microspheres in the study of phagocytosis. The most active mononuclear phagocytes are the promocytes in the bone marrow which enter the blood as monocytes. Light and transmission electron microscopy, utilization of large microspheres, and treatment of fixed phagocyte cells with xylene, chloroform, or dioxane to dissolve extracellular polystyrene particles are among the techniques that have been utilized for this purpose. The phagocytic process can be divided into three general phases: the attachment of foreign particles to the surface of the phagocytic cell, the ingestion of such particles by the phagocytes, and the digestion of the ingested material within the cell. One of the major energetic factors to consider about phagocytosis with respect to small particles is their translational kinetic energy. Electronic analysis and recording of measurements may be performed with or without cell sorting.
Basic Knowledge of Host Defenses Against Infection
M. T. Labro in Host Defense and Infection, 2022
Multicellular organisms find themselves surrounded by single-cell microbes, only some of which are pathogenic. Phylogenic evolution has selected several features that protect the host from aggressive intruders. Human beings and mammals, at the top of the phylogenetic tree, possess these three levels of defense, and they are potent enough to protect them from most pathogens. “Innate immunity” refers to natural resistance to infection regardless of the pathogen and is immediately triggered when the protective barriers are breached. In the late 19th century, Metchnikoff recognized phagocytosis as a crucial mechanism in antibacterial defense. The term “professional phagocytes” covers cells whose main functions are engulfing and destroying foreign materials. Mast cells derived from multipotent stem cells play an important role in the inflammatory reaction by secreting a variety of mediators.
Functional and Chronobiological Variations of Immune Defense
M. T. Labro in Host Defense and Infection, 2022
Interindividual variability of phagocyte number, functions and sensitivity to drugs has been evidenced in many studies. Similarly, the broad range of immunoglobulin and complement levels, the percentage and functional activity of T cell subsets also suggests variation at the specific immune response level. The intraindividual variability of host defenses is also widely recognized. For instance, PMNs are often studied as a single-cell population but not only can their functions differ according to the cell pool analyzed but functional differences are found between the various subsets, of the same pool, although this has not been as well analyzed as T cells. Environmental factors such as physical and psychological stress, seasonal influences and circadian rhythms may modify their tissue distribution and functional activity.
The effect of healthy pregnant plasma and preeclamptic plasma on the phagocytosis index of neutrophil granulocytes and monocytes of nonpregnant women
Published in Hypertension in Pregnancy, 2017
Rudolf Lampé, Ágnes Kövér, Sándor Szűcs, László Pál, Ervin Árnyas, Robert Póka
ABSTRACT Objective: Phagocyte function of neutrophil granulocytes and monocytes is decreased in healthy pregnancy and further decreased in preeclampsia. The cause of the declined function is unknown. Decreased phagocyte function can lead to the higher infection rate in healthy pregnancy and may also be responsible for the increased susceptibility to infections and high trophoblast concentration in preeclampsia. The aim of this study is to examine the phagocyte function of neutrophil granulocytes and monocytes. Methods: Monocytes and neutrophil granulocytes were separated from the peripheral circulation of six nonpregnant patients and incubated in plasma samples from six healthy pregnant, six preeclamptic pregnant, and six nonpregnant patients. The cells were marked and evaluated for the phagocytosis index with immunofluorescent microscope after phagocyting the zymosan molecules. Results: Phagocyte function of neutrophils as well as monocytes from nonpregnant patients were decreased significantly when the cells were incubated in plasma samples from healthy pregnant patients, and further decreased when incubated in plasma samples from preeclamptic pregnant women. Conclusion: The decreased phagocyte function of neutrophil granulocytes and that of monocytes in healthy pregnancy and the further decreased phagocyte function in preeclampsia is caused by factor(s) in the maternal circulation.
Mechanisms and Consequences of Phagocyte Adhesion to Endothelium
Published in Annals of Medicine, 1999
Leukocyte adhesion to endothelium is essential for the development of an appropriate immune-inflammatory response. The vital importance of leukocyte-endothelial adhesive interactions in host defense and homeostasis is illustrated by the clinical manifestations of patients with congenital defects of leukocyte adhesion functions. However, under some circumstances leukocyte adhesion to endothelium may instead lead to vascular and tissue damage. In recent years, there has been remarkable progress in the understanding of the molecular basis of leukocyte adhesion to endothelium, and this knowledge has led to a new approach to immunomodulation in human disease, ie ‘antiadhesion’ therapy. This review focuses on cell adhesion molecules mediating adhesion of circulating phagocytes to vascular endothelium, on congenital defects of phagocyte adhesion in man, and on the current status of antiadhesion therapy directed towards phagocyte and endothelial adhesion molecules. We will also consider markers of phagocyte activation, which may provide a means to identify those patients who would benefit most from antiadhesion therapy.
Every day I'm rufflin': Calcium sensing and actin dynamics in the growth factor-independent membrane ruffling of professional phagocytes
Published in Small GTPases, 2017
Daniel Schlam, Johnathan Canton
ABSTRACT Professional phagocytes continuously extend dynamic, actin-driven membrane protrusions. These protrusions, often referred to as membrane ruffles, serve a critical role in the essential phagocyte processes of macropinocytosis and phagocytosis. Small GTPases, such as RAC1/2, spatially and temporally regulate membrane ruffle formation. We have recently shown that extracellular calcium regulates the elaboration of membrane ruffles primarily through the synthesis of phosphatidic acid (PtdOH) at the plasma membrane. RAC1/2 guanine nucleotide exchange factors harbouring polybasic stretches are recruited by PtdOH to sites of ruffle formation. Here we discuss our findings and offer perspectives on how the regulation of dynamic actin structures at the plasma membrane by small GTPases is a critical component of phagocyte function.