The formation and function of the neutrophil phagosome

Neutrophils are the most abundant circulating leukocyte and are crucial to the initial innate immune response to infection. One of their key pathogen-eliminating mechanisms is phagocytosis, the process of particle engulfment into a vacuole-like structure called the phagosome. The antimicrobial activity of the phagocytic process results from a collaboration of multiple systems and mechanisms within this organelle, where a complex interplay of ion fluxes, pH, reactive oxygen species, and antimicrobial proteins creates a dynamic antimicrobial environment. This complexity, combined with the difficulties of studying neutrophils ex vivo, has led to gaps in our knowledge of how the neutrophil phagosome optimizes pathogen killing. In particular, controversy has arisen regarding the relative contribution and integration of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-derived antimicrobial agents and granule-delivered antimicrobial proteins. Clinical syndromes arising from dysfunction in these systems in humans allow useful insight into these mechanisms, but their redundancy and synergy add to the complexity. In this article, we review the current knowledge regarding the formation and function of the neutrophil phagosome, examine new insights into the phagosomal environment that have been permitted by technological advances in recent years, and discuss aspects of the phagocytic process that are still under debate.     

Effect of hydrocortisone on spontaneous and mitogen-dependent activity of peripheral blood lymphocytes in some vertebrates

The effect of hydrocortisone on functional activity of peripheral blood lymphocytes in different vertebrates during ontogeny was studied by the blast transformation test. Hydrocortisone in a dose of 100 mg/kg inhibited functional activities of T and B lymphocytes in vitro stimulated by mitogens. This inhibitory effect was observed in both young and adult animals. However proliferative activity of concanavalin A-dependent blood T suppressors in rats increased, especially in adult animals (by 3.5 times). Hence, hydrocortisone produced different effects on functional activity of peripheral blood lymphocytes in the studied species, and these effects are dose- and species-dependent.     

Effect of activators on neutrophil mobility

Effect of various activators on chaotic movement of neutrophls on the glass is studied using a Magiscan 2A automatic image analysis system. All tested agents in concentration inducing neutrophil activation suppress their mobility, but no one completely inhibits neutrophil motion. The cells retain the ability to change their shape and partially to move. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 124, No. 10, pp. 409–412, October, 1997     

A comparative study of neutrophil purification and function

Several different methods are currently used by numerous laboratories for the isolation of human neutrophils. These methods include partial purification by dextran sedimentation followed by water lysis, and more complete purification procedures utilizing discontinuous density gradients coupled with dextran sedimentation and in some cases hypotonic lysis. Some investigators refrain from using certain purification schemes because certain steps or reagents used in a particular method might adversely affect the functional parameter of the neutrophil they wish to measure. In spite of these concerns there has been no systematic comparison of the functional status of neutrophils prepared by the various methodologies. In this study we have compared 4 commonly used methods of isolation with neutrophil function. The results of this study indicate that while neutrophil yield and purity were determined by isolation procedure, all cells were equivalent with regard to chemotactic performance, ability to degranulate, and ability to produce superoxide and hypochlorous acid.     

Effect of Pleurotus djamor var. roseus,an edible mushroom on neutrophil functions

Immune stimulation is an effective as well as protective approach against emerging infectious diseases. Mushroom has been valued throughout the world as both food and medicine for thousands of years. The immunomodulatory activities of methanolic extract of Pleurotus djamor var. roseus (MEPDR, 500 mg/kg/body weight for 48 days) were assessed by testing the various neutrophil functions like adherence, phagocytosis (phagocytic index), avidity index and nitroblue tetrazolium reduction in albino rats. Rats were randomly divided into four groups namely, MEPDR treated and corresponding immunised rats were used. Sheep red blood cells (SRBCs) were used for immunisation. The immunised rats were inoculated with SRBCs. The studied neutrophil functions were significantly stimulated in MEPDR-treated groups.     

Early stages in the mechanism of action of glucocorticoids on human platelets. Effect of hydrocortisone on platelet aggregation

Hydrocortisone (1–10 μM) has no effect on spontaneous platelet aggregation and induces a 5–10-sec latency after platelet activation with 1 μM ADP. Hydrocortisone inhibits collagen-induced platelet aggregation; this effect is blocked by excess of progesterone. Hydrocortisone potentiates the effect of adenosine on disaggregation: in the absence of the hormone IC₅₀ for adenosine is 2.5 μM, while in the presence of 3 and 10 μM hydrocortisone it drops to 1.7 and 0.4 μM, respectively. Translated fromByulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 123, No. 1, pp. 54–57, January, 1997     

Regeneration of the rabbit spleen after hydrocortisone injection

The action of hydrocortisone on the rabbit spleen and the regenerative processes arising after cessation of administration of the hormone were studied. During prolonged administration of hydrocortisone the absorptive function of the reticuloendothelial system is depressed and atrophy of the spleen develops, as shown by a reduction in the weight and size of the organ. Most of the splenic follicles are converted into random clusters of lymphocytes. Pyroninophilic cells disappear from the white pulp. After cessation of the action of the hormone the animal's general condition improves, the development of the atrophic changes in the spleen is halted, the splenic follicles are restored, and the number of pyroninophilic cells in them increases. The use of a regeneration stimulator under these conditions accelerates recovery of the body weight of the animal, reversal of the atrophy of the spleen, and restoration of its normal structure.Department of Histology and Pathological Anatomy, Erevan Zooveterinary Institute. (Presented by Academician of the Academy of Medical Sciences of the USSR A. P. Avtsyn.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 84, No. 12, pp. 722–725, December, 1977.     

Endogenous glucocorticoids modulate neutrophil migration and synovial P-selectin but not neutrophil phagocytic or oxidative function in experimental arthritis

Pharmacologic glucocorticoids are powerful inhibitors of the inflammatory response at many levels, including leucocyte trafficking and function. The adhesion molecule P-selectin is a key participant in polymorphonuclear neutrophil (PMN) migration to sites of inflammation. The extent to which endogenous glucocorticoids influence PMN migration and activation is not clear. We used the glucocorticoid receptor antagonist RU486 to examine the effect of endogenous glucocorticoid blockade on PMN migration and function in carrageenan monoarthritis in the rat. Arthritis was induced by intra-articular injection of carrageenan and disease severity measured by PMN count in synovial lavage fluid. Decalcified frozen sections of injected joints were analysed for expression of P-selectin by immunohistochemistry. Adrenal glucocorticoid action was blocked in vivo with RU486 20 mg/kg. PMN phagocytosis and reactive oxygen species synthesis were measured by flow cytometry. Carrageenan injection was associated with severe arthritis (synovial lavage PMN 5.9 ± 0.7 × 10⁶, P < 0.01 versus control) which was dose-dependent. P-selectin was not detected in normal joints but was abundant in joints injected with 500 μg carrageenan. RU486 resulted in exacerbation of carrageenan arthritis (9.7 ± 0.8 × 10⁶, P < 0.05). RU486 also altered the threshold for disease induction, in that most RU486-treated animals were susceptible to arthritis at a dose of carrageenan (2.5 μg) which did not induce arthritis in most control-treated animals (P < 0.05), denoting an altered threshold for arthritis induction. RU486 treatment was associated with increased synovial P-selectin expression. Activation status as measured by PMN phagocytic and oxidative function were not influenced by endogenous glucocorticoid blockade. These findings suggest that endogenous glucocorticoids selectively influence PMN migration to inflamed joints via P-selectin expression, but have no effect on PMN activation status.