Phagocytic Engulfment Research Articles

Antineutrophil Cytoplasmic Antibodies Induce Reactive Oxygen-Dependent Dysregulation of Primed Neutrophil Apoptosis and Clearance by Macrophages

This study assessed whether anti-neutrophil cytoplasmic antibodies (ANCAs) interfere with the safe deletion of neutrophils by apoptosis and phagocytic clearance. Tumor necrosis factor (TNF)-primed neutrophils were incubated with normal IgG (N IgG) or ANCA IgG for up to 36 hours. Compared with N IgG, ANCAs accelerated constitutive apoptosis of TNF-alpha primed neutrophils, as assessed by morphology and confirmed by DNA laddering pattern on gel electrophoresis, and accelerated progression to secondary necrosis. The accelerated apoptosis induced by ANCA was dependent on reactive oxygen species generation, as primed neutrophils from patients with chronic granulomatous disease failed to show an effect of ANCAs on apoptosis. However, there was no change in the rate at which neutrophils exhibited annexin V binding, indicating that externalization of phosphatidylserine was not accelerated by ANCAs. Furthermore, when ANCA-treated primed neutrophils were interacted with human or murine peritoneal macrophages after 12 hours there was significantly less phagocytosis by human macrophages and no difference in phagocytosis by murine peritoneal-derived macrophages when compared with N IgG-treated controls. In conclusion, ANCAs accelerate apoptosis and secondary necrosis in TNF-primed neutrophils by a mechanism dependent on the generation of reactive oxygen species, with uncoupling of nuclear and surface membrane changes, resulting in a "reduced window of opportunity" for phagocytic recognition and engulfment before disintegration.

Vitamin C deficiency in the catfishClarias gariepinus

Regardless of the absence of spinal deformities, vitamin C deprivation in adult-sized Clarias gariepinus challenged the physical integrity and survival of fish, inducing changes that greatly resembled those of fingerlings of other species. Vitamin C was presumed to be a dietary facilitator, which when deprived in the diet of C. gariepinus, would obstruct intestinal absorption of iron and/or impair its release from the reticulo-endothelial stores. This impaired erythrocyte synthesis led into anaemia (as indicated by lowered levels of red blood cells, haemoglobin and haematocrit). Leukopenia noted in fish on a scorbutic (lacking vitamin C) diet suggested functional depression of phagocytic engulfment with increased susceptibility to the deteriorating action of pathogenic agents. Changes in histology included hypertrophy, oedematous separation and telangiectasia of gill lamellae. Shrunken glomeruli, sloughed Bowman’s capsules and tubular dilation and distortion were also shown. Shrunken hepatocytes and the occurrence of yellowish ceroid pigments were the concrete histopathological signs in liver. Vitamin C is thus suggested as a potent antioxidant that offers protection against oxidative damage to various fish tissues.

Free radical mediated sperm-load management in the vagina of rats.

The postcoitus phagocytic engulfment of spermatozoa following disintegration of a sperm cell has not been well understood until now. By monitoring the free radical status of the vagina in accordance with the various stages of the estrous cycle and the sperm-cutting power of vaginal flushing, a positive correlation has been detected that favors the superoxide theory of the sperm-cutting technique in vivo. This finding is also consistent with the previous experience of free radical bombing of spermatozoa in spermatic granuloma.

Identification of factors affecting technetium 99m leucocyte labelling by phagocytic engulfment and development of an optimal technique.

Human autologous leucocytes can be simply and reproducibly labelled by phagocytic engulfment of technetium 99m stannous colloid with high leucocyte-labelling efficiency (LLE), similar human biodistribution to indium-111-oxine labelled leucocytes and good cell viability. A mean particle size of 2.1 microns is optimal for phagocytosis and the most important parameter in maintaining reproducibly high neutrophil uptake. It is more critical than hitherto appreciated. When such variables as type of colloid, purity of starting materials, speed of mixer rotation when preparing colloid and labelling leucocytes, heparin concentration, freshness of colloid preparation, type of sterilising membrane filter used and incubation time of cells with colloid are rigidly controlled, consistent labelling efficiencies in excess of 90% can be obtained with neutrophil predominance. The lyophilised kit tested produced suboptimal results.

Elevated Levels of Dietary Ascorbic Acid Increase Immune Responses in Channel Catfish

Channel catfish fingerlings were fed purified diets containing 0 to 3000 mg/kg of ascorbic acid until external signs of scurvy were seen in the fish fed the ascorbic acid-deficient diet. At this time, resistance to bacterial infection, antibody production, complement activity and phagocytic activity were assessed for fish from the various dietary treatments. Mortality rates of fish experimentally infected with Edwardsiella ictaluri, the bacterium causing enteric septicemia in channel catfish, decreased with increases in dietary ascorbic acid doses, ranging from 100% for fish fed the ascorbic acid-deficient diet to 15% for fish fed 300 mg ascorbic acid per kilogram diet and 0 for fish fed 3000 mg ascorbic acid per kilogram diet. Antibody response to E. ictaluri antigen, hemolysis of sensitized sheep erythrocytes by complement activity and phagocytic engulfment of E. ictaluri by peripheral phagocytes were each impaired in fish fed the diet without supplemental ascorbic acid; intracellular bactericidal activity of the phagocytes was not affected by ascorbic acid deficiency. There were no differences in antibody production, complement activity, or phagocytic activities among fish fed diets containing 30–300 mg ascorbic acid/kg of diet. However, the dose level of 3000 mg ascorbic acid/kg significantly enhanced antibody production and complement activity.

Phagocytic Engulfment and Cell Adhesiveness as Cellular Surface Phenomena

Phagocytic Engulfment and Cell Adhesiveness as Cellular Surface Phenomena

In-vivo and in-vitro studies of the effect of specific antitoxin on the phagocytosis of cells of Clostridium botulinum type A.

SUMMARY The conversion of heat-resistant spores of Clostridium botulinum type A into germinated heat-sensitive cells in the peritoneal cavity of mice has been observed. This in-vivo germination of spores was depressed in mice passively immunised with type-A botulinal antitoxin. Studies, in which the release of free 45Ca in the urine of mice challenged with labelled Cl. botulinum spores provided an indicator of spore germination, showed that spore germination occurred normally at 8 hr in vivo. However, the rate of germination as determined from 45Ca excretion was substantially inhibited when antibody-treated spores were used as the challenge. In in-vitro studies with guinea-pig leucocytes, spore germination was similarly assayed by monitoring the release of 45Ca from labelled spores. Spore germination in these leucocyte systems was also suppressed when the spores were first treated with Cl. botulinum type-A antitoxic serum, although phagocytic indices for antibody-treated spores and vegetative cells were increased. Release of type-A botulinal toxin was either completely prevented or substantially suppressed when Cl. botulinum spores and vegetative cells were treated with specific botulinal antibody and incubated with leucocytes. These results demonstrate that combination of spores with type-specific antibody prompted phagocytic engulfment of antibody-coated spores, but strongly inhibited subsequent phagocytic digestion of engulfed spores.

Evaluation of phagocytic activity by ingestion of labeled bacteria.

Immunologists have used the phagocytic index to evaluate the efficiency of the phagocytic engulfment of foreign particles. Traditionally, stained exudates on slides from in-vitro or in-vivo suspensions of leukocytes and bacteria were analyzed for either the average number of bacteria engulfed per leukocyte in 50-100 phagocytes, or the percentage of leukocytes that have engulfed particles in a given period of time. Due to lack of better methods, several errors inherent in this technique have been tolerated in the past. Thus, some phagocytes engulf many bacteria; i.e., some macrophages may engulf 20-30 cells. This results in an analysis based not on percentage of bacteria engulfed, but rather on the number of phagocytic cells capable of engulfing cells [1, 2]. Evenness of the stain and selection of the counting area on stained slides are other sources of error.

A new method for assessing particle ingestion by phagocytic cells

An isotopic method has been used to assess the in vitro ingestion of bacteria by polymorphonuclear leukocytes. Phagocytic engulfment of bacteria labeled with 14C-alanine or 14C-2-thymidine was measured by counting the radioactivity they contained after a prescribed period of incubation. The method offers improved accuracy and greatly increases the number of experiments which can be performed by eliminating the need for a microscopic count.

Leucocytic response to spermatozoa in ligated segments of the rabbit vagina, uterus and oviduct.

The fate of spermatozoa not participating in fertilization has been held to be enzymatic dissolution and phagocytic engulfment (Austin, 1957). Various investigators have observed sperm cells undergoing phagocytosis by polymorphonuclear leucocytes in the vagina and uterus (Yochem, 1929; Pitkjanen, 1960; Howe & Black, 1963). There is some evidence which indicates that ovarian hormones influence the phagocytic removal of spermatozoa from the female genital tract (Bedford, 1965; Marcus, 1966). It was the purpose of this investigation to compare the leucocytic response of the rabbit vagina, uterus and oviduct to spermatozoa under different hormonal conditions. In the present study, rabbit semen, collected by artificial vagina techniques, was diluted in a Krebs-Henseleit-Ringer (KHR) solution to a concentration of 300 million spermatozoa/ml. The diluted semen (0·1 ml) was injected into ligated segments of the vagina