Number Of Cytoplasmic Granules Research Articles

DETERMINATION OF CELL TYPE AND HAEMOCYTE MORPHOMETRIC CHARACTERISTICS OF WESTERN AUSTRALIA FRESHWATER CRAYFISH (Cherax cainii) AT DIFFERENT TEMPERATURES IN VITRO

The purpose of this study was to identify and morphologically characterize the hemocyte cell types of freshwater crayfish, Cherax cainii. In addition to morphological observations using a light microscope (LM) and electron transmission microscope (TEM), a flow cytometer (FCM) is also used. Three main types of haemocyte of C. cainii were identified by LM, TEM, and FCM. Determination of haemocyte by LM based on the number, size of cytoplasmic granules and the ratio of N:C. These cells are Hyaline (HC), Small Granule (SGC), and Large Granule (LGC) cells. Three types of haemocyte were also observed by TEM based on cell and nucleus size, granule diameter, number of cytoplasmic granules per cell and N:C. Haemocyte population was successfully detected with FCM based on forward scatter (FSC) signals, versus side scattering signals/side scatter (SSC), with plot data via scatter parameter gating. Three cluster formations were observed, which were temporarily classified as SGC, LGC, and HC regions. Morphometric analysis was performed with TEM on C. cainii haemocyte to measure various cellular features. Some morphological features vary between types of haemocyte and are also affected by temperature. Total hemocyte count (THC) and differential hemocyte count (DHC) are calculated using FCM. THC increases with higher temperatures, from 1,9 x 106 /ml at 20 °C to 4.9 x 106 /ml at 30 °C. The most abundant hemocyte at all temperatures is HC, followed by SGC and LGC.

In vitro exposure of Ulva lactuca Linnaeus (Chlorophyta) to gasoline – Biochemical and morphological alterations

Refined fuels have considerable share of pollution of marine ecosystems. Gasoline is one of the most consumed fuel worldwide, but its effects on marine benthic primary producers are poorly investigated. In this study, Ulva lactuca was chosen as a biological model due to its cosmopolitan nature and tolerance to high levels and wide range of xenobiotics and our goal was to evaluate the effects of gasoline on ultrastructure and metabolism of that seaweed. The experimental design consisted of in vitro exposure of U. lactuca to four concentrations of gasoline (0.001%, 0.01%, 0.1%, and 1.0%, v/v) over 30 min, 1 h, 12 h, and 24 h, followed by cytochemical, SEM, and biochemical analysis. Increase in the number of cytoplasmic granules, loss of cell turgor, cytoplasmic shrinkage, and alterations in the mucilage were some of the ultrastructural alterations observed in thalli exposed to gasoline. Decrease in carotenoid and polyphenol contents, as well as increase of soluble sugars and starch contents were associated with the time of exposure to the xenobiotic. In combination, the results revealed important morphological and biochemical alterations in the phenotype of U. lactuca upon acute exposure to gasoline. This seaweed contain certain metabolites assigned as candidates to biomarkers of the environmental stress investigated and it is thought to be a promise species for usage in coastal ecosystems perturbation monitoring system. In addition, the findings suggest that U. lactuca is able to metabolize gasoline hydrocarbons and use them as energy source, acting as bioremediator of marine waters contaminated by petroleum derivatives.

꼬막 Tegillarca granosa 심신낭복합체의 미세해부학적 특징

ABSTRACT This study was conducted to provide the microanatomical information of the heart-kidney complex of Tegillarca granosa . The heart-kidney complex was located in the pericardial cavity between the dosal visceral mass and posterior adductor muscle. The heart composed of two atrium and one ventricle. The kidney composed of a pair of left and right. The atrium and ventricle of the heart were composed of the epicardium, myocardium and endocardium. The epicardium of simple epithelial layer composed of cuboidal epithelial cells that had a strong basophilic nucleus located in the center. The myocardium composed of muscle fiber bundles. The myocardium in ventricle was denser than in the atrium. The endocardium of simple epithelial layer composed of squamous epithelial cell that had a strong basophilic nucleus was located in the center. The endocardium thickness of the atrium was 6.04 (± 2.26) μm, endocardium thickness of the atrium was 7.36 (± 3.21) μm, and appeared to be thicker in the ventricle. The kidney composed of numerous renal tubules. The renal tubule of simple epithelial layer composed of columnar epithelial cell with nucleus located in the basal zone and a number of cytoplasmic granules. The developed striated border was the inner epidermis.Key words:

Effects of several immunostimulants on phenoloxidase and hemocytes of the crab Charybdis japonica

To investigate the stimulating effects of immunostimulants on the autogenous immunocompetence of crabs and the possible mechanisms involved, the immunostimulating effects of β-1,3-glucan, lipopolysaccharide (LPS), inactivated Vibrio harveyi and Vibrio anguillarum on phenoloxidase (PO) and hemocytes of Charybdis japonica were investigated in this study. It was found that the yields and the enzymatic activities of purified PO in C. japonica increased significantly after the crabs were treated with immunostimulants, while the unit enzymatic activities remained almost the same. After treatment with β-1,3-glucan and LPS, the amount of rough endoplasmic reticulum (RER) and the number of mitochondria in both semigranular cells and granular cells increased greatly, and the number of cytoplasmic granules decreased but with enlarged volume. However, the corresponding characteristics of hyaline cells remained almost the same. On the other hand, the number of granules in semigranular cells decreased greatly, and the number of mitochondria of hyaline cells increased greatly, after treatment with inactivated vibrios. It may be concluded that the effect of polysaccharide immunostimulants on the innate immune system of C. japonica is different from that of inactivated vibrio immunostimulants. The immunity-enhancing mechanism of polysaccharides in crab autogenous immunocompetence is probably accomplished by the increased yields of PO and total PO activities, while that of inactivated vibrios is probably accomplished by the partially increased yields of PO and total PO activities as well as the significantly improved phagocytotic abilities of semigranular cells and hyaline cells.

Non‐specific cellular responses of rainbow trout to Vibrio anguillarum and its extracellular products (ECPs)

We have studied the early inflammatory response induced by Vibrio anguillarum and by its extracellular products (ECPs) in rainbow trout after intraperitoneal injection. The results showed a very similar inflammatory response which included leucopenia, mainly due to lymphopenia, neutrophilia and an increase in the number of circulating monocytes. Melanomacrophages as well as immature leucocytes were frequently observed circulating in the blood of injected rainbow trout. Monocytes often contain phagocytosed bacteria and other, altered cells including erythrocytes and leucocytes. However, neutrophils only occasionally phagocytosed bacteria. Many circulating leucocytes showed important structural alterations. Neutrophils of trout injected with bacteria and ECPs also showed stronger PAS‐staining than those of control trout as well as Döhle bodies and swollen granules. A marked vasodilatation was observed in the kidney and spleen which was coincidental with a mobilization of eosinophilic granular cells and an hypertrophy of sinusoidal endothelial cells showing an increase in the number of cytoplasmic granules. An increase in the number of macrophages and melanomacrophages in the kidney and spleen as well as oedema and leucocyte infiltration in the liver and gills were also noted.

Effect of chronic alcohol feeding on the ultrastructure of rat peripheral blood neutrophils: a morphometric study.

Morphometric methods were used to analyze the ultrastructural characteristics of peripheral blood polymorphonuclear neutrophils (PMN) in 10 rats chronically consuming ethanol and 20 rats fed an isoenergetic standard diet (10 ad libitum and 10 pair fed control rats). Morphometric measurements were made, after a 4-month experimental period, of the following: the profile area of the cell, nucleus and cytoplasm; nucleus to cell profile area; volume density of the nucleus, cytoplasm, mitochondria, Golgi system, endoplasmic reticulum and cytoplasmic granules; number of mitochondria per cell profile; number of cytoplasmic granules per cell profile and per micron2 of cytoplasm, as well as the azurophilic to specific granule ratio and mean diameter of granules. A significant decrease in cell profile area and cytoplasm profile area was shown in ethanol-treated rats. The volume density of mitochondria and endoplasmic reticulum nearly doubled during ethanol abuse. The results also showed that there were highly significant effects of ethanol on the total number of cytoplasmic granules per cell. In addition, changes were observed in mitochondria such as clumping, elongation, swelling and disruption of cristae, as well as changes in the topographic distribution of granules in the cytoplasm such as registration of cytoplasmic areas with numerous granules and areas with a smaller number or without any granules. Some neutrophils of ethanol-treated rats had autophagic vacuoles. The results indicate some ultrastructural abnormalities of PMN in chronic experimental alcoholism that may be related to polymorphonuclear phagocyte dysfunction.

Ultrastructural effects of granulocyte colony stimulating factor (G-CSF) and macrophage colony stimulating factor (M-CSF) on rat neutrophils and monocytes

Human granulocyte colony stimulating factor (G-CSF) and macrophage colony stimulating factor (M-CSF) were administered intravenously to rats, and their effects on neutrophils and monocytes were examined by electron microscopy. G-CSF increased the number of cytoplasmic granules in neutrophils. It also enhanced maturation of the nuclear shape in the neutrophils, while chromatin condensation and peroxidase distribution remained immature. M-CSF induced proliferation of monocytes in peripheral blood and bone marrow, but did not affect morphology or distribution of peroxidase reactivity.

Ultrastructural and ultracytochemical alteration of rat neutrophils induced by G‐CSF

Recombinant human granulocyte colony-stimulating factor (G-CSF) was administered intravenously to rats, and its effects on the neutrophils from bone marrow and peripheral blood were examined by electron microscopy. Immature cells such as the promyelocytes in the bone marrow of the rats 12 hours after G-CSF administration revealed more irregular nuclei than those in untreated rats. Forty-eight hours after G-CSF administration, these changes became more marked. In the peripheral blood, the number of cytoplasmic granules was increased 12 hours after administration of G-CSF. The nuclei of mature neutrophils at 48 hours showed hypersegmentation with slight chromatin aggregation. The peroxidase reaction observed by electron microscopy revealed an increase in the number of positive granules in the immature neutrophils 48 hours after G-CSF administration, and some of the granules tended to be large. Different from untreated granulocytes, a positive peroxidase reaction was observed in the perinuclear space and rough endoplasmic reticulum of mature cells in the peripheral blood 48 hours after G-CSF administration. These granules also tended to be large. The present electron microscopic investigations demonstrated alterations of the neutrophils in G-CSF-administered rats, and these cells retained ultracytochemical evidence of prematurity even at their mature stage.

Enhancing effect of natural killer cell stimulatory factor (NKSF/interleukin‐12) on cell‐mediated cytotoxicity against tumor‐derived and virus‐infected cells

Natural killer cell stimulatory factor (NKSF) or interleukin-12 (IL-12) is a heterodimeric cytokine with pleiomorphic effects on T and NK cells, including induction of lymphokine production, mitogenesis, and enhancement of spontaneous cytotoxic activity. Similarly to IL-2, NKSF/IL-12 enhances NK cell-mediated cytotoxicity within a few hours and independently from induced proliferation. This effect is independent from other induced cytokines, because it is not prevented by antibodies neutralizing interferon (IFN)-alpha, IFN-beta, IFN-gamma, IL-2 or tumor necrosis factor (TNF)-alpha and, unlike the induction of IFN-gamma production by peripheral blood lymphocytes, it does not require HLA class II-positive accessory cells. Enhanced cytotoxicity is accompanied by morphologic changes in NK cells, including a significant increase in the number of cytoplasmic granules. In addition to the previously described ability to enhance the cytotoxic activity of NK cells against tumor-derived target cells, NKSF/IL-12 is also a potent stimulator of cytotoxicity against virus-infected cells, either fibroblasts acutely infected with herpes viruses or T cell lines chronically infected with human immunodeficiency virus-1. NK cell-mediated antibody-dependent cytotoxicity or anti-CD16 antibody-redirected lysis is not significantly enhanced by NKSF/IL-12. However, the ability of resting peripheral blood T cells to mediate anti-CD3 antibody-redirected lysis is enhanced by 18-h incubation with NKSF/IL-12, indicating that this lymphokine can modulate the cytotoxic capability of both NK and T cells.

Cytological responses of the pituitary (rostral pars distalis) and immunoreactive corticotropin-releasing factor (CRF) in the goldfish treated with dopamine antagonists

The in vivo effects of three dopamine (DA) antagonists on the cytology of the rostral pars distalis (RPD) were investigated in young goldfish ( Carassius auratus L.). Pimozide, sulpiride, and domperidone were injected for 5 (low dose, Experiment I) and 7 days (higher dose, Experiment II). Cytological and immunocytochemical techniques using antisera to (1–24) ACTH and (1–39) ACTH, human β-thyrotropin (TSHβ), and synthetic (1–41) CRF were applied to pituitary and brain sections. Cytometrical studies showed that the three drugs induced similar quantitative changes in the cells of the RPD. Prolactin (PRL)-secreting cell hypertrophy was significant in Experiment 11, whereas the nuclear enlargement was significant in both experiments. The numbers of cytoplasmic granules were similar in control and treated goldfish. Thyrotropic (TSH) cells and their nuclei were significantly enlarged in both experiments; their content in immunoreactive TSH was not clearly modified. Corticotropic (ACTH) cells showed significant nuclear and cellular hypertrophy, and labeled granules were often concentrated along the cell membrane. The amount of immunoreactive CRF present in the rostral neurohypophysial ramifications was reduced in the majority of treated fish. Solvent-injected controls showed no significant changes in the RPD. These results suggest that DA inhibits PRL cell activity in goldfish. TSH and ACTH cells appear stimulated by DA-receptor blockers, although differential effects on synthesis and release cannot be evaluated in in vivo experiments. A release of corticotropin-releasing factor may be involved in the ACTH cell stimulation. These data are compared with those obtained in other vertebrates.

Morphometry of feline neutrophil granule genesis.

During neutrophil granule genesis, the formation of primary granules is generally thought to be limited to the promyelocyte stage; whereas synthesis of secondary granules is thought to occur only at the myelocyte stage. This hypothesis was tested morphometrically in feline neutrophils that are known to contain both granule types. Marrow specimens obtained from six cats were stained with peroxidase for identification of neutrophil primary granules and counterstained with periodic acid-thiocarbohydrazide-silver proteinate (PA-TCH-SP) for identification of secondary granules. By regression analysis using arithmetic models, numbers of cytoplasmic granules in 311 cells were correlated with the degree of nuclear chromatin condensation, which was shown to be an adequate parameter for cell maturation. Promyelocytes and myelocytes had similar mean numbers of peroxidase-positive granules per unit area. A significant increase (p less than or equal to 0.0001) in the numbers of peroxidase-positive granules was noted between the metamyelocyte and the mature neutrophil stage, despite the lack of peroxidase activity in endoplasmic reticulum and Golgi lamellae. By contrast, a significant increase of peroxidase-negative granules between the metamyelocyte and the mature neutrophil stage was not clearly established with these methods. The increase in peroxidase-positive granules may indicate continued production of peroxidase-containing granules and/or redistribution of peroxidase among lysosomal organelles in late feline neutrophils.

Hamartoma of the parotid gland: A case report with immunohistochemical and electron microscopic study

A case of a solid parotid tumour in a 16-year-old boy is presented. Histologically, the tumour demonstrated some peculiar findings. An acinar pattern was predominant although every component seen in the normal salivary gland was present, namely, serous and mucous gland acini, ducts, myoepithelial cells, adipose and lymphoid tissue. Large eosinophilic granules were abundant in the large acinar cell cytoplasm. Immunohistochemically, the tumour demonstrated the proteins which are present in the normal parotid gland, for example, amylase, lactoferrin and lysozyme. Electron microscopic features were quite similar to those of normal parotid tissue except for accumulation of a large number of cytoplasmic granules in the acinar cells. There has been no previous report of a tumour with the same features as seen in this case. Our pathological diagnosis is hamartoma, although the possibility of hyperplasia or neoplasia can not be excluded.

Structural studies of the adrenal zona glomerulosa and renal juxtaglomerular apparatus in pregnant sheep.

The ultrastructural changes in the adrenal zona glomerulosa and renal juxtaglomerular apparatus have been examined during normal pregnancy in sheep. As pregnancy progressed, increasing numbers of cells in the adrenal zona glomerulosa displayed mitochondria with straight tubular "rod-like" structures replacing their normal lamelliform cristae; groups of cells showing these mitochondrial changes were predominantly located in the middle and superficial regions of the zona glomerulosa, but at all stages remained interspersed with cells with apparently normal mitochondria. In the same animals, the renal juxtaglomerular index was raised, reflecting an increase in renin storage, and juxtaglomerular myoepithelioid cells showed increased numbers of cytoplasmic granules, but no apparent increase in granular endoplasmic reticulum and Golgi profiles; there were no distinguishing morphological changes in juxtaglomerular peripolar cells. These findings provide morphologic evidence of stimulation of the adrenal zona glomerulosa in association with increased juxtaglomerular renin storage during pregnancy. The mitochondrial changes observed in an increasing proportion of cells in the zona glomerulosa closely resemble those seen in sodium-depleted animals, and may reflect the altered steroidogenic capacity of the adrenal gland in pregnant sheep. The finding of groups of cells displaying altered mitochondria lying next to cells with normal mitochondria suggests the presence of cells with different sensitivities to stimuli for aldosterone production or may indicate the presence of different cell types in the zona glomerulosa responding to different stimuli.

The Mechanisms which Produce Vacuolated and Degranulated Eosinophils

Summary. As blood eosinophils in patients with an eosinophilia may contain refractile‘vacuoles’(vacuolated eosinophils), and some cells contain only a few granules (degranulated eosinophils) which show ultrastructural changes, experiments were done to see whether similar morphological alterations could be induced in blood eosinophils from normal people. Overnight culture of normal eosinophils with serum treated with cobra venom factor induced refractile‘vacuoles’and ultrastructural changes in granule matrix material. On the other hand, concanavalin A, 10 μ/ml for 2 h, led to the formation of larger perinuclear vacuoles containing granule contents, and ultrastructural changes were more marked in granule crystalloid material. Cytochalasin B inhibited these effects of concanavalin A. Neither of these stimuli caused a marked reduction in the number of cytoplasmic granules, but lysolecithin and insoluble (but not soluble) immune complexes produced large endocytic vacuoles into which partially solubilized and whole eosinophil granules were discharged.These results suggest that eosinophil granules can be affected in two distinct ways. In one, the granule matrix is altered leading to the light microscopy appearances of small refractile ‘vacuoles’. In the second, the crystalloid material is dispersed into the matrix. These apparently distinct steps precede the release of the granule contents into large cytoplasmic spaces or to the outside of the cell. Also, as patients' eosinophils may show one or both of these alterations it is suggested that they are distinct events. As concanavalin A induced solubilization of granules did not result in release to the outside, it is also proposed that an additional stimulus may be required to produce exocytosis of eosinophil granule contents. Further studies may show how these processes are linked, and their relative importance in eosinophil effector functions.

Monoamine-storing cells in the media of the thoracic aorta of Gallus domesticus.

Light, fluorescence and electron microscope studies of chicken and chick embryo aorta reveal the occurrence of cell masses without the characteristics of smooth muscle cells situated within the media, in the transitional region between the aortic arch and the descending thoracic aorta. The cell masses consist of two cell types: one type (G cells) contains large numbers of cytoplasmic granules (900–2200 A in diameter); the other cell type consists of Schwann cell-axon complexes. G cells are innervated by monoaminergic nerve fibres considered to be efferent ones. Some G cells are in contact with endothelial cells or medial smooth muscle cells. G cells appear in the aortic wall at 9 days in ovo; they do not regress in old chickens.

STUDIES ON DROSOPHILA EMBRYONIC CELLS IN VITRO I. CHARACTERISTICS OF CELL TYPES IN CULTURE.

Embryonic cells from Drosophila melanogaster were cultured in medium K-17 supplemented with 0.1 mg/ml of fetuin and 15% fetal bovine serum, and the behavior of embryonic cells, the characteristics of some cell types and the maintenance of the phenotypic properties of the cells were examined. Embryos at the stage with a saclike midgut (12 hr eggs) were found to be the best materials for cultivation. Muscle cells, epithelial cells, fibroblastic cells and small cells were observed as distinct migrating cell types. Muscle cells pulsated synchrónously when two or more cells made contact with each other and this pulsation continued for more than six weeks under the culture conditions employed. Epithelial cells matured with increase in size and in the number of cytoplasmic granules. Fibroblastic cells had conspicuous motile activity. Small cells were peculiar for their size of about 3 μm diameter and formed groups of about forty to fifty cells. Their characteristic shape and size suggested that they were imaginal disc cells. Cellular spheres, which consisted of epithelial cells and fibroblastic cells, and nerve fibers of nerve cells were also observed. Some mitotic figures, suggesting the occurrence of cell division, were observed in cultures of epithelial cells.

Cytoplasmic granularity of the renal medullary interstitial cells in experimental hypertension.

Abstract The renal medullary (papillae and medullae) interstitial cells have prominent features suggesting an actively secretory cell. These include the presence of numerous mitochondria, prominent Golgi bodies, smooth-surfaced endoplasmic reticula, and osmiophilic granules which are stained for neutral lipids with oil Red-O. The interstitial cells were studied as a possible production site for the antihypertensive factor-a neutral lipid. Experimental hypertension was induced in Sprague-Dawley rats by administration of excessive sodium chloride or by injections of DOCA or with a combination of both agents. The same agents were administered to separate groups of animals with and without unilateral nephrectomy. The granularity within 100 interstitial cells was evaluated quantitatively in 0.5 μ sections stained with methylene blue and azure II. Granules within interstitial cells were also counted in electron micrographs of 50 cells chosen at random. Hypertension developed in a significant number of animals after administration of DOCA and also after administration of saline with DOCA, in both uninephrectomized and non-nephrectomized animals. Animals were more susceptible to experimental hypertension following unilateral nephrectomy. Ultrastructural studies of the renal medullary interstitial cell in control animals revealed a relatively constant number of cytoplasmic granules (8.8 ± 1.2). In animals undergoing unilateral nephrectomy and given NaCl with DOCA, the osmiophilic granularity was significantly increased (p

A Study on the Relationship between Blood Pressure and Chromaffine Cells of the Adrenal Medulla after X-ray Irradiation

The present studies were undertaken to investigate the relationship between blood pressure and adrenal medullary cells (norepinephrinecontaining cells) in adult male rats after whole body X-ray irradiation (700 R.). 1. Both systolic and diastolic values of blood pressure elevated at 3, 24 and 48 hours after irradiation, but systolic pressure became lower than the normal level at 0.5 and 72 hours (p<0.01). 2. Pulse rate decreased at 3, 72 and 120 hours after irradiation (p<0.01). Although pulse rate showed tendency to decrease in 24 and 48 hours, it was not statistically significant. 3. Increase in number of norepinephrine-containing cells with marked accumulation of cytoplasmic granules was seen at 3, 12, 24 and 48 hours after irradiation (p<0.01). On the other hand, decrease in number of cytoplasmic granules associated with marked degeneration was observed at 72 and 120 hours. 4. These results indicated the positive correlation between blood pressure and morphological changes of norepinephrine-containing cells.

Production of renin by human juxtaglomercular cells in vitro.

New organ culture methods permit growth of human renal cortical cells fulfilling all known criteria of juxtaglomerular cells. Two types of granules were observed with the electron microscope. These granules showed an increase in size and number during the growth of these cultures. Their presence in cells was demonstrated by Bowie's, basic fuchsin-crystal violet, and fluorochrome staining methods. Puromycin or actinomycin D caused a reduction in the number of cytoplasmic granules, while 1% oxygen in the gas phase of the culture caused an increase. Specific reaction of these granules with rabbit antihuman renin antibody was demonstrated. Other cellular structures did not react with this antibody. Similar granules were observed in the media of hyperplastic, interlobular arterioles but not in normal arterioles or arterioles of other vascular beds. Bundles of myofilaments could be observed between the cytoplasmic granules in cultured cells. Bioassays of renin activity of the supernatant culture medium showed that it contained renin if granulated cells were present in the culture. All juxtaglomerular cells in culture produced granules, but only those cells which grew from kidneys with pathological changes released renin, suggesting that the stimulus for renin release existed in the intact kidney. This stimulus for renin release seemed to be rapidly lost during culture growth.

DEGRANULATION OF POLYMORPHONUCLEAR LEUCOCYTES FOLLOWING PHAGOCYTOSIS OF MICROORGANISMS

A marked reduction in numbers of cytoplasmic granules in rabbit and human polymorphonuclear leucocytes takes place following ingestion of various microorganisms or of a yeast cell wall preparation. The degranulation occurs within 30 minutes of phagocytosis, and is directly related to the quantity of material engulfed. White cells completely degranulated following phagocytosis of large numbers of microorganisms remain viable for at least 1 hour. The granules of polymorphonuclear leucocytes contain the antimicrobial agent, phagocytin, and various digestive enzymes. These substances thus are released into the cytoplasm or into vacuoles following ingestion of foreign material. The granule system and granule lysis mechanism may well play a central role in the primary function of these specialized cells; namely, that of destroying invading microorganisms.