Reassessment of two Boyden chamber methods for measuring canine neutrophil migration: the leading front and the lower surface count assays

Chemotaxis Assay for Marsupenaeus japonicas Hemocytes and Application for the Development of an Oral Immunostimulant Against White Spot Syndrome Virus

The chemotactic activity of vertebrate leukocytes is an important host-defense mechanism. However, chemotaxis of invertebrate immune cells, particularly those of shrimp species, is incompletely understood and critically understudied. In this study, we aimed to optimize the conditions for a Boyden chamber chemotaxis assay using hemocytes (granulocytes) from cultured kuruma shrimp, Marsupenaeus japonicas (Mj) and the optimal conditions were: 5 μm-pore-size Polyvinylpyrrolidone membrane; culture buffer at pH 7.0; and chemotactic factor N-formyl-methionyl-leucyl-phenylalanine (fMLP) 10^-8 mol/L; 4 h incubation time. We then applied the chemotaxis assay to develop an oral immunostimulant against white spot syndrome virus (WSSV), which results in high mortality rates in several shrimp species worldwide. We focused on the kelp Laminaria japonica, as this species contains immunostimulative molecules such as β-glucan. We prepared Heat Extracts (HE) and Crude Laminarans (CL) from kelp using hot water and hydrochloric acid extraction methods, respectively. HE and CL ware mixed with normal shrimp feed. Kelp extracts were orally administered for 7 days, and hematocyte chemotaxis toward fMLP was compared. No difference was detected between control and kelp extracts on day 3, but HE stimulated chemotaxis 2-fold and CL stimulated chemotaxis 3-fold relative to control on day 7 after initiating administration. Kelp extract administration protected against WSSV exposure. Finally, we identified that Kelp extracts stimulated hematocyte superoxide production on days 3 and 7, and increased hematocyte phagocytosis and phenol oxidase activity on day 7 after administration. We concluded that the chemotaxis assay is informative in assessment of shrimp hemocyte immunological activity, and is applicable to the development of immunostimulants against shrimp infectious diseases.

Evaluation in vitro of canine neutrophil function

Polymorphonuclear granulocyte (PMN) phagocytosis may be affected by many pathological changes. A panel of tests requiring relatively small volumes of blood was applied to 16 healthy dogs in order to obtain normal values and to standardize techniques. PMNs were isolated by discontinuous Percoll gradients; chemotaxis was tested in a modified Boyden chamber using the leading front method; fluorescinated yeast uptake was evaluated on a slide and superoxide (SO) production and adherence was carried out on a microtitre plate. The different aspects of phagocytosis showed no correlation with one another. Better results were obtained using a 60 min incubation period using interleukin-8 (25 ng/mL) as an activator for chemotaxis, and incubating plates for 30 min with phorbol myristate acetate (10(-6)mol/L) to assess SO production.

Characteristics of the response of ovine granulocytes (PMNs) to zymosan-activated serum (ZAS) and to recombinant human interleukin-8 (IL-8)

The chemotactic activity of zymosan-activated serum (ZAS) and of two concentrations of recombinant human IL-8 (IL-8(25), 25 ng/ml; IL-8(50), 50 ng/ml) for ovine polymorphonuclear granulocytes (PMNs) was tested in a modified Boyden chamber. Thick cellulose acetate filters and the leading front method were used to quantify the movements of the cells. Both ZAS and IL-8(25) exerted a chemotactic effect on ovine PMNs (P < 0.01): IL-8(50) induced a more homogeneous response (P < 0.001). To verify the characteristics of the responsiveness to the chemokines after short-term (st) or long-term (lt) repeated samplings, chemotaxis was investigated 1 (T1st), 2 (T2st), 24 (T3st) and 48 h (T4st) after the basal sampling (T0st) and 15 days (T1lt) after the basal sampling (T0lt). No differences in chemotaxis were found in long-term repeated samplings. In contrast an increase in the responsiveness to IL-8(25) and to IL-8(50) (P < 0.05) was detected at T2st in comparison with T0st. Furthermore, the significance of the distance run by activated PMNs compared with the controls, increased from T0st to T2st, as a sign of a more homogeneous response to the chemokines. In the absence of evident changes in circulating leucocyte numbers and in serum cortisol concentrations, these findings could be interpreted as a consequence of a different expression of chemoattractant receptors on the membrane of PMNs collected at different times.

Characterization of the priming effect by pituitary canine growth hormone on canine polymorphonuclear neutrophil granulocyte function

In this report, we demonstrate that canine growth hormone (cGH) is capable of priming canine polymorphonuclear neutrophil granulocytes (PMN) in a manner resembling that of human PMN. The cGH influences important functions that are involved in the process of recruitment of PMN, i.e., shape change, chemotaxis, CD11b/CD18 expression, adhesion, and subsequent transendothelial migration. Also, intracellular O(2)(-) production was evaluated. We investigated the priming effect by incubating PMN with purified pituitary cGH at various concentrations (10 to 800 microg/liter). The capacity for shape change was significantly (P < 0.05) enhanced, whereas the chemotactic response under agarose was significantly (P < 0.05) reduced. The chemotactic migration in Boyden chambers (10-microm-thick polycarbonate filter; lower surface count technique) was significantly (P < 0.05) enhanced, presumably due to cGH-induced hyperadhesiveness to the lower surface of the filters. The adhesion in albumin-coated microtiter plates and adherence to canine pulmonary fibroblasts were significantly (P < 0.05) increased, and the increased adhesion resulted in a significant (P < 0.01) increase in transendothelial migration using canine jugular vein endothelial cells. The increase in adhesion was associated with a significant increase in CD11b/CD18 expression. Furthermore, intracellular O(2)(-) production was significantly enhanced in response to both phorbol myristate acetate (P < 0.01) and opsonized zymosan (P < 0.05). In the absence of a PMN-stimulating agent, cGH did not influence the effector functions investigated except for an increased expression of CD11b/CD18.

Determination of the adhesive capability of canine polymorphonuclear neutrophil granulocytes using a fluorometric microtiter plate cellular adhesion assay

A rapid fluorometric cellular adhesion assay in microtiter plates was evaluated for canine polymorphonuclear neutrophil granulocytes (PMN) using the fluorescent indicator calcein acetoxymethyl ester (Calcein AM). Optimum adhesive responsiveness occurred in bovine serum albumin (BSA)-coated plates after 30 min incubation at 37 degrees C with 5 x 10(5) PMN in 100 microl per well using phorbol myristate acetate (PMA, 100 ng/ml) as stimulant. The adhesive responsiveness for 15 laboratory beagle dogs was determined and the mean percentage of adherence for unstimulated (2.9%) and stimulated (74.3%) PMN and corresponding 95% confidence intervals was determined. The mean intra-assay coefficient of variation (CVintra) for unstimulated and stimulated adhesion in the assay was: CVintra = 12.9% and CVintra = 4.1%, respectively. The mean inter-assay coefficient of variation (CVinter) for unstimulated and stimulated adhesion, respectively, in the assay was: CVinter = 22.9% and CVinter = 5.6%. The assay was highly reproducible and labelling with Calcein AM neither reduced PMN viability nor activated the PMN.

Evaluation of neutrophilic function (chemotaxis, phagocytosis and microbicidal activity) in healthy dogs and in dogs suffering from recurrent deep pyoderma

The modified Boyden's technique of chemotaxis ('leading front' method) and the bacterial killing test with Staphylococcus sp. stained with acridine orange were performed with suspensions of granulocytes from 50 healthy dogs. Lipopolisacharide of Escherichia coli, in normal dog serum was used as the chemotactic factor. The mean value for the chemotactic differential found was 30.41 +/- 12.14 mu. The optimal concentration of bacteria and opsonins (normal dog serum) was 4 and 15%, respectively, and the ideal incubation period was 30 min. The mean values obtained for phagocytosis percentage, number of bacteria per PMN, phagocytosis index and percentage of dead bacteria, were 97.01 +/- 3.22%, 22.20 +/- 4.6, 21.53 +/- 4.50 and 45.30 +/- 9.18%, respectively. Granulocyte functions in 18 dogs with recurrent, chronic, deep pyoderma were assessed by the same methods. No significant difference between the two groups, for any of the evaluated parameters, was found. For elucidation of the pathogenesis of recurrent pyoderma, further studies involving humoral and cellular immunity and the complement system are required.

An investigation of phagocytosis and intracellular killing of Staphylococcus intermedius by canine neutrophils in vitro

Bacterial infection (pyoderma) of the canine skin is largely caused by Staphylococcus intermedius and may be a primary, idiopathic disease or secondary to a range of other dermatological disorders. The immune response to this organism involves phagocytosis and killing by neutrophils. In this study, the effect of opsonisation of S. intermedius by clinical sera (n = 60) and sera from normal dogs (n = 20) was investigated by in vitro phagocytosis and killing assays. All sera from dogs with pyoderma were significantly more efficient at opsonisation for phagocytosis than normal dog sera (p < 0.001). Further, fresh serum was more effective at opsonisation of S. intermedius than heat-inactivated serum in this assay (p < 0.001). The results indicate that opsonisation is enhanced by serum from dogs with pyoderma; therefore the humoral response in clinical cases of canine pyoderma is, in terms of phagocytosis, protective. The small but significant reduction in phagocytosis of S. intermedius opsonised by heat-inactivated serum compared to fresh frozen serum suggests that complement plays a role, although minor, in opsonisation. An in vitro killing assay showed that normal canine neutrophils were able to effectively kill phagocytosed S. intermedius over a 90-min time course, but there was no significant enhancement of killing by prior incubation of the bacteria with any clinical serum as opposed to normal sera. This suggests that the humoral response to S. intermedius does not affect intracellular killing per se.

Polymorphonuclear neutrophil granulocyte chemotactic hyperresponsiveness in a case of canine acromegaly

Growth hormone (GH) has recently been shown to affect polymorphonuclear neutrophil granulocyte (PMN) function and to be secreted by mononuclear cells, indicating that the hormone may be active in an immunophysiologic network, acting as an endo- or paracrine priming agent. The purpose of the present study was to evaluate the chemotactic responsiveness of canine peripheral PMN in a dog with acromegaly, caused by spontaneous, progesterone-induced hypersecretion of GH and, secondary to this, a seven-fold increase in insulin-like growth factor I (IGF-I). The chemotactic responsiveness towards zymosan-activated serum (ZAS) and leukotriene B4 (LTB4) was evaluated at a time when the dog suffered from acromegaly and again 57 days after corrective surgery (ovariohysterectomy). The experiments showed that PMN from the patient exhibited enhanced chemotactic migration that appeared to be associated with the hypersomatotropic condition as judged from the reversibility of the phenomenon. The glucose intolerance and elevated serum alkaline phosphatase that were observed in the acromegalic dog were also shown to be reversible following surgery.

Impairment of neutrophil functions in a dog with an eosinophilic dermatosis

An eosinophilic dermatosis was diagnosed in a dog with a multifocal distribution of pruritic, pustular and erosive lesions on the trunk. Ectoparasites, fungi and bacteria were not detected in the skin of the dog. At a subsequent admission to the university clinic, bacterial conjunctivitis and superficial pyoderma had developed. At a time when the dog received no medical therapy, evaluation of phagocytosis and chemotactic migration towards a variety of chemotactic factors revealed a general suppression of patient neutrophil responsiveness, as compared to a control dog. Viability of the patient's neutrophils was normal. It was proposed that deactivation of neutrophil functions occurred following exposure to suppressive factors from mast cells, or as a consequence of surface receptor down-regulation due to prolonged cell activation by as yet unknown stimulants. The observed susceptibility to infections in the dog suffering from a primary, sterile eosinophilic dermatosis may be related to impaired host defence against opportunistic microorganisms.