Leukocyte dysfunction in the bovine homologue of the Chediak-Higashi syndrome of humans

Neutrophil function in small animals

Neutrophils are highly mobile phagocytes that serve as the initial effectors against pathogens and are actively recruited to sites of inflammation. Chemoattractants guide them toward the inflammation, and their interaction with endothelial cells directs them through postcapillary venules and into the tissues. Once they have reached their destination, they can efficiently kill many microbes via phagocytosis, extracellular release of granule contents, and the formation of NETs. They also actively produce cytokines and other mediators to promote or suppress inflammation, repair tissues, and modulate the immune response. The importance of neutrophil function in host health is emphasized through discussion of inherited disorders of neutrophil function such as leukocyte adhesion deficiency and cyclic hematopoiesis.

Effects of human IL-8 isoforms on bovine neutrophil function in vitro

Interleukin 8 (IL-8) is a potent chemotactic and activating agent for human neutrophils and bovine IL-8 is chemotactic for bovine neutrophils; however, it is unclear whether IL-8 activates bovine neutrophils. Two isoforms of human recombinant (hr) IL-8 protein (77 and 72 amino acid) were used to stimulate bovine neutrophils in vitro. Bovine neutrophils exhibited significant migration in the presence of 0.1, 0.5, 1.0 and 5.0ngml(-1) hr IL-8 when incubated for 30min at 37 degrees C in a modified Boyden chamber assay. Both the 77 and 72 aa forms were equally effective in inducing migration in this assay. At the highest doses of IL-8 examined (1 and 5ngml(-1)), migration was similar to migration in the presence of 20% zymosan-activated serum (ZAS) or 12h lipopolysaccharide (LPS)-stimulated blood monocyte supernatants (CM). Significant (p<0. 05) release of alkaline phosphatase (ALK-P) (from specific granules) occurred but myeloperoxidase (MPO) release and superoxide anion production were not enhanced in bovine neutrophils by either form of hrIL-8 at any of the doses tested. Significant (p<0.05) alkaline phosphatase release was observed in the presence of 10 and 100ngml(-1) for the 72 aa form of IL-8 and only at the higher dose for the 77 aa form of IL-8. The ZAS and CM significantly enhanced neutrophil degranulation of ALK-P and MPO as well as inducing superoxide anion production. These results suggest that IL-8 may play a role in both neutrophil recruitment and activation during bovine inflammatory processes.

Cell-surface lactoferrin as a marker for degranulation of specific granules in bovine neutrophils

OBJECTIVE

To develop a rapid and accurate flow cytometric method for measuring degranulation of specific granules in bovine neutrophils.

SAMPLE POPULATION

Blood samples obtained from four 6- to 18-month-old Holstein cattle.

PROCEDURE

A monoclonal antibody (BL97) was generated against bovine lactoferrin and tested for applicability in ELISA, immunoprecipitation tests, immunofluorescence microscopy, and flow cytometric analyses. Using this antibody, cell-surface lactoferrin was measured concurrent with amount of secreted lactoferrin from bovine neutrophils activated with phorbol myristate acetate (PMA). Cell-surface lactoferrin also was measured on neutrophils in bovine whole blood stimulated with PMA, platelet-activating factor (PAF), N-formyl-methionyl-leucyl-phenylalanine (fMLF), and interleukin 8 (IL-8).

RESULTS

Antibody BL97 recognized bovine lactoferrin in ELISA and western immunoblots and was useful for immunoprecipitation testing, immunofluorescence microscopy, and flow cytometric analyses of bovine leukocytes. Neutrophils activated with PMA had parallel increases in content of secreted lactoferrin (measured by ELISA) and cell-surface lactoferrin (measured by flow cytometry) with increasing PMA concentrations. In addition, fluorescein-conjugated BL97 antibody detected increases in cell-surface lactoferrin on neutrophils in bovine whole blood after activation with PMA, PAF, and IL-8. In contrast, increases in cell-surface lactoferrin were not detected on bovine neutrophils treated with fMLF.

CONCLUSION AND CLINICAL RELEVANCE

Measurement of cell-surface lactoferrin on bovine neutrophils by flow cytometry is a valid and rapid method for assessment of release of lactoferrin from specific granules in these cells and represents a means to rapidly measure neutrophil activation. This technique allows for investigation of mechanisms of neutrophil modification in isolated cells as well as in whole blood.

Isolation of bovine neutrophils with biomagnetic beads: comparison with standard Percoll density gradient isolation methods

A prerequisite for studies on bovine neutrophils is a reliable method of neutrophil isolation from blood to obtain highly purified cell populations that are functionally active. Since current techniques of neutrophil isolation fall short of these requirements, we have developed a newer and more effective technique for isolation of bovine neutrophils that utilizes biomagnetic beads coated with a monoclonal antibody that recognizes an abundant surface antigen on bovine neutrophils to purify these cells. Comparison of the purity and viability of bovine neutrophils isolated by a conventional method (continuous Percoll density gradient) with this new method showed that neutrophils isolated with biomagnetic beads were higher in purity and had an increased yield. In addition, cells isolated with biomagnetic beads demonstrated normal or even improved function in assays of chemotaxis, phagocytosis, degranulation, and respiratory burst activity. Finally, bovine neutrophils isolated using this method showed an overall lower level of spontaneous apoptosis, which correlates well with the high level of viability observed in the purified cell preparations. Thus, this method represents a significant advance over current methods for isolating bovine neutrophils and would be widely applicable to labs studying the biochemistry and signal transduction pathways in these cells.

Defective in vitro motility of polymorphonuclear leukocytes of homozygote and heterozygote Chediak-Higashi cats

The in vitro migratory responses of neutrophils of homozygote and heterozygote Chediak-Higashi cats were defective in an under-agarose assay when compared to the behavior of phagocytes of control cats. The linear distances traversed by the leading front of migrating Chediak-Higashi neutrophils toward streptococcal culture supernatant, zymosan-activated serum or buffer were reduced and smaller numbers of Chediak-Higashi phagocytes populated the resulting migration areas than did cells of control animals. The relative migration parameters of the Chediak-Higashi phagocytes, however, did not differ from the corresponding parameters of control neutrophils in the presence of streptococcal culture supernatant. Therefore, phagocytes of homozygote and heterozygote Chediak-Higashi cats recognized and responded equally well to the bacterial stimuli as did cells of control animals but traveled shorter distances primarily because of a reduced inherent motility. Similar results were also obtained when the feline phagocytes were attracted by zymosan-activated serum. In addition the relative migration parameters of the neutrophils of homozygote Chediak-Higashi cats were reduced and the normalized spatial distributions of their migrating cells were significantly different in the presence of 100% and 20% zymosan-activated serum when compared to the corresponding migration parameters of carrier and control animals. Defective recognition or responses to the higher concentrations of these host-derived attractants complicated, therefore, the already reduced inherent motility of the phagocytes of homozygote Chediak-Higashi cats.

A colorimetric assay for quantitating bovine neutrophil bactericidal activity

A colorimetric assay was developed for quantitating bovine neutrophil bactericidal activity against Staphylococcus aureus. The procedure used the tetrazolium compound, 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT). The assay was conducted by incubating antibody-opsonized S. aureus with neutrophils in microtiter plates for 1 h at a ratio of 10 bacteria per neutrophil. Neutrophils were then lysed with saponin. The MTT was added and samples were incubated for 10 min. Live S. aureus reduced MTT to purple formazan. Dead bacteria and lysed neutrophils did not react with MTT. Bacterially-reduced formazan was solubilized by adding isopropanol and formazan production was quantitated by measuring absorption at 560 nm. Absorption of formazan was directly related to viable bacteria cell number and was used to determine the number of S. aureus not killed by neutrophils. The percentage of bacteria killed by neutrophils was determined by extrapolation from a standard formazan curve that was derived by incubating MTT with known numbers of S. aureus. The colorimetric MTT assay detected suppressed bactericidal activity after in vitro treatment of bovine neutrophils with colchicine, cytochalasin B, or phorbol 12-myristate 13-acetate. In vitro treatment of neutrophils with low levels of recombinant bovine interferon gamma (rBoIFN-gamma) enhanced bactericidal activity, whereas high levels decreased activity. These results suggest the colorimetric MTT bactericidal assay is efficacious in detecting modulation of bovine neutrophil bactericidal activity. Furthermore, the MTT assay has many advantages over traditional bactericidal assays in that it is sensitive, inexpensive, requires less than 3 h to complete, and can analyze many neutrophil samples in a single day.

Effect of muramyl dipeptide analog on Salmonella enteritidis infection in beige mice with Chediak-Higashi syndrome

Beige mutant (bg/bg) mice with Chediak-Higashi syndrome (CHS) were much more sensitive to virulent Salmonella enteritidis No. 11 strain than parental C57 BL/6 (+/+) or heterozygous (bg/+) mice, and they had weaker bactericidal activity against the organisms. Muramyl dipeptide (MDP) and N alpha-(N-acetyl-muramyl-L-alanyl-D-isoglutamyl)-N epsilon-stearoyl-L-lysine [MDP-Lys(L18)], a synthetic derivative of MDP, failed to confer any protection against the infection, but the MDPs showed some ability to stimulate the bactericidal activity in the peritoneal cavities and spleens of these mice. The bactericidal effect of MDP-Lys(L18) was dose-dependent, and the greatest effect was seen when it had been injected 24 hr before the infection. Multiple injections of MDP were much more beneficial than a single injection. Previous injection of N2,O2'-dibutyryl guanosine 3' : 5'-cyclic monophosphate (DB-cGMP) improved the impaired bactericidal capacity in beige mice, but the simultaneous injection of N6,O2-dibutyryl adenosine 3' : 5'-cyclic monophosphate (DB-cAMP) with DB-cGMP abolished the effect of DB-cGMP. The augmentation of bactericidal capacity by MDP-Lys(L18) was not affected by the injection of either DB-cGMP or DB-cAMP, suggesting that the effect of the MDPs was not related directly to cyclic nucleotide regulation in beige mice.

Delayed-type skin hypersensitivity and in vitro lymphocyte immunostimulation responses of swine following inoculation with Mycobacterium avium cell walls and a mycobacterial immunopotentiating glycolipid

Miniature swine (n = 5 per group) were inoculated intradermally with mineral oil-in-water emulsions containing either 150 micrograms of mycobacterial immunopotentiating glycolipid P3 (EP3), 150 micrograms of lyophilized Mycobacterium avium (serotype 8) cell walls (E-MaCW), or 150 micrograms P3 and 150 micrograms M. avium cell walls (EP3-MaCW). Swine vaccinated with E-MaCW and EP3-MaCW developed antigen-sensitive lymphocytes detectable with delayed-type hypersensitivity (DTH) skin tests and lymphocyte transformation assays. Swine injected with EP3 were not sensitized. In general EP3-MaCW evoked a more pronounced in vivo DTH tuberculin skin test and in vitro lymphocyte transformation responses than E-MaCW. Time-course studies indicated a more persistent response in swine injected with EP3-MaCW than in those given E-MaCW. Commercial type Yorkshire swine (n = 5) inoculated intradermally with EP3-MaCW developed cell-mediated immune (CMI) responses to avian tuberculin detectable in vivo with delayed-type skin hypersensitivity and in vitro with lymphocyte immunostimulation responses.

Canine granulocytopathy syndrome: an inherited disorder of leukocyte function

A disease closely resembling the human neutrophil dysfunction syndromes has been identified in a colony of dogs. The syndrome, referred to as the canine granulocytopathy syndrome, is characterized by recurrent-life-threatening bacterial infections and a greatly shortened life span. The disease is genetically determined, being transmitted as an autosomal recessive trait. The increased susceptibity to pyogenic infections and shortened life span is related to an impairment of leukocyte function at the cellular level. Preparation of neutrophils from affected animals exhibit impaired in vitro killing of Esherichia coli. The defect in bactericidal activity is associated with reduced glucose oxidation by the hexose monophosphate shunt and an increase capacity to reduce nitroblue tetrazolium dye. The data obtained thus far indicate the canine granulocytopathy syndrome will be of considerable value as a model for study of granulocytypathy sydromes in man.

Interaction of polymorphonuclear leukocytes with smooth and rough strains of Brucella abortus

The bactericidal activity of guinea pig and human polymorphonuclear leukocytes (PMNs) against a smooth-intermediate strain (45/0) and a rough strain (45/20) of Brucella abortus has been examined. After incubation for 120 min, guinea pig PMNs incubated with either the smooth strain 45/0 or the rough strain 45/20 exhibited no bactericidal activity against the former and caused only a 34% decrease in viability of the latter. Human PMNs were more bactericidal than guinea pig PMNs to both strains; however, the killing of strain 45/20 by human PMNs was less than that observed in control experiments with S. aureus strain 502A. Both strains of B. abortus readily associated with guinea pig and human PMNs, and the bacteria were apparently ingested without stimulation of the hexose monophosphate pathway. Lysates (10 micrograms/ml, pH 5.5), prepared from guinea pig or human granules, were not particularly toxic to either strain unless supplemented with H2O2 and a halide (I- or Cl-). An oxygen-dependent killing system appeared to be lethal against both strains of B. abortus, with I- being more active than Cl- in the presence of H2O2 and granule lysate. The data suggest that degranulation after ingestion of Brucella by phagocytes does not occur due to the lack of a proper stimulus or possibly the baccilli actively inhibit the degranulation process thereby protecting the microbe from killing systems normally effective against extracellular parasites.

Eosinophil and neutrophil granulocyte exudation in the Chediak-Higashi (beige) mouse

Humans with Chediak-Higashi syndrome (CHS) and mice carrying the beige mutation have a heritable defect which results in the presence of giant inclusion granules in the cytoplasm in a wide variety of cells and a markedly increased susceptibility to infections. To test whether this increased susceptibility to infection might be a consequence of impaired accumulation of granulocytes at sites of inflammatory-immune stimulation, we quantitated the exudation of granulocytes into the peritoneum in response to secondary tetanus toxoid challenge in normal mice and in two inbred mouse strains with the beige mutation. Neutrophil and eosinophil granulocyte responses in the peritoneal cavity were not diminished in the beige mice as compared to normal mice when previously sensitized animals were challenged intraperitoneally with tetanus toxoid. Since accumulation of cells at the in vivo site of inflammatory immune stimulation did not seem impaired in the mutant beige mice, it would appear that their increased susceptibility to infections is not due to impairment of cellular exudative responses, including the immune components of the eosinophil response.

The Chediak-Higashi (beige) mutation in two mouse strains. Allelism and similarity in lysosomal dysfunction

A mutation called beige, with a phenotype similar to that of the human Chediak-Higashi syndrome, has occurred independently in two inbred strains of mice. Beige-J (bgj) occurred as a spontaneous mutation in the C57B1/6J strain and beige (bg) was radiation-induced in mice of heterogenous background which were then inbred as strain SB/Le (bg/bg), the subject of the present study. As in the previously characterized C57Bl/6J beige-J mutant, there is a correlation between abnormal lysosome structure and defective lysosome function in SB/Le beige mice. They secrete much less than normal amounts of lysosomal enzymes from proximal tubule cells and, hence, have increased lysosomal enzyme activity in kidney. In addition, after treatment of either beige strain with androgen, numerous giant beta-glucuronidase-containing lysosomes are present in kidney proximal tubule cells near the corticomedullary border. By directly measuring the rate of beta-glucuronidase synthesis in androgen-treated SB/Le beige mouse kidney, it was shown that the greater accumulation of this lysosomal enzyme in proximal tubule cells was not due to an increase in its rate of synthesis. Genetic analysis of the beige mutations in the two mutant strains demonstrated that both mutant genes are recessive and, in fact, are allelic. The results suggest that both beige strains are defective in intracellular motility of lysosomes and/or their fusion with cellular membranes, and that both mutant strains are suitable experimental models for the human Chediak-Higashi syndrome.