Leukocyte function in Pelger-Huët anomaly of dogs

Immature Neutrophils Released in Acute Inflammation Exhibit Efficient Migration despite Incomplete Segmentation of the Nucleus

Acute inflammation recruits neutrophils with a band-shaped nucleus to the circulation. This neutrophil population was recently shown to have superior antibacterial capacity. Early recruitment of banded neutrophils to an infection site will likely improve the outcome of the immune response, yet it critically depends on efficient migration. However, the current dogma states that the segmentation of the mature neutrophil nucleus has evolved to favor migration through narrow pores as found between endothelial cells and in the interstitium. Therefore, we hypothesized that banded neutrophils migrate less efficiently than neutrophils with segmented nuclei, whereas recently described neutrophils with hypersegmented nuclei would in turn migrate more efficiently. Acute inflammation was evoked in a human model of experimental endotoxemia to recruit neutrophil subsets with different nuclear segmentation to the circulation. To simulate migration toward an infection site, migration of the subsets was studied in in vitro models of transendothelial migration or interstitial chemokinesis and chemotaxis. In both models, nuclear segmentation did not increase migration speed. In dense collagen matrices, the speed of the hypersegmented neutrophils was even reduced compared with the banded neutrophils. Fluorescence microscopy suggested that the hypersegmented neutrophils displayed reduced rear release and deposited more membrane vesicles. Vice versa, migration through narrow pores did not induce nuclear segmentation in the neutrophils. In conclusion, like neutrophils with a segmented nucleus, the banded subset exhibited efficient migration through narrow pores. These findings suggest that the nucleus does not preclude the banded subset from reaching an infection site.

Traps and hyper inflammation - new ways that neutrophils promote or hinder survival

For a long time neutrophil granulocytes were considered simply as terminally differentiated cells with a limited life span and pathogen killing by phagocytosis and chemical toxicity being the sole mode of action. However, work during the last 10 years has started to change this view fundamentally. Modern understanding is that neutrophils have an enormous complexity of functions. This review discusses very recent findings on how neutrophils can control the spread of pathogens and mediate their killing by mechanisms such as formation of DNA nets, how they influence tumour growth and adaptive immune responses and how they manoeuvre inside the diverse compartments of the body. It will also describe how the normally protective functions of neutrophils can have deleterious consequences if they occur in an uncontrolled fashion. These exciting novel findings are likely to completely and permanently change our view of this central leucocyte population.

Pelger-huet anomaly and a mild skeletal phenotype secondary to mutations in LBR

The Lamin B receptor (LBR) gene has been described to encode a bifunctional protein. Mutations in the LBR gene can affect neutrophil segmentation and sterol reductase activity and have been associated with two different recognized clinical conditions, Pelger-Huet anomaly (PHA) and Greenberg skeletal dysplasia. PHA is a benign autosomal co-dominant laminopathy resulting in bilobed neutrophil nuclei in heterozygotes, and unsegmented (ovoid) neutrophil nuclei in homozygotes. Some putative PHA homozygotes have been reported with minor skeletal malformations. Greenberg skeletal dysplasia is a severe autosomal recessive, perinatal lethal dwarfing disorder in which heterozygous carriers are usually without clinical manifestations. We here report a girl who has bilobed neutrophil nuclei and a mild skeletal dysplasia. Mutation analysis showed two novel mutations in the LBR gene: c.651_653 delinsTGATGAGAAA (p.Ile218Aspfs*19) and c.1757G > A (p.Arg586His). These mutations were found to be in trans, and, thus, she is a compound heterozygote. Sterol analysis found trace amounts of cholesta-8,14-dien-3beta-ol, which is normally undetected in healthy individuals. This and previously reported cases suggest that mutations in LBR can result in a continuum of phenotypic manifestations.

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.

Pelger-Huët anomaly in two related mixed-breed dogs

A 6-month-old male mixed-breed dog weighing 12.6 kg weight was presented for evaluation of a subcutaneous nodule on the dorsum. The medical history indicated trimethoprim-sulfamethoxazole treatment 2 months before presentation at the veterinary hospital. The initial complete blood cell count (CBC) results included an apparent left shift. Microscopic examination of a blood smear (Panoptic stain) revealed granulocytes with hyposegmented nuclei, coarse mature chromatin, and a nuclear shape varying from round to bilobed (pince-nez) or slightly indented. Occasional neutrophils and eosinophils had typical segmentation of nuclei. Abnormalities were not present in limited serum biochemical testing. The CBC was repeated 17 and 120 days later, and the results were similar to those observed in the first examination. The parents of the patient were located, and a CBC was performed on both animals. The dam, but not the sire, had nuclear hyposegmentation of granulocytes, confirming the diagnosis of Pelger-Huët anomaly.

Congenital Pelger-Huët anomaly in a Danish/Swedish Farmdog: case report

A 13 year old Danish/Swedish Farmdog from Denmark was evaluated in a veterinary clinic in Warsaw, Poland for evaluation of an orthopedic problem. Radiographs revealed spondylosis and degenerative vertebral disease, which responded to treatment with anti-inflammatory medications. A predominance of hyposegmented neutrophils and eosinophils containing condensed chromatin and normal cytoplasm were identified on a routine CBC. Follow-up blood film evaluations over the course of 12 months confirmed that the hyposegmented granulocytes persisted. The majority of neutrophils contained Grade 2 nuclei (slightly indented), and the mean nuclear score varied from 1.9 to 2.3. Pelger-Huët anomaly (PHA), presumably congenital, was diagnosed based on persistent hyposegmented granulocytes in the absence of an underlying cause for acquired PHA; genetically related dogs were unavailable for testing to confirm vertical transmission. To the authors' knowledge this is the first report of PHA in a Danish/Swedish Farmdog.

The lamin B receptor under transcriptional control of C/EBPepsilon is required for morphological but not functional maturation of neutrophils

The lamin B receptor (LBR) is an integral nuclear envelope protein that interacts with chromatin and has homology to sterol reductases. Mutations in LBR result in Pelger-Huët anomaly and HEM-Greenberg skeletal dysplasia, whereas in mice Lbr mutations result in ichthyosis. To further understand the function of the LBR and its role in disease, we derived a novel mouse model with a gene-trap insertion into the Lbr locus (Lbr(GT/GT)). Phenotypically, the Lbr(GT/GT) mice are similar to ichthyosis mice. The Lbr(GT/GT) granulocytes lack a mature segmented nucleus and have a block in late maturation. Despite these changes in nuclear morphology, the innate granulocyte immune function in the killing of Staphylococcus aureus bacteria appears to be intact. Granulocyte differentiation requires the transcription factor C/EBPepsilon. We identified C/EBPepsilon binding sites within the Lbr promoter and used EMSAs and luciferase assays to show that Lbr is transcriptionally regulated by C/EBPepsilon. Our findings indicate that the Lbr(GT/GT) mice are a model for Pelger-Huët anomaly and that Lbr, under transcriptional regulation of C/EBPepsilon, is necessary for morphological but not necessarily functional granulocyte maturation.

Pelger-Huët anomaly in an Arabian horse

A 9-year-old Arabian mare was evaluated for a 7-day history of malaise. Results of a CBC included a leukocyte concentration within the reference interval (8.4 x 10(3)/microL, reference interval 6.0-14.0 x 10(3)/microL) with an apparent degenerative left shift (segmented neutrophils 1.2 x 10(3)/microL, reference interval 2.5-7.5 x 10(3)/microL; hyposegmented neutrophils 1.8 x 10(3)/microL, reference interval 0.0-0.2 x 10(3)/microL). Serum clinical chemistry results included increased aspartate transaminase, alkaline phosphatase, and gamma-glutamyltransferase activities. A presumptive diagnosis of hepatitis or cholangiohepatitis was made. The horse was treated with antimicrobials and the malaise quickly resolved. However, in a recheck CBC on day 13, the apparent degenerative left shift remained. Further evaluation of the blood smear revealed many hyposegmented granulocytes with coarse mature chromatin and normal cytoplasmic features. On the basis of the microscopic examination, the horse was diagnosed with Pelger-Huët anomaly. The patient's offspring was subsequently also diagnosed with Pelger-Huët anomaly on the basis of blood film examination. Neutrophil, eosinophil, and basophil mean nuclear scores in both affected horses (mare, range 1.5-2.6; offspring, range 1.6-3.2) were lower than those in 2 unrelated Arabian horses (range, 2.8-5.0) and 5 non-Arabian control horses (range, 2.8-5.0). Results of immunophenotyping and phagocytosis/oxidative burst assays via flow cytometry showed no difference in the expression of myeloid-specific or adhesion molecules or in neutrophil function between affected and control horses. This is the second known report of equine Pelger-Huët anomaly, both of which affected Arabian horses.

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.

Heterophil function in healthy chickens and in chickens with experimentally induced staphylococcal tenosynovitis

Heterophil function was evaluated in 16 healthy chickens and in 46 chickens with experimentally induced staphylococcal tenosynovitis. In paired blood samples, heterophils from chickens with tenosynovitis had a significant increase in adherence, chemotaxis, phagocytosis, and bacterial killing of Staphylococcus aureus compared to heterophils from healthy chickens. The percent adherence of heterophils to nylon fiber columns increased significantly from a 78.4% mean +/- 6.6% standard deviation to 87.6% +/- 3.2% after induction of staphylococcal tenosynovitis. Heterophil movement following in vitro exposure to saline or endotoxin was increased in chickens with tenosynovitis; 3 +/- 1 heterophils/0.25 mm2 to 10 +/- 6 heterophils/0.25 mm2 and 136 +/- 29 heterophils/0.25 mm2 to 340 +/- 74 heterophils/0.25 mm2, respectively. Endotoxin-activated serum was chemoattractive for heterophils from all chickens. Flow cytometry was used to define the heterophil population on light scatter histograms, evaluate individual cell phagocytosis of latex beads, and quantitate the number of beads phagocytosed per heterophil. When incubated with increased numbers of beads, only heterophils from chickens with tenosynovitis phagocytosed higher numbers of beads. At heterophil to bead ratios of 1:10, the percentage of heterophils that phagocytosed beads increased from baseline values of 37.8% +/- 9.0% to post-infection values of 67.3% +/- 7.5%. Using 1:20 heterophil to bead ratios, heterophil phagocytosis increased from 38.7% +/- 9.9% to post-infection values of 79.8% +/- 7.3%. Heterophils from all chickens were able to phagocytose and kill log phase staphylococcal bacteria. After phagocytosis, the heterophils from chickens with staphylococcal tenosynovitis rapidly decreased the number of viable bacterial colony forming-units per milliliter by approximately one log.(ABSTRACT TRUNCATED AT 250 WORDS)

A rapid microassay for measuring the luminol-dependent chemiluminescent response in canine whole blood

A microassay for the luminol-dependent chemiluminescence (CL) response in canine whole blood was developed to measure indirectly the oxidative metabolism of peripheral blood leukocytes. Fifty microliters of blood were mixed with 705 microliters of Hank's balanced salt solution containing 25 mM Hepes and 1.3 x 10(-4) M luminol. This mixture was allowed to equilibrate for 5 min after which 60 microliters of latex beads (0.801 microns diameter) were added as a stimulant, and the CL response was monitored continuously for 5 min at 37 degrees C using a luminometer. The whole blood CL response was significantly correlated (r = 0.784, P less than 0.01, n = 14) with the number of neutrophils in the peripheral blood. Further, the whole blood CL response was abolished by the depletion of neutrophils after passing the blood through an adherence column and by the addition of sodium azide. The relative chemiluminescent light unit (RCLU) was a reliable marker for comparing each peak value in different samples. The coefficient of variation (CV) of repetitive samples was 9.87%, and the CV of 14 normal dogs was 15.7%. This method is useful and applicable for screening the CL response in canine whole blood.

Neutrophil adherence, phagocytic-nitroblue tetrazolium reduction and chemiluminescence in canine whole blood

Methods for measuring neutrophil adherence, phagocytic-nitroblue tetrazolium (NBT) reducing activity and chemiluminescence were applied to canine whole blood as means for routine assessment of neutrophil functions. The phagocytic-NBT reduction test appeared to be useful for monitoring the NBT reducing activity of phagocytic cells associated with phagocytic functions. Ethylene diamine tetraacetic acid suppressed both the adherence and the phagocytic-NBT reducing activity of neutrophils. Increased phagocytic-NBT reduction and an enhanced chemiluminescence response were observed in dogs with neutrophilia. These methods provide a rapid and practical screening procedure for measuring selected phagocytic functions in canine whole blood.

Clinical interpretation of leukocyte responses

Basic information has been presented concerning leukocyte (neutrophil, monocyte, lymphocyte, eosinophil, and basophil) function, production, kinetics, and response to various physiological and disease states. Using this information, veterinary practitioners should be able to interpret leukogram data from sick and healthy dogs and cats. Specifically, characteristic leukogram patterns such as physiological leukocytosis, corticosteroid-associated changes, and the presence of infection or severe inflammation should be recognized. In addition, interpretation of individual leukocyte responses should be possible. Several tables have been provided to assist in constructing a differential diagnosis to explain increases or decreases in absolute leukocyte numbers that lie outside of expected reference intervals.