Exercise induced mobilisation of the marginated granulocyte pool in the investigation of ethnic neutropenia

Clozapine-specific proliferative response of peripheral blood-derived mononuclear cells in Japanese patients with clozapine-induced agranulocytosis

BACKGROUND

Although clozapine-induced granulocytopenia (CIG) is less severe than clozapine-induced agranulocytosis (CIA), and some patients with CIG may not go on to develop serious complications, clozapine is discontinued in cases of both CIA and CIG. Understanding the pathogenic mechanisms of CIA/CIG could provide better management of clozapine therapy. Recently, as a mechanistic insight into adaptive immune systems, European groups reported clozapine-specific proliferative responses and clozapine-specific T cells using blood taken from patients with CIA and/or CIG.

AIMS

The aims of our study are to support this mechanistic evidence and to investigate the difference in the lymphocyte response to clozapine between patients with CIG and those with CIA.

METHODS

Lymphocyte stimulation tests (LSTs) were conducted using CD25-positive cell-depleted peripheral blood-derived mononuclear cells (PBMCs) isolated from blood of four Japanese patients with CIA, four patients with CIG, and nine clozapine-tolerant subjects.

RESULTS

Three of four patients with CIA and one of four patients with CIG showed proliferative responses to clozapine with a stimulation index of greater than 2. In contrast, none of the nine clozapine-tolerant subjects showed any response to clozapine. Olanzapine did not stimulate PBMCs of patients with CIA, patients with CIG, or clozapine-tolerant subjects.

CONCLUSIONS

Clozapine- and CIA-specific lymphocyte reactions in a Japanese population provided supportive evidence that the pathogenesis of CIA is based on adaptive immune reactions. In addition, patients with CIG who show a positive response to an LST may at the very least not be chosen for clozapine-rechallenge and further prospective studies are desirable to verify this hypothesis.

Chronic neutropenia: how best to assess severity and approach management?

INTRODUCTION

Neutropenia is a relatively common finding in medical practice and the medical approach requires a gradual and pertinent diagnostic procedure as well as adapted management.

AREAS COVERED

The area of chronic neutropenia remains fragmented between diverse diseases or situations. Here physicians involved in different aspects of chronic neutropenia gather both the data from medical literature till the end of May 2021 and their experience to offer a global approach for the diagnosis of chronic neutropenia as well as their medical care.

EXPERT OPINION

In most cases, the neutropenia is transient, frequently related to a viral infection, and not harmful. However, neutropenia can be chronic (i.e. >3 months) and related to a number of etiologies, some clinically benign, such as so-called 'ethnic' neutropenia. Autoimmune neutropenia is the common form in young children, whereas idiopathic/immune neutropenia is a frequent etiology in young females. Inherited neutropenia (or congenital neutropenia) is exceptional, with approximately 30 new cases per 10⁶ births and 30 known subtypes. Such patients have a high risk of invasive bacterial infections, and oral infections. Supportive therapy, which is primarily based on daily administration of an antibiotic prophylaxis and/or treatment with granulocyte-colony stimulating factor (G-CSF), contributes to avoiding recurrent infections.

Imaging of muscle activity-induced morphometric changes in fibril network of myofascia by two-photon microscopy

Myofascia, deep fascia enveloping skeletal muscles, consists of abundant collagen and elastin fibres that play a key role in the transmission of muscular forces. However, understanding of biomechanical dynamics in myofascia remains very limited due to less quantitative and relevant approaches for in vivo examination. The purpose of this study was to evaluate the myofascial fibril structure by means of a quantitative approach using two-photon microscopy (TPM) imaging in combination with intravital staining of Evans blue dye (EBD), a far-red fluorescence dye, which potentially labels elastin. With focus on myofascia of the tibial anterior (TA) muscle, the fibril structure intravitally stained with EBD was observed at the depth level of collagen fibrous membrane above the muscle belly. The EBD-labelled fibril structure and orientation in myofascia indicated biomechanical responses to muscle activity and ageing. The orientation histograms of EBD-labelled fibrils were significantly modified depending upon the intensity of muscle activity and ageing. Moreover, the density of EBD-labelled fibrils in myofascia decreased with habitual exercise but increased with muscle immobilization or ageing. In particular, the diameter of EBD-labelled fibrils in aged mice was significantly higher. The orientation histograms of EBD-labelled fibrils after habitual exercise, muscle immobilization and ageing showed significant differences compared to control. Indeed, the histograms in bilateral TA myofascia of exercise mice made simple waveforms without multiple sharp peaks, whilst muscular immobilization or ageing significantly shifted a histogram with sustaining multiple sharp peaks. Therefore, the dynamics of fibre network with EBD fluorescence in response to the biomechanical environment possibly indicate functional tissue adaptation in myofascia. Furthermore, on the basis of the knowledge that neutrophil recruitment occurs locally in working muscles, we suggested the unique reconstruction mechanism involving neutrophilic elastase in the myofascial fibril structure. In addition to the elastolytic susceptibility of EBD-labelled fibrils, distinct immunoreactivities and activities of neutrophil elastase in the myofascia were observed after electric pulse stimulation-induced muscle contraction for 15 min. Our findings of EBD-labelled fibril dynamics in myofascia through quantitative approach using TPM imaging and intravital fluorescence labelling potentially brings new insights to examine muscle physiology and pathology.

Isolated Neutropenia/Benign Ethnic Neutropenia: A Common Clinical and Laboratory Finding in Southern and Western Saudi Arabia

OBJECTIVE

Isolated mild neutropenia is a common clinical problem in some ethnicities including Arabs and Middle Eastern population. The current study aims to authenticate the prevalence of isolated neutropenia in Southern and Southwestern Saudi Arabia, explore the effect of altitude or regional differences and to suggest a new reference range for neutrophil count.

METHODS

In this retrospective cross-sectional study, laboratory results of a commercial laboratory were screened over a period of 5 years (2016-2020) in seven different cities of different altitudes in South and southwestern Saudi Arabia. Participants' laboratory investigations were reviewed and excluded for any abnormal complete blood count, renal profile, liver profile, lipid profile, thyroid function test, fasting blood glucose, or HbA1c findings. Descriptive analysis and 95th percentile range were calculated using standard statistical methods.

RESULTS

A total of 91,880 complete blood count results were included in the final analysis. Isolated neutropenia was common laboratory finding, with a prevalence ranging from 11% to 23%. The 2.5th percentile of the neutrophil count was lower than currently utilized 1.5×109/L in all studied seven cities.

CONCLUSION

Mild to moderate neutropenia is common in Southern and Southwestern Saudi Arabia. Benign ethnic neutropenia (BEN) likely explains this high prevalence. Since BEN has no clinical significance, the reference range for normal neutrophil counts needs to be adjusted to reflect the effect of BEN.

Haematological values in a healthy adult population in Yaoundé, Cameroon

Background

Haematological values derived from local populations are useful in laboratories to improve diagnoses for local patients. In Cameroon, these data are not yet available. Moreover, there is great variation in baseline parameters pertaining to full blood cell count among medical laboratories.

Objectives

This study aimed to determine values for the complete blood cell count of a healthy adult Cameroonian population for use in locally derived ranges in our medical laboratories.

Methods

A cross-sectional study was conducted among blood donors attending three blood banks in Yaoundé from November 2015 to September 2016. We expected to obtain at least 120 venous blood samples from both men and women. Tests were performed for (1) HIV, (2) complete blood cell count, (3) hepatitis B virus, (4) malaria, (5) syphilis, (6) C-reactive protein and (7) hepatitis C virus.

Results

We enrolled 294 healthy participants (161 men, 133 women) aged 18 to 55 years. The median haemoglobin concentration was 135 g/L in men and 114 g/L in women (p < 0.001). The median reticulocyte count was 60 × 10⁹/L in men and 40 × 10⁹/L in women (p < 0.001). Significant variation by sex was observed for the platelet count. The median white blood cell count was 4.1 × 10⁹/L in men and 4.6 × 10⁹/L in women (p = 0.008).

Conclusion

This study provides locally derived ranges for complete blood cell and reticulocyte counts for a healthy adult population in Yaoundé, Cameroon. These results can be used pending larger studies.

Benign ethnic neutropenia

Benign ethnic neutropenia (BEN) is one of the most common causes of chronic neutropenia seen in individuals of African, Middle Eastern and West Indian descent, affecting many individuals worldwide. Despite its prevalence, many physicians are not familiar with this benign condition, resulting in unnecessary evaluation and testing for neutropenia in otherwise healthy individuals. Clinically, patients with BEN are at no increased risk of infection despite their neutropenia. Implications of this condition are highlighted in those patients receiving therapies that have a known side effect of neutropenia, most commonly chemotherapy agents. Studies have suggested that disparities in survival among those patients receiving chemotherapy between patients of European decent and African decent may be attributed to measured neutropenia in these populations, questioning whether BEN could be an influential factor. This review encompasses all aspects of benign ethnic neutropenia, providing information about this condition and helping to guide clinical decision-making as to when an aggressive work up and referral are indicated and when it is appropriate to monitor. Additionally, we review the role of genetic studies in identifying the genes related to BEN, summarize the theories that offer the most accepted mechanisms behind the condition, and address the importance of pursuing larger studies to assess the implication of BEN in oncology patients as well as patients taking neutropenia-causing medications.

The Duffy antigen receptor for chemokines, ACKR1,- 'Jeanne DARC' of benign neutropenia

Benign neutropenia, observed in different ethnic groups, is the most common form of neutropenia worldwide. A specific single nucleotide polymorphism, rs2814778, located at the promoter of the ACKR1 (previously termed DARC) gene, which disrupts a binding site for the GATA1 erythroid transcription factor, resulting in a ACKR1-null phenotype, was found to serve as a predictor of low white blood cell and neutrophil counts in African-Americans and Yemenite Jews. Individuals with benign neutropenia due to the ACKR1-null allele have been found to have an increased susceptibility to human immunodeficiency virus infection and, on the other hand, a protective effect against malaria. The associated protective effect may explain the spread of the ACKR1-null allele by natural selection. The reviewed relationships between ACKR1 polymorphism and various pathological states may have important clinical implications to individuals with and without benign neutropenia. Potential mechanisms for ACKR1 (previously termed DARC) modulation during neutrophil recruitment to inflammation, and chemokine bioavailability in the circulation and in local tissue are reviewed and discussed.

Neutrophil phenotypes in health and disease

Neutrophils are one of the most important effector cells of the innate immune response (1). They are traditionally seen as a homogenous population of short-lived cells mainly involved in the defence against extracellular microorganisms by phagocytosis and intracellular killing (1,2). The cells contain a large armamentarium that aids in this function and ranges from the production of reactive oxygen species by a membrane-bound NADPH oxidase to cytotoxic proteins and peptides residing in the different granules present in the cytoplasm (3). Recently, the view of neutrophils belonging to a homogenous population of cells has been challenged, and several neutrophil phenotypes have been described that exhibit specialized functions, such as involvement in tissue repair, tumour killing and immune regulation (4). It is not clear whether these cells belong to separate parallel lineages originating from the bone marrow or that neutrophils become instructed in the distant tissues, thus changing their phenotypes. In addition, functional heterogeneity in a phenotypically homogenous population of neutrophils adds to the complexity of neutrophil phenotypes(5). This article will review the current literature describing the heterogeneity within the neutrophil compartment with respect to both phenotype and function in health and disease.

Effect of circadian variation on neutrophil mobilization to the peripheral blood in benign constitutional neutropenia

Benign constitutional neutropenia (BCN) is an asymptomatic condition characterized by mild chronic neutropenia in patients with no history of recurrent infections. Most patients are referred for further testing, increasing health care costs. We present an alternative form of assessment of individuals with BCN based on neutrophil circadian variation. The objective of this study was to evaluate whether circadian variations of neutrophil counts would result in neutrophil values higher than neutropenia threshold in individuals with BCN. Absolute neutrophil counts (ANCs) were evaluated in 102 patients with BCN (<1500 cells/μL) and 60 age- and sex-matched controls. Paired blood counts were performed in the early morning and in the early afternoon. We observed a significant difference between morning and afternoon ANC in BCN patients (879 cells/μL, 95% CI 745-1028, p < 0.001), as well as in the controls (619 cells/μL, 95% CI 443-796, p < 0.001). The ANC increase between the two evaluations was significantly greater in BCN patients compared with controls: 83% and 27%, respectively (p < 0.001). The ANC increment was higher in the groups with a lower morning ANC: 105%, 63%, and 27% in the <1000, 1000-1500, and >1500 cells/μL groups, respectively (p < 0.001). Of all BCN patients, 73% presented with >1500 cells/μL in the afternoon and 16% improved from the <1000 cells/μL to the 1000-1500 cells/μL category. In conclusion, neutrophil circadian variation measurement allows many BCN patients to be excluded from the neutropenia threshold. We identified a simple, easy, and feasible way to assess neutrophil reserve in patients with BCN with a potential reduction in costs of the assessment.

Pharmacogenomic Study of Clozapine-Induced Agranulocytosis/Granulocytopenia in a Japanese Population

BACKGROUND

Clozapine-induced agranulocytosis (CIA)/clozapine-induced granulocytopenia (CIG) (CIAG) is a life-threatening event for schizophrenic subjects treated with clozapine.

METHODS

To examine the genetic factor for CIAG, a genome-wide pharmacogenomic analysis was conducted using 50 subjects with CIAG and 2905 control subjects.

RESULTS

We identified a significant association in the human leukocyte antigen (HLA) region (rs1800625, p = 3.46 × 10(-9), odds ratio [OR] = 3.8); therefore, subsequent HLA typing was performed. We detected a significant association of HLA-B*59:01 with CIAG (p = 3.81 × 10(-8), OR = 10.7) and confirmed this association by comparing with an independent clozapine-tolerant control group (n = 380, p = 2.97 × 10(-5), OR = 6.3). As we observed that the OR of CIA (OR: 9.3~15.8) was approximately double that in CIG (OR: 4.4~7.4), we hypothesized that the CIG subjects were a mixed population of those who potentially would develop CIA and those who would not develop CIA (non-CIA). This hypothesis allowed the proportion of the CIG who were non-CIA to be calculated, enabling us to estimate the positive predictive value of the nonrisk allele on non-CIA in CIG subjects. Assuming this model, we estimated that 1) ~50% of CIG subjects would be non-CIA; and 2) ~60% of the CIG subjects without the risk allele would be non-CIA and therefore not expected to develop CIA.

CONCLUSIONS

Our results suggest that HLA-B*59:01 is a risk factor for CIAG in the Japanese population. Furthermore, if our model is true, the results suggest that rechallenging certain CIG subjects with clozapine may not be always contraindicated.

The effect of a selective CXCR2 antagonist (AZD5069) on human blood neutrophil count and innate immune functions

AIMS

The aim of the present study was to investigate whether selective antagonism of the cysteine-X-cysteine chemokine receptor-2 (CXCR2) receptor has any adverse effects on the key innate effector functions of human neutrophils for defence against microbial pathogens.

METHODS

In a double-blind, crossover study, 30 healthy volunteers were randomized to treatment with the CXCR2 antagonist AZD5069 (100 mg) or placebo, twice daily orally for 6 days. The peripheral blood neutrophil count was assessed at baseline, daily during treatment and in response to exercise challenge and subcutaneous injection of granulocyte-colony stimulating factor (G-CSF). Neutrophil function was evaluated by phagocytosis of Escherichia coli and by the oxidative burst response to E. coli.

RESULTS

AZD5069 treatment reversibly reduced circulating neutrophil count from baseline by a mean [standard deviation (SD)] of -1.67 (0.67) ×10(9) l(-1) vs. 0.19 (0.78) ×10(9) l(-1) for placebo on day 2, returning to baseline by day 7 after the last dose. Despite low counts on day 4, a 10-min exercise challenge increased absolute blood neutrophil count, but the effect with AZD5069 was smaller and not sustained, compared with placebo treatment. Subcutaneous G-CSF on day 5 caused a substantial increase in blood neutrophil count in both placebo- and AZD5069-treated subjects. Superoxide anion production in E. coli-stimulated neutrophils and phagocytosis of E. coli were unaffected by AZD5069 (P = 0.375, P = 0.721, respectively vs. baseline, Day 4). AZD5069 was well tolerated.

CONCLUSIONS

CXCR2 antagonism did not appear adversely to affect the mobilization of neutrophils from bone marrow into the peripheral circulation, phagocytosis or the oxidative burst response to bacterial pathogens. This supports the potential of CXCR2 antagonists as a treatment option for diseases in which neutrophils play a pathological role.

Haematological toxicity of clozapine and some other drugs used in psychiatry

OBJECTIVE

To review recent work on the haematological toxicity of clozapine and some other drugs used in psychiatry concerning especially (i) the mechanism of antipsychotic-induced neutropenia/agranulocytosis, (ii) criteria for clozapine prescribing in benign ethnic neutropenia, (iii) options in the event of worrying falls in white cell count (WCC), including measures to boost WCC with or without continued clozapine administration, (iv) criteria for clozapine rechallenge in the event that treatment was suspended because of a fall in WCC and (v) safety concerns regarding clozapine in children/adolescents.

CONCLUSIONS

There remain several difficult areas, including the criteria for clozapine rechallenge. Experience has emphasised (i) the role of appropriate timing of WCC sample collection to ensure that clozapine is not withdrawn unnecessarily and (ii) the success of agents such as filgrastim in promoting rapid production of granulocytes if the situation so demands. On the other hand, the use of lithium to promote a leucocytosis has taken hold without a clear risk: benefit analysis. Be this as it may, should patients decide that they no longer wish to undergo WCC monitoring after 12 months on clozapine, cessation of monitoring is probably preferable to stopping the drug since overall mortality is decreased in patients treated with clozapine.

Leukocyte telomere length in healthy Caucasian and African-American adolescents: relationships with race, sex, adiposity, adipokines, and physical activity

OBJECTIVE

To examine the relationships of race, sex, adiposity, adipokines, and physical activity to telomere length in adolescents.

STUDY DESIGN

Leukocyte telomere length (T/S ratio) was assessed cross-sectionally in 667 adolescents (aged 14-18 years; 48% African-Americans; 51% girls) using a quantitative polymerase chain reaction method. Generalized estimating equations analyses were performed.

RESULTS

Telomere length was greater in the African-American adolescents than in the Caucasian adolescents (age- and sex-adjusted T/S ratio ± SE, 1.32 ± 0.01 vs 1.27 ± 0.01: P = .014) and greater in girls than in boys (age- and race-adjusted T/S ratio ± SE, 1.31 ± 0.01 vs 1.27 ± 0.01; P = .007). None of the adiposity or adipokine measures explained a significant proportion of the variance in telomere length. Vigorous physical activity was positively associated with telomere length (adjusted R(2) = 0.019; P = .009) and accounted for 1.9% of the total variance only in girls.

CONCLUSIONS

This study, conducted in a biracial adolescent cohort, demonstrated that (1) race and sex differences in telomere length have already emerged during adolescence; (2) adiposity and adipokines are not associated with telomere length at this age; and (3) the antiaging effect of vigorous physical activity may begin in youth, especially in girls.

Hematological reference values for healthy adults in togo

The hematological reference values are very important for diagnostic orientation and treatment decision. The aim of this study was to establish hematological reference values for healthy adults in Togo. A total of 2571 voluntary blood donors participated to this study. Only 1349 subjects negative for HIV, HBV, HCV, malaria, and without hemoglobin abnormalities in electrophoresis and hypochromia on blood smear, were definitively retained for the study. Median hemoglobin level was higher in males than females (15.1 g/dL versus 13.0 g/dL, p = 0.000). Median total WBC (4.2×10⁹/L) and absolute neutrophil counts (1.6×10⁹/L) were similar by gender. The median lymphocyte counts in males and females were, respectively, 2.1×10⁹/L and 2.2×10⁹/L (p = 0.11). The median platelet count was lower in males than females (236×10⁹/L versus 247×10⁹/L, p = 0.004). Our median values for RBC parameters differ from those of African countries probably because of our inclusion criteria which eliminate most cases with iron deficiency and/or thalassemia.

The Duffy-null state is associated with a survival advantage in leukopenic HIV-infected persons of African ancestry

Persons of African ancestry, on average, have lower white blood cell (WBC) counts than those of European descent (ethnic leukopenia), but whether this impacts negatively on HIV-1 disease course remains unknown. Here, in a large natural history cohort of HIV-infected subjects, we show that, although leukopenia (< 4000 WBC/mm(3) during infection) was associated with an accelerated HIV disease course, this effect was more prominent in leukopenic subjects of European than African ancestry. The African-specific -46C/C genotype of Duffy Antigen Receptor for Chemokines (DARC) confers the malaria-resisting, Duffy-null phenotype, and we found that the recently described association of this genotype with ethnic leukopenia extends to HIV-infected African Americans (AAs). The association of Duffy-null status with HIV disease course differed according to WBC but not CD4(+) T-cell counts, such that leukopenic but not nonleukopenic HIV(+) AAs with DARC -46C/C had a survival advantage compared with all Duffy-positive subjects. This survival advantage became increasingly pronounced in those with progressively lower WBC counts. These data highlight that the interaction between DARC genotype and the cellular milieu defined by WBC counts may influence HIV disease course, and this may provide a partial explanation of why ethnic leukopenia remains benign in HIV-infected AAs, despite immunodeficiency.

Leukocyte telomere dynamics and human hematopoietic stem cell kinetics during somatic growth

OBJECTIVE

A central question in stem cell research is knowing the frequency of human hematopoietic stem cells (HSC) replication in vivo.

MATERIALS AND METHODS

We have constructed a model that characterizes HSC kinetics and the relative sizes of the hematopoietic progenitor cell (HPC) and HSC pools from birth onward. The model capitalizes on leukocyte telomere length (LTL) data and body weight-gain charts from birth to the age of 20 years. The core premise of the model is that during human growth, LTL dynamics (birth LTL and age-dependent LTL shortening afterward) chronicle the expansions of the HSC and HPC pools.

RESULTS

The model estimates that by the end of the first year of life, HSC have replicated approximately 17 times and they replicate approximately 2.5 times/year between the ages of 3 and 13 years. Subsequently, HSC replication slows considerably. In adults HSC replicate at a rate of approximately 0.6 times/year. In addition, the model predicts that newborns with small birth weight would have shorter LTL as adults and that women would have longer LTL than men.

CONCLUSION

Our findings will be useful in bone marrow transplantations and might explain a body of clinical observations related to LTL distribution in the general population.

[Reference values in the usual laboratory data for sub-Saharan immigrants. Importance in the management of infectious diseases]

BACKGROUND AND AIMS

The progressive increase in the number of immigrants to Spain in recent years has made it necessary for health-care professionals to be aware about the specific characteristics of this population. An attempt is made in this study to define the normal range of common laboratory values in healthy sub-Saharan adults.

SUBJECTS AND METHODS

Common laboratory values were studied (blood cell counts, clotting tests and blood biochemistry values) and were measured in 150 sub-Saharan immigrants previously defined as healthy according to a complete health evaluation that included a clinical history, physical examination, serologic tests and study of stool parasites. These results were compared to those from a control group consisting of 81 age-and-sex matched healthy blood donors taken from the Spanish native population.

RESULTS

Statistically significant differences were obtained in the following values. Mean corpuscular volume (MCV), red cell distribution width (RDW), total leukocytes, and serum levels of creatinine, uric acid, total protein content, creatin-kinase (CK), aspartate aminotransferase (AST), gamma-glutamyl-transpeptidase (GGT), Immunoglobulin G (IgG) and M (IgM). If evaluated according to the normal values in native people, a considerable percentage of healthy sub-Saharan immigrants would present <<abnormal>> values (with potential clinical relevance) in the following parameters. MCV, RDW, total leukocyte counts and serum levels of CK, IgG and IgM.

CONCLUSIONS

A proper interpretation of the common laboratory values in sub-Saharan immigrants, and probably in other foreign collectives, requires a previously-established range of normality in these parameters for those populations in order to avoid diagnostic mistakes and inadequate work-up and management.

Reduced neutrophil count in people of African descent is due to a regulatory variant in the Duffy antigen receptor for chemokines gene

Persistently low white blood cell count (WBC) and neutrophil count is a well-described phenomenon in persons of African ancestry, whose etiology remains unknown. We recently used admixture mapping to identify an approximately 1-megabase region on chromosome 1, where ancestry status (African or European) almost entirely accounted for the difference in WBC between African Americans and European Americans. To identify the specific genetic change responsible for this association, we analyzed genotype and phenotype data from 6,005 African Americans from the Jackson Heart Study (JHS), the Health, Aging and Body Composition (Health ABC) Study, and the Atherosclerosis Risk in Communities (ARIC) Study. We demonstrate that the causal variant must be at least 91% different in frequency between West Africans and European Americans. An excellent candidate is the Duffy Null polymorphism (SNP rs2814778 at chromosome 1q23.2), which is the only polymorphism in the region known to be so differentiated in frequency and is already known to protect against Plasmodium vivax malaria. We confirm that rs2814778 is predictive of WBC and neutrophil count in African Americans above beyond the previously described admixture association (P = 3.8×10⁻⁵), establishing a novel phenotype for this genetic variant.

Many African Americans have white blood cell counts (WBC) that are persistently below the normal range for people of European descent, a condition called “benign ethnic neutropenia.” Because most African Americans have both African and European ancestors, selected genetic variants can be analyzed to assign probable African or European origin to each region of each such person's chromosomes. Previously, we found a region on chromosome 1 where increased local African ancestry completely accounted for differences in WBC between African and European Americans, suggesting the presence of an African-derived variant causing low WBC. Here, we show that low neutrophil count is predominantly responsible for low WBC; that a dominant, European-derived allele contributes to high neutrophil count; and that the frequency of this allele differs in Africans and Europeans by >91%. Across the chromosome 1 locus, only the well-characterized “Duffy” polymorphism was this differentiated. Neutrophil count was more strongly associated to the Duffy variant than to ancestry, suggesting that the variant itself causes benign ethnic neutropenia. The African, or “null,” form of this variant abolishes expression of the “Duffy Antigen Receptor for Chemokines” on red blood cells, perhaps altering the concentrations and distribution of chemokines that regulate neutrophil production or migration.

Duffy (Fy), DARC, and neutropenia among women from the United States, Europe and the Caribbean

Neutropenia associated with race/ethnicity has essentially been unexplained and, although thought to be benign, may affect therapy for cancer or other illnesses. A recent study linked a single nucleotide polymorphism (SNP) (rs2814778) in the Duffy antigen/receptor chemokine gene (DARC) with white blood cell count. We therefore analysed the association of the rs2814778 CC, TC and TT genotypes with absolute neutrophil count (ANC) among asymptomatic women from the Caribbean, Europe and the United States. Among 261 study participants, 33/47 women from Barbados/Trinidad-Tobago, 34/49 from Haiti, 26/37 from Jamaica, and 29/38 US-born black women, but only 4/50 from the Dominican Republic and 0/40 US- or European-born whites (P = 0.0001) had the CC genotype. In a linear regression model that included percentage African ancestry, national origin, cytokines, socio-economic factors and the ELA2 rs57834246 SNP, only the DARC rs2814778 genotype and C-reactive protein were associated with ANC (P < 0.0001). Women with the CC genotype had lower ANC than other women. Further research is needed on the associations of rs2814778 genotype with neutropenia and treatment delay in the setting of cancer. A better understanding of these associations may help to improve cancer outcomes among individuals of African ancestry.

Leukocyte telomeres are longer in African Americans than in whites: the National Heart, Lung, and Blood Institute Family Heart Study and the Bogalusa Heart Study

Leukocyte telomere length (LTL) is ostensibly a bio-indicator of human aging. Here we report that African Americans have longer LTL than whites. We studied cross-sectionally 2453 individuals from the National Heart, Lung, and Blood Institute (NHLBI) Family Heart Study (age = 30-93 years) and the Bogalusa Heart Study (age = 19-37 years), comprising 1742 whites and 711 African Americans. We measured LTL by Southern blots of the terminal restriction fragments length. In 234 participants, telomere repeats were also measured by quantitative polymerase chain reaction (qPCR). Adjusted for age and body mass index (BMI), the respective leukocyte telomere lengths (mean +/- SEM) were considerably longer in African Americans than in whites both in the Family Heart Study (7.004 +/- 0.033 kb vs. 6.735 +/- 0.024 kb, p < 0.0001) and the Bogalusa Heart Study (7.923 +/- 0.063 kb vs. 7.296 +/- 0.039 kb, p < 0.0001). We confirmed the racial effect on LTL by qPCR (3.038 +/- 0.565 T/S units for African Americans vs. 2.714 +/- 0.487 T/S units for whites, p < 0.001). Cross-sectionally, sex- and BMI-adjusted LTL became shorter with age (range 19-93 years) at a steeper slope in African Americans than in whites (0.029 kb year(-1) vs. 0.020 kb year(-1), respectively, p = 0.0001). We suggest that racial difference in LTL arises from a host of interacting biological factors, including replication rates of hematopoietic stem cells.

Duffy antigen modifies the chemokine response in human endotoxemia

OBJECTIVE

The Duffy receptor is a promiscuous receptor for chemokines and selectively binds CXC and CC chemokines with high affinity. Preclinical data show that presence of the Duffy receptor on red blood cells may influence plasma levels of proinflammatory cytokines and chemokines and be protective during inflammation. This trial was designed to investigate the influence of the Duffy antigen on human inflammation in vivo.

DESIGN

Prospective, analyst-blinded clinical trial.

PATIENTS

A total of 32 healthy male volunteers: 16 Duffy-positive white subjects and 16 Duffy-negative subjects of African descent.

MEASUREMENTS AND MAIN RESULTS

All subjects received an intravenous bolus of 2 ng/kg endotoxin (lipopolysaccharide). Cytokines, chemokines, and their receptors were quantified by enzyme immunoassay, reverse transcriptase-polymerase chain reaction, and flow cytometry.

RESULTS

Plasma levels of tumor necrosis factor, interleukin-6, interleukin-10, and whole blood growth-related oncogen-alpha, monocyte chemoattractant protein-1, and interleukin-8 messenger RNA increased similarly in both groups after lipopolysaccharide infusion. Monocyte chemoattractant protein-1 peak plasma levels were roughly two-fold higher in Duffy-positive subjects compared with Duffy-negative subjects (16 ng/mL vs. 7 ng/mL, p < .0001). Similarly, growth-related oncogen-alpha levels were 2.5-fold higher in Duffy-positive subjects 2 hrs after lipopolysaccharide infusion (210 pg/mL vs. 85 pg/mL; p < .001). Erythrocyte-bound monocyte chemoattractant protein-1, growth-related oncogen-alpha, and interleukin-8 increased 20- to 50-fold in Duffy-positive subjects (p < .00001 vs. baseline).

CONCLUSION

The Duffy antigen substantially alters chemokine concentrations in blood, but it does not have a protective effect during human endotoxemia.

Lymphocyte subsets in healthy adult Kuwaiti Arabs with relative benign ethnic neutropenia

Relative and absolute neutropenia is frequently seen in the healthy adult Kuwaiti Arab population. Fluorescent monoclonal antibody labelling followed by flow cytometry was used to determine the lymphocyte subsets in 48 normal healthy individuals in the Kuwaiti adult population (24 males and 24 females, age 17-59 years) with relative or absolute neutropenia, and this was compared to age-matched controls (64 males and 63 females). The mean haemoglobin levels were 13.6+/-1.5 and 13.7+/-1.5 g/dl in the neutropenic and control groups, respectively. White blood cell counts, absolute neutrophil and lymphocyte counts in neutropenic individuals with the corresponding reference range, taken from the control subjects (in parenthesis) were: WBC, 6.7+/-1.6 x 10(9)/l (4-10.4 x 10(9)/l), neutrophils, 2.7+/-0.8 x 10(9)/l (1.87-6.63 x 10(9)/l), lymphocytes, 3.3+/-0.9 x 10(9)/l (1.4-3.62 x 10(9)/l). Absolute values of lymphocytes, CD2+, CD3+, CD19+, CD4+, CD8+, HLADR+ and CD45RA+ cells were significantly higher in the neutropenic group. The range of values with the corresponding reference ranges, in parenthesis, were: CD2+, 1.61-4.30 x 10(9)/l (0.95-2.99 x 10(9)/l), CD3+, 1.37-4.16 x 10(9)/l (0.83-2.71 x 10(9)/l), CD19+, 0.16-1.09 x 10(9)/l (0.05-0.61 x 10(9)/l), CD4+, 0.70-2.89 x 10(9)/l (0.45-1.65 x 10(9)/l), CD8+, 0.57-1.80 x 10(9)/l (0.29-1.17 x 10(9)/l), HLADR+ 0.27-1.74 x 10(9)/l (0.02-0.62 x 10(9)/l), CD45RA, 0.90-4.63 x 10(9)/l (0.34-2.05 x 10(9)/l), respectively. The levels of natural killer cells, CD56+ cells were significantly lower compared to controls while the values of memory T lymphocytes, CD45RO+ were comparable to controls. These results indicate that difference in the leukocyte subpopulations may also be indicative of differences in the lymphocyte subpopulations and that reference ranges for these cell types in healthy neutropenic and non-neutropenic individuals should be established.

Ethnic Neutropenia and Treatment Delay in African American Women Undergoing Chemotherapy for Early-Stage Breast Cancer

Disparities in breast cancer survival have been observed between African American and white women. There are also known differences in mean baseline white blood cell (WBC) count among racial and ethnic groups. If the WBC count falls below conventionally defined treatment thresholds for patients undergoing adjuvant chemotherapy, reduced doses or treatment delays may occur, which could lead to race-based differences in treatment duration. We used the tumor registry at Columbia-Presbyterian Medical Center to identify 1178 women with newly diagnosed stage I and II breast cancer from whom we collected base-line information for 73 African American women and 126 age- and tumor stage-matched white women. Of these women, 43 African American and 93 white women underwent adjuvant chemotherapy. African American women had statistically significantly lower WBC counts than white women at diagnosis (6.2 x 10(9)/L for African American women versus 7.4 x 10(9)/L for white women, difference = 1.2, 95% confidence interval [CI] = 0.2 to 1.2; P =.02) and after treatment (5.3 x 10(9)/L for African American women versus 6.4 x 10(9)/L for white women, difference = 1.1, 95% CI = 0.2 to 2.5; P =.03). Overall, African American women required a statistically significantly longer duration of treatment than white women (19 weeks versus 15 weeks, respectively, difference = 4 weeks, 95% CI = 0.5 to 7.2 weeks; P =.03). The lower baseline WBC counts and longer duration of treatment for early-stage breast cancer in African American women compared with those in white women result in lower dose intensity of treatment for African American women, possibly contributing to observed racial differences in breast cancer survival.

Adhesion molecules, catecholamines and leucocyte redistribution during and following exercise

The circulating blood normally contains no more than 1-2% of the body's population of leucocytes. The numbers and phenotypes of circulating leucocyte subsets can change dramatically during and immediately following exercise. The surface expression of adhesion molecules makes an important contribution to such responses by changing patterns of cell trafficking. Alterations in the surface expression of adhesion molecules could reflect a shedding of molecules, selective apoptosis or differential trafficking of cells with a particular phenotype, effects from mechanical deformation of the cytoplasm, active biochemical processes involving cytokines, catecholamines, glucocorticoids or other hormones, or changes in the induction of adhesion molecules. The expression of adhesion molecules changes with maturation and activation of leucocytes. Typically, mature cells express lower densities of L-selectin (CD62L), the homing receptor for secondary lymphoid organs, and higher densities of LFA-1 (CD11a), the molecule associated with trafficking to non-lymphoid reservoir sites. The neutrophils and natural killer cells that are mobilised during exercise also express high levels of Mac-1 (CD11b), a marker associated with cellular activation. Possibly, exercise demarginates older cells that are awaiting destruction in the spleen. Plasma concentrations of catecholamines rise dramatically with exercise, and there is growing evidence that catecholamines, acting through a cyclic adenosine monophosphate second messenger system, play an important role in modifying the surface expression of adhesion molecules. Analogous changes can be induced by other forms of stress that release catecholamines or by catecholamine infusion, and responses are blocked by beta(2)-blocking agents. Catecholamines also modify adherence and expression of adhesion molecules in vitro. Cell trafficking is modified by genetic deficiencies in the expression of adhesion molecules, but leucocyte responses to exercise and catecholamines are generally unaffected by splenectomy. A number of clinical conditions including atherogenesis and metaplasia are marked by an altered expression of adhesion molecules. The effects of exercise on these molecules could thus have important health implications.

Investigation of the effect of marathon running on leucocyte counts of subjects of different ethnic origins: relevance to the aetiology of ethnic neutropenia

Healthy subjects of African ancestry, including Afro-Caribbeans, have been observed to have lower total white cell counts and neutrophil counts than healthy Caucasian subjects. The cause of this ethnic neutropenia is unclear. We have previously found no evidence that increased margination of neutrophils is responsible. In this study, we have investigated mobilization of neutrophils from the bone marrow granulocyte reserve by endurance exercise. We investigated subjects of different ethnic origins before and after they had competed in a marathon race. Before the race, the neutrophil counts of Africans/Afro-Caribbeans were significantly lower than those of Caucasians (means 2.49 and 3.21 x 109/l respectively; P = 0.043). After the race, the difference was greater, as was the degree of significance (means 10.21 and 12.33 respectively; P = 0.017). The percentage increment was almost identical whereas the absolute increment was considerably less, although of marginal statistical significance (increment 7.72 and 9. 12 x 109/l respectively; P = 0.10). Similar changes were observed in the monocyte count. Before the race, the difference in the means was of marginal statistical significance (0.35 and 0.41 x 109/l respectively; P = 0.105), whereas after the race the difference was greater and was highly significant (means 0.75 and 1.05 x 109/l respectively; P = 0.001). These observations support the results of our earlier study, both of which suggested that ethnic neutropenia is likely to result from a diminished bone marrow reserve rather than being consequent on altered distribution of neutrophils within the blood stream.