Neutrophil Effector Functions Are Not Impaired in Duffy Antigen Receptor for Chemokines (DARC)-Null Black South Africans

Novel neutrophil biology insights underlying atypical chemokine receptor-1/Duffy antigen receptor of chemokines-associated neutropenia

PURPOSE OF REVIEW

Atypical chemokine receptor-1 (ACKR1)/Duffy antigen receptor of chemokines (DARC)-associated neutropenia (ADAN; OMIM 611862), previously named benign ethnic neutropenia, and present in two-thirds of individuals identifying as Black in the USA, is associated with mild to moderate decreases in peripheral neutrophil counts that nevertheless do not lead to increased infections. Consequently, recent initiatives have sought to establish normal neutrophil count reference ranges for ADAN, considering it a normal variant rather than a clinical disorder requiring medical intervention.

RECENT FINDINGS

A limited number of studies elucidating the mechanism of neutropenia in ADAN has suggested that neutrophils may redistribute from peripheral blood to the tissues including the spleen: this might explain why ADAN is not associated with increased risks of infection since the total number of neutrophils in the body remains normal. In this review, we critically examine the research underlying the molecular basis of ADAN.

SUMMARY

Insights into the biology of neutrophils and their trafficking may inform the clinical interpretation of neutropenia in ADAN. The bulk of research suggests that ADAN does not lead to a diminished host defense as do other forms of neutropenia. However, ADAN may lead to increased proinflammatory signaling, with possible implications for senescence of the immune system and predisposition to autoimmunity and cancer.

Disparities in relapsed or refractory multiple myeloma: recommendations from an interprofessional consensus panel

Many studies have documented racial, socioeconomic, geographic, and other disparities for United States (US) patients with multiple myeloma pertaining to diagnosis and frontline management. In contrast, very little is known about disparities in the management of relapsed/refractory multiple myeloma (RRMM) despite a plethora of novel treatment options. In this review, we discuss the manifestations of disparities in RRMM and strategies to mitigate their impact. Immunomodulatory drugs can create disparities on many axes, for example inappropriately low dosing due to Duffy-null status as well as time toxicity and financial toxicity from logistical hurdles for socioeconomically vulnerable patients. Access to myeloma expertise at high-volume centers is a critical consideration given the disconnect between how drugs like carfilzomib and dexamethasone are prescribed in trials versus optimized in real-world practice to lower toxicities. Disparities in chimeric antigen receptor T-cell therapy and bispecific antibody therapy span across racial, ethnic, and socioeconomic lines in large part due to their limited availability outside of high-volume centers. Another insidious source of disparities is supportive care in RRMM, ranging from inadequate pain control in Black patients to limited primary care provider access in rural settings. We discuss the rationales and evidence base for several solutions aimed at mitigating these disparities: for example, (1) bidirectional co-management with community-based oncologists, (2) screening for risk factors based on social determinants of health, (3) strategies to build patient trust with regard to clinical trials, and (4) longitudinal access to a primary care provider. As the treatment landscape for RRMM continues to expand, these types of efforts by the field will help ensure that this landscape is equally accessible and traversable for all US patients.

Duffy-Null Phenotype-Associated Neutropenia is the Most Common Etiology for Leukopenia/Neutropenia Referrals to a Tertiary Children's Hospital

Duffy-null phenotype-associated neutropenia was present in 77.7% of leukopenia/neutropenia referrals to our center in Detroit with a high prevalence in Yemeni (96.6%), African American (91%), and non-Yemeni Middle Eastern (52.9%) patients. Greater availability of Duffy typing in patients with neutropenia but without recurrent/frequent/serious infections may lessen the need for additional consultations and investigations.

Disparities in Breast Cancer Associated With African American Identity

Persistent disparities in the burden of breast cancer between African Americans and White Americans have been documented over many decades. Features characterizing breast cancer in the African American community include a 40% higher mortality rate, younger age distribution, greater advanced-stage distribution, increased risk of biologically aggressive disease such as the triple-negative phenotype, and increased incidence of male breast cancer. Public health experts, genetics researchers, clinical trialists, multidisciplinary oncology teams, and advocates must collaborate to comprehensively address the multifactorial etiology of and remedies for breast cancer disparities. Efforts to achieve breast health equity through improved access to affordable, high-quality care are especially imperative in the context of the COVID-19 pandemic and its disproportionately high economic toll on African Americans.

The DARC-null trait is associated with moderate modulation of NK cell profiles and unaltered cytolytic T cell profiles in black South Africans

The Duffy Antigen Receptor for Chemokines (DARC)-null trait, common among persons of African descent and associated with lower absolute neutrophil counts (ANCs), may be linked to increased risk to certain infections including HIV-1 but the underlying causes are poorly understood. We hypothesized that DARC-null-linked neutropenia may negatively impact neutrophil immunoregulatory modulation of other immune cells such as natural killer (NK) and CD8+ T cells leading to altered phenotype, functionality and homeostatic activity of these immune cells. HIV-1 uninfected (n = 20) and HIV-1 chronically infected (n = 19) participants were assessed using multi-parametric flow cytometry to determine NK and CD8+ T cell counts, phenotypic profiles, and cytokine production and degranulation. Annexin V and carboxyfluorescein succinimidyl ester (CFSE) staining were used to examine NK cell survival and NK cell and CD8+ T cell proliferation respectively. Participants were genotyped for the DARC-null polymorphism using allelic discrimination assays and ANCs were measured by full blood count. In HIV uninfected individuals, a reduction of total NK cell counts was noted in the absence of DARC and this correlated with lower ANCs. HIV uninfected DARC-null subjects displayed a less mature NK cell phenotype. However, this did not translate to differences in NK cell activation or effector functionality by DARC state. Whilst HIV-1 infected subjects displayed NK cell profiling that is typical of HIV infection, no differences were noted upon DARC stratification. Similarly, CD8+ T cells from HIV infected individuals displayed phenotypic and functional modulation that is characteristic of HIV infection, but profiling was unaffected by the DARC-null variant irrespective of HIV status. Overall, the data suggests that the DARC-null polymorphism and lower ANCs does not impede downstream cytolytic cell priming and functionality.

Duffy phenotyping and FY*B-67T/C genotyping as screening test for benign constitutional neutropenia

OBJECTIVE

Low levels of neutrophils can be an intrinsic condition, with no clinical consequences or immunity impairment. This condition is the benign constitutional neutropenia (BCN), defined as an absolute neutrophils count (ANC) ≤2000 cells/mm. Diagnosis of BCN is of exclusion where patients are submitted to blood tests and possibly to invasive diagnostic search until secondary causes of neutropenia are ruled out. The natural history of the disease suggests benign evolution and Brazilian study showed an overall frequency of 2.59%. The main mechanisms include reduced neutrophil production, increased marginalization, extravasation to the tissues and immune destruction. Genetic studies showed strong association between the single nucleotide variant rs2814778 located on chromosome 1q23.2 in the promoter region of the atypical chemokine receptor 1 (Duffy blood group system) gene (ACKR1, also termed DARC) and BCN. The aim of this study is to evaluate FY phenotypes and genotypes including the analysis of the rs2814778 SNP in Brazilian patients with BCN in order to determine an effective diagnostic tool, allowing reassurance of the patient and cost reduction in their care.

METHODS

Case control study, with 94 individuals (18 patients and 76 controls). Phenotyping was performed by gel test and genotyping was performed by PCR-RFLP.

RESULTS

White blood cell (WBC) and absolute neutrophils (AN) counts showed lower levels in patients compared to controls. In the patient group 83.3% were genotyped as FY*B/FY*B. The SNP rs2814778 (-67T > C) was identified in 77.8% of the patients genotyped as FY*B-67C/FY*B-67C. In the control group, 72.7% were homozygous for the wild type and 23.3% were heterozygous.

CONCLUSION

This study reinforces that FY phenotyping and genotyping can be used to detect most people with BCN, avoiding excessive diagnostic investigation. Besides, this procedure may reduce health costs and be reproductible in clinical practice.