Prolonged neutropenia due to antihuman neutrophil antigen 2 (CD177) antibody after bone marrow transplantation

Dual role of CD177 + neutrophils in inflammatory bowel disease: a review

Inflammatory bowel disease (IBD) represents a group of recurrent chronic inflammatory disorders associated with autoimmune dysregulation, typically characterized by neutrophil infiltration and mucosal inflammatory lesions. Neutrophils, as the earliest immune cells to arrive at inflamed tissues, play a dual role in the onset and progression of mucosal inflammation in IBD. Most of these cells specifically express CD177, a molecule increasingly recognized for its critical role in the pathogenesis of IBD. Under IBD-related inflammatory stimuli, CD177 is highly expressed on neutrophils and promotes their migration. CD177 + neutrophils activate bactericidal and barrier-protective functions at IBD mucosal inflammation sites and regulate the release of inflammatory mediators highly correlated with the severity of inflammation in IBD patients, thus playing a dual role. However, mitigating the detrimental effects of neutrophils in inflammatory bowel disease remains a challenge. Based on these data, we have summarized recent articles on the role of neutrophils in intestinal inflammation, with a particular emphasis on CD177, which mediates the recruitment, transepithelial migration, and activation of neutrophils, as well as their functional consequences. A better understanding of CD177 + neutrophils may contribute to the development of novel therapeutic targets to selectively modulate the protective role of this class of cells in IBD.

Neutrophil antigen antibodies affect engraftment and secondary graft failure in hematopoietic progenitor cell transplantation

BACKGROUND

Research is limited on the role of antibodies against human neutrophil antigen (HNA) in hematopoietic progenitor cell (HPC) transplantation outcomes.

STUDY DESIGN AND METHODS

A retrospective review was conducted on medical records of patients at the NIH Clinical Center enrolled in six research protocols. This case-control study included 21 patients tested for HNA antibodies from January 2010 to March 2022 who underwent HPC transplantation. In addition, 42 patients following the same research protocols were randomly selected as a control group.

RESULTS

The cumulative incidence of time to neutrophil engraftment was significantly impacted by the patients' anti-HNA status (p = .042), with the patients with anti-HNA experiencing delayed engraftment. Secondary graft failure occurred in 4 out of 42 patients (9.52%; 95% confidence interval [CI]: 3.7-22.1) of the control group, while 5 out of 9 patients (55.5%; 95% CI: 26.7-81.1) with anti-HNA experienced secondary graft failure (p = .005). Furthermore, patients with anti-HNA had a lower proportion (p = .008 for full and p = .002 for partial chimerism) and cumulative incidence (p = .016 for full and p = .010 for partial chimerism) of achieving donor chimerism compared to the control group.

DISCUSSION

The study reveals a potential link between anti-HNA and HPC transplantation outcomes not previously reported. Patients with anti-HNA had a lower proportion and cumulative incidence of achieving donor chimerism. Additionally, anti-HNA status affected the time for neutrophil engraftment, with a slower rate of neutrophil engraftment and increased risk of secondary failure in patients with anti-HNA.

Comparison of real-time quantitative PCR and two digital PCR platforms to detect copy number variation in FCGR3B

The importance of structural genetic variants, such as copy number variations (CNVs), in modulating human disease is being increasingly recognized. Several clinical conditions require investigation of human neutrophil antigen (HNA-1), which is encoded by the Fc gamma receptor IIIb gene (FCGR3B), including suspicion of neutropenia, infections, and proactive testing of blood component donors to reduce the potential risk in transfusion. In this study, we compared real-time quantitative polymerase chain reaction (qPCR) with two digital PCR (dPCR) platforms, namely droplet digital PCR and an array-based platform, to determine copy numbers (CNs) in FCGR3B. We initially tested 400 anonymous blood donors with qPCR using a commercially available TaqMan probe assay (Applied Biosystems) on a Quant Studio 12 Flex. CNs was determined for all 400 tested individuals with CNs ranging from zero to four. Zero copies were detected in 0.2% (1/400), one copy was detected in 3.8% (15/400), two copies were detected in 87.8% (351/400), three copies were detected in 8.0% (32/400), and four copies were detected in 0.2% (1/400) of tested individuals. From this cohort, we selected 32 donors with CNs from zero to four for analyses with Digital Real-Time PCR (dPCR) using Lab on an array (LOAA) on an On-Point analyzer from Optolane Technologies Inc. and the Droplet Digital PCR (ddPCR) platform from Bio-Rad Laboratories. We compared the obtained CNs of FCGR3B on the three platforms and found full concordance between the CNs obtained. We therefore conclude that all three platforms can be used for quantification of CNs for FCGR3B, and although dPCR has some advantages over qPCR, it was not necessary for reliably estimating CNs of the FCGR3B gene.

Autoimmune diseases after allogeneic stem cell transplantation: a clinician's guide and future outlook

INTRODUCTION

Autoimmune disease (AD) may occur after allogeneic hematopoietic stem cell transplantation (HSCT). The autoimmune mechanism seems to be related to an imbalance of the immune regulation effect of T-regulatory lymphocytes on autoreactive T-lymphocytes.

AREAS COVERED

ADs include hematological ADs (HADs) and nonhematologic ADs (NHADs) involving organs such as thyroid, peripheral and central nervous system, skin, liver, connective tissue, gastrointestinal tract, and kidney. To identify the risk factors for ADs, to report their clinical characteristics, and to discuss new approaches represent the areas covered in this review.

EXPERT OPINION

Some risk factors for HAD and NHAD are common and include nonmalignant diseases, young age, cord blood as a stem cell source, conditioning regimens without total body irradiation, alemtuzumab, antithymocyte globulin, T-cell-depleted transplant, some viral infection, mixed chimerism, and chronic Graft versus Host Disease. In NHADs, the detection of autoantibodies is more frequent and the transfer of autoimmunity from the donor to the recipient represents the pathogenetic mechanism responsible for these complications. New therapeutic approaches such as bortezomib, daratumumab, sirolimus, eculizumab, and eltrombopag appear to be promising in terms of better efficacy and reduced toxicity compared to traditional therapies. New horizons based on personalized therapies will allow us to improve the prognosis of AD.

Human neutrophil antigen 2 sequence-based typing: Joining the hunt for the CD177 answer

BACKGROUND AND OBJECTIVES

Isoantibodies to human neutrophil antigen 2 (CD177) have been associated with several clinical conditions but to date the molecular basis for altered or non-expression has not been determined. Reliance on phenotyping and crossmatch to investigate these neutropenic clinical cases are inconvenient for the patients and demanding of resources within the laboratory. Therefore, a molecular approach has been introduced to address both issues.

MATERIALS AND METHODS

A DNA panel of 100 randomly selected blood donors were collected and supplemented with 18 DNA samples from blood donors previously shown to be CD177 null. All DNA samples were sequence-based typed for all exons and observed polymorphisms recorded. The DNA from two families previously investigated for neonatal alloimmune neutropenia due to CD177 isoantibodies were also analysed.

RESULTS

The incidence of CD177 null could be associated with a known exon 7 single-nucleotide polymorphism in 16/21 known CD177 null samples, which is consistent with previously published findings. Two additional mutations that may lead to null expression were also identified, of which one may be novel. In both family investigations, this same mutation could also be observed in the maternal DNA sample.

CONCLUSION

Based on these observations, introduction of CD177 genotyping into routine use would identify null expression in over 75% (16/21) of associated cases. In turn, this could significantly reduce the need for supplementary testing and associated inconvenience to patients while permitting increased efficiency of laboratory testing. An added benefit would potentially elucidate other clinically relevant mutations and associated antigenic targets.

Human neutrophil antigens: Nature, clinical significance and detection

Granulocytes are an essential part of both the innate and adaptive immune systems. Human neutrophil antigens (HNAs) are a family of epitopes that are located on glycoproteins that are mostly expressed on human granulocytes. Antibodies that recognize these epitopes have been associated with neutropenia, transfusion complications, haematopoietic stem cell transplant nonengraftment and renal transplant rejection. Currently, there are fourteen recognized HNA alleles across five antigen systems (HNA-1 through HNA-5), the molecular basis of which are located on the genes FCGR3B, CD177, SLC44A2, ITGAM and ITGAL, respectively. Elucidation of the associated genes has permitted the development of testing strategies for HNA typing and aided understanding of the associated epitopes. This review will outline the associated clinical conditions that require HNA investigation and how these are performed in specialized laboratories. Investigations provided are both reactive for patients with a variety of existing or suspected neutropenias and proactive in the testing of blood component donors in order to reduce the potential risk to patients who require transfusion.

[Relevance of antibodies in hematopoietic stem cell transplantation: Antibodies anti-HLA, anti-platelets, anti-granulocytes, anti-erythrocytes and anti-MICA. Guidelines from the Francophone Society of Bone Marrow Transplantation and Cellular Therapy (SFGM-TC)]

The presence of allo-antibodies in the serum of a recipient awaiting hematopoietic stem cell transplantation (HSCT) may have an impact on transfusion efficiency and/or donor choice, especially in the absence of an identical sibling donor. Prior to transplantation, donor specific anti-HLA (Human Leukocyte Antigen) antibodies (DSA) have a recognized effect on transplant outcome, correlated with the increasing MFI value and with the ability of such antibody to fix the complement fraction. Anti-platelet antibodies (anti-HLA class I and anti-HPA [Human Platelet Antigen]) are better involved in transfusion inefficiency and can be responsible for refractory status. ABO incompatibilities require a specific treatment of the graft in presence of high titer to avoid hemolytic adverse effects. Investigations of these antibodies should be carried out on a regular basis in order to establish appropriate transfusion recommendation, select an alternative donor when possible or adapt the source of cells. After transplantation, in case of delayed recovery or graft rejection, long term aplasia, persistent mixed chimerism or late release, and after elimination of the main clinical causes, a biological assessment targeted on the different type of antibodies will have to be performed in order to orient towards the cause or the appropriate therapy. Further studies should be carried out to determine the impact of anti-MICA antibodies and recipient specific anti-HLA antibodies, on the outcome of the transplantation.