Neonatal alloimmune thrombocytopenia caused by anti‐HLA‐A24 alloantibodies

Neonatal alloimmune thrombocytopenia (NAIT) occurs as a result of maternal alloimmunization against paternally inherited antigens on foetal platelets. Platelets express platelet specific antigens (HPA) along with human leucocyte antigens (HLA) class I. Although anti‐HLA class I antibodies are often detectable in pregnant women, their role in NAIT is considered controversial. We report a case of NAIT where the most sensitive serological analysis and molecular methods could not detect platelet specific antibodies. Only HLA incompatibility and presence of anti‐HLA‐A24 antibodies in both the mother’s and the newborn’s serum were proven. Conclusion: This case supports the idea that some anti‐HLA class I antibodies could cause NAIT.     

A man‐made disease: Fetal neonatal alloimmune thrombocytopenia due to incompatibility between oocyte donor and gestational mother

The incompatibility causing fetal and neonatal alloimmune thrombocytopenia (FNAIT) results from a fetus inheriting a paternal human platelet antigen (HPA), which is different from the maternal HPA. We present a unique case of FNAIT in a pregnancy involving an oocyte recipient mother with Turner syndrome. This is the first report of FNAIT in which the suggested mechanism involves antibodies produced by a gestational mother against the incompatible HPA of the oocyte donor.     

Alloimmune neonatal neutropenia and thrombocytopenia associated with maternal anti HNA-1a, HPA-3b and HLA antibodies.

The incidence of alloimmune neonatal neutropenia combined with neonatal alloimmune thrombocytopenia is very low. We report a case of a neonate who suffered severe neutropenia and thombocytopenia with widespread petechial spots. The presence of alloantibodies in mother's and patient's sera was analyzed by lymphocytotoxicity test, agglutination test, granulocyte indirect immunofluorescence test, platelet immunofluorescence test (PIFT) and solid phase enzyme-linked immunosorbent assay. Human neutrophil antigens (HNA) and human platelet antigen (HPA) genotypes were tested by polymerase chain reaction analyses. The mother's and patient's sera reacted with neutrophils and lymphocytes of the father. PIFT revealed the presence of IgG anti-platelet antibodies in the patient's serum but the test was negative in the maternal serum. Analyses of HNA-1 and HPA genotypes of the family revealed maternal-neonatal HNA-1a and HPA-3b mismatch. The study of the mother's and patient's sera showed the presence of anti HNA1a, HPA-3b and HLA antibodies specific for HLA-A3 and HLA-B38 antigens. These results suggest that the transplacental passage of maternal HNA-1a, HPA-3b and HLA alloantibodies caused neutropenia and thrombocytopenia in this patient.     

Neonatal alloimmune thrombocytopenia due to HPA‐9b incompatibility

Neonatal alloimmune thrombocytopenia (NAIT) is one of the most frequent causes of both severe thrombocytopenia and intracranial hemorrhage (ICH) in fetuses and term neonates. The diagnosis is established by demonstrating antibodies against human platelet antigens (HPA) and discordance in platelet antigen typing between parents or between the mother and neonate. We report a case of NAIT that was likely due to maternal sensitization to HPA‐9b (Max^a), a recently recognized, rare platelet‐specific antigen. Pediatr Blood Cancer 2009;53:459–461. © 2009 Wiley‐Liss, Inc.     

Comparison of FDG-PET scans to conventional radiography and bone scans in management of Langerhans cell histiocytosis

Neonatal thrombocytopenia or neutropenia may result from passive transfusion of maternally derived antibodies. Antibodies against platelet antigens are commonly associated with neonatal alloimmune thrombocytopenia (NAIT), and anti‐neutrophil antibodies are frequently identified in alloimmune neonatal neutropenia (ANN). Combined alloimmune cytopenias in the newborn are rarely reported; even fewer reports document human leukocyte antigen (HLA) antibodies as a potential cause of neonatal thrombocytopenia or neutropenia. We describe neutropenia and thrombocytopenia in a newborn associated with markedly elevated maternal HLA antibodies in the absence of anti‐neutrophil or anti‐platelet antibodies to highlight consideration of HLA antibodies in the pathogenesis of ANN and NAIT. Pediatr Blood Cancer 2009;53:97–99. © 2009 Wiley‐Liss, Inc.     

Intramuscular anti‐D in chronic immune thrombocytopenia children with severe thrombocytopenia

Nine patients with chronic immune thrombocytopenia and platelet counts <20 × 10⁹/L, with a median age of 7.8 (3.8–15.5) years, received three phases of 10 mcg/kg/dose of intramuscular anti‐D. Phase 1 was anti‐D daily for 5 days, followed by phase 2, anti‐D weekly for 12 weeks and withheld when platelet counts ≥20 × 10⁹/L, and then phase 3 was anti‐D once every 2 weeks for 24 weeks. According to the International Working Group criteria, in phase 1, 66.7% of patients responded to the treatment. In phases 2 and 3, 11.1% (0–41.7%) and 7.7% (0–33.3%) of total episodes of follow up, respectively, responded to the treatment. Therefore, intramuscular anti‐D given at a dose of 10 mcg/kg for 5 days is an alternative method to raise platelet counts in chronic immune thrombocytopenia children with severe thrombocytopenia where the intravenous form of anti‐D is not available.     

Clinical significance of anti‐HLA antibodies associated with ventricular assist device use in pediatric patients: A United Network for Organ Sharing database analysis

While VAD use in pediatric patients has previously been associated with anti‐HLA antibody production, the clinical significance of these antibodies is unclear. We investigated the clinical impact of anti‐HLA antibodies associated with VAD use in a large cohort of pediatric HTx recipients. From 2004 to 2011, pediatric cardiomyopathy patients post‐HTx (N=1288) with pre‐HTx PRA levels were identified from the United Network for Organ Sharing database. PRA levels were compared between VAD patients and those with no history of MCS. Incidence of rejection and overall survival were compared between VAD and non‐MCS groups after stratification by PRA and age. VAD recipients were more likely to produce anti‐HLA antibodies than non‐MCS patients (25.5% vs 10.5% had PRA>10%, P<.0001). Sensitized VAD patients (PRA>10%) had a higher incidence of rejection within 15 months of HTx compared to sensitized non‐MCS patients (57.1% vs 35.9%, P=.02). There was no intergroup difference in 15‐month mortality. Among pediatric cardiomyopathy patients supported with a VAD, the presence of anti‐HLA antibodies prior to HTx is associated with an increased risk of rejection. The mechanism of the association between VAD‐associated antibodies and early rejection is unclear and warrants further investigation.     

Platelet transfusion refractoriness in highly immunized beta thalassemia children undergoing stem cell transplantation

Marktel S, Napolitano S, Zino E, Cappelli B, Chiesa R, Poli F, Crocchiolo R, Ronchi P, Rossini S, Ciceri F, Roncarolo MG, Fleischhauer K. Platelet transfusion refractoriness in highly immunized beta thalassemia children undergoing stem cell transplantation.
Pediatr Transplantation 2010: 14:393–401. © 2010 John Wiley & Sons A/S. Abstract: Immune‐mediated refractoriness to platelet transfusion is a major problem in patients undergoing HSCT. In a cohort of 50 pediatric patients affected by beta thalassemia coming from Middle East countries, we experienced a high incidence of refractoriness because of anti‐HLA antibodies during post‐HSCT aplasia. In a risk factors analysis, factors predicting a negative transfusion outcome were presence of spleen and the number of anti‐HLA antibodies. We adopted a policy to select platelet donors by avoiding HLA antigens against which the patient had specific antibodies. Transfusion of dedicated units resulted in 26% refractoriness compared to 74% to random units (p < 0.0001). When dedicated transfusions were used, the presence of spleen did not influence transfusion outcome. Analyzing transfusion outcome depending on the degree of HLA match and ABO compatibility, 76% successful transfusions were obtained with HLA‐matched‐ ABO compatible followed by 67% in HLA‐1mismatch‐ ABO compatible or HLA‐matched‐ ABO incompatible and by 46% in HLA‐1mismatch‐ ABO incompatible. In conclusion, we provide evidence that the selection of platelet donors according to patient characteristics, anti‐HLA antibodies and ABO matching, is successful in reducing platelet refractoriness in heavily alloimmunized thalassemia patients undergoing transplantation.     

Neonatal alloimmune thrombocytopenia with significant HLA antibodies

A case of neonatal alloimmune thrombocytopenia (NAIT) secondary to human platelet antigen (HPA)-1a antibodies is reported. Additional multispecific HLA antibodies rendered volunteer donor platelet transfusions ineffective. Despite a high incidence of maternal HLA antibodies in the pregnant population, there is only one previous report of clinically significant HLA antibodies.     

High affinity anti‐BSEP antibodies after liver transplantation for PFIC‐2 – Successful treatment with immunoadsorption and B‐cell depletion

PFIC due to BSEP mutations (PFIC type 2) often necessitates OLT. It has recently been recognized that some PFIC‐2 patients develop phenotypic disease recurrence post‐OLT due to the appearance of anti‐BSEP antibodies. Here, we describe a boy who became cholestatic four yr after OLT during modification of immunosuppression. Canalicular antibody deposits were detected in biopsies of the transplant and antibodies specifically reacting with BSEP were identified at high titers in his serum. These antibodies bound extracellular epitopes of BSEP and inhibited BS transport and were assumed to cause disease recurrence. Consequently, anti‐BSEP antibody depletion was pursued by IA and B‐cell depletion by anti‐CD20 antibodies (rituximab) along with a switch of immunosuppression. This treatment resulted in prolonged relief of symptoms. Depletion of pathogenic anti‐BSEP antibodies causing AIBD after OLT in PFIC‐2 patients should be considered as a central therapeutic goal.     

Fatal graft‐versus‐host disease after living‐donor liver transplantation from an HLA‐DR‐mismatched donor

Acute GVHD is a rare complication after liver transplantation that has a high mortality rate. We experienced an infant case complicated with acute GVHD. An 8‐month‐old infant with biliary atresia underwent LDLT with a graft obtained from his mother. Their HLAs showed a donor‐dominant one‐way match, not at HLA‐DR but at HLA‐A, HLA‐B, and HLA‐C (recipient; A 31/33, B 51/54, C 1/14, DR 9/11, donor; A 31/‐, B 51/‐, C 14/‐, DR 8/11). The patient exhibited a high fever, skin rash, and diarrhea, and was diagnosed with acute GVHD based on the blood chimerism test. Despite immunosuppression treatment with prednisolone and tacrolimus, plasma exchange, blood transfusion including cord blood transplantation, and antibiotics, the child died on postoperative day 126. Donor‐dominant one‐way matching at HLA class 1 can be a high‐risk factor for acute GVHD despite HLA class 2 mismatching.     

Association of Neonatal Thrombocytopenia and Maternal Anti-HLA Antibodies

In order to evaluate the influence of maternal anti-HLA antibody on neonatal thrombocytopenia, clinical features and maternal anti-HLA antibody of three groups of infants (19 thrombocytopenic and low birth weight, 27 nonthrombocytopenic and low birth weight, and 80 healthy full-term) were investigated. The incidence of positive maternal anti-HLA antibodies in the three groups was 73.7%, 29.6% and 27.5%, respectively. Thrombocytopenia in small-for-gestational-age (SGA) infants was closely related to the presence of maternal anti-HLA antibodies. Among 20 SGA infants (11 thrombocytopenic, 9 non-thrombocytopenic), anti-HLA antibody was detected in 10 mothers (90.9%) of thrombocytopenic SGA infants, while it was positive in only one mother (11.1%) of nonthrombocytopenic SGA infants. Investigation of the SGA infants revealed that in those whose mothers were sensitized to HLA antigen, not only the platelet count but also the leukocyte and lymphocyte counts in the first week of life were significantly lower than in infants whose mothers were not sensitized. The results suggest that the presence of maternal anti-HLA antibody is a cause of neonatal thrombocytopenia especially in SGA infants.     

Subcutaneous anti‐D treatment of idiopathic thrombocytopenic purpura in children

We investigated the effect of subcutaneous anti‐D IgG as platelet enhancing therapy in children with idiopathic thrombocytopenic purpura (ITP). Twenty‐three children were treated with subcutaneous anti‐D 50 µg/kg. The median platelet count increased from 7 × 10⁹ to 31 × 10⁹/L on day 3 (P < 0.01). The median decline in hemoglobin was 1.3 g/dl. Two children experienced minor fever and chills within 24 hr of treatment. Pain at the injection site was common but self‐limiting with no effect on activity level. These results suggest subcutaneous anti‐D IgG 50 µg/kg as an effective and well‐tolerated treatment option in childhood ITP. Pediatr Blood Cancer 2009; 53:1315–1317. © 2009 Wiley‐Liss, Inc.     

Neonatal allo-immune thrombocytopenia due to fetomaternal HPA-1 incompatibility of a homozygous HPA-1a mother and a homozygous HPA-1b father

We report a case of neonatal allo-immune thrombocytopenia due to fetomaternal human platelet antigen (HPA)-1 incompatibility. Anit-HPA-1b antibodies were detectable in maternal serum. Repeated treatment of the infant with high-dose IgG effectively raised platelet counts transiently, but the patient remained thrombocytopenic for more than 6 weeks. Serological and DNA analysis revealed that the mother was homozygous HPA-1a and the father homozygous HPA-1b     

Treating IgE‐mediated diseases via targeting IgE‐expressing B cells using an anti‐CεmX antibody

Targeting the IgE pathway is a clinically validated strategy for treating IgE‐mediated diseases. Omalizumab, an anti‐IgE antibody, which binds to free IgE and prevents the binding of IgE to FcεRI on mast cells and basophils has been approved for severe persistent allergic asthma and chronic spontaneous (idiopathic) urticaria. The therapeutic efficacy of anti‐IgE has also been reported in allergic rhinitis, allergic bronchopulmonary aspergillosis, latex allergy, atopic dermatitis, allergic urticaria, anaphylaxis, and others. Anti‐CεmX, which binds to membrane‐bound IgE (mIgE) on IgE‐switched B cells, lyses mIgE‐expressing B lymphoblasts and prevents the allergen‐induced generation of IgE‐producing plasma cells, offers an alternative mechanism of intervening with the IgE inflammatory pathway. Because anti‐CεmX does not bind to free IgE, it can modulate the IgE pathway regardless of the serum IgE levels in treated patients. These unique pharmacologic mechanisms potentially enable anti‐CεmX to provide different clinical utilities from anti‐IgE and serve as a therapeutic and a prophylactic in some IgE‐mediated diseases, which are not adequately treated with current medicine.     

Outcomes of renal transplant in patients with anti‐complement factor H antibody‐associated hemolytic uremic syndrome

Atypical HUS associated with anti‐CFH autoantibodies is an uncommon illness associated with high risk of progression to end‐stage renal disease. Disease relapses after transplantation, observed in one‐third cases, often lead to graft loss. We report four patients with anti‐CFH antibody‐associated HUS who underwent renal transplantation 16–62 months from initial presentation. Two patients each received organs from deceased and living‐related donors. Anti‐CFH antibody titers were monitored during the illness and following transplantation. All patients received two doses of IV rituximab before or after transplantation; three patient each received 1–2 g/kg of IV immunoglobulin or underwent 2–5 sessions of plasma exchanges. The use of therapeutic plasma exchange, IV immunoglobulin, and rituximab in two cases enabled two‐third reduction in anti‐CFH antibody titers before transplantation. At 5‐ to 26‐month follow‐up, all patients showed satisfactory graft function without recurrence of HUS. This is the first report of patients with anti‐CFH antibody‐associated HUS who underwent living‐related renal transplantation. Clearance of anti‐CFH antibody by therapeutic plasma exchange and adjuvant immunosuppression aimed at decreasing antibody levels may enable successful transplantation and recurrence‐free survival.     

Plasmapheresis‐resistant acute humoral rejection successfully treated with anti‐C5 antibody

Even if kidney graft survival has improved during the last decades, sensitized pediatric patients are an emerging problem. We describe a 17‐yr‐old male who lost his first graft due to chronic rejection becoming hyperimmunized (CDC PRA 99.61%). A desensitization protocol based on high‐dose IVIG, PP, and two Mabthera^® infusions was performed with minor response (CDC PRA post‐desensitization 80%). One month after his second non‐living transplant, he developed a biopsy‐proven AMR; post‐transplant immunological monitoring showed the presence of donor‐specific anti‐DQ5 antibodies (DSA, MFI 20.000). He received methylprednisolone pulses and 45 PP sessions without clinical response; eculizumab was then used to salvage a kidney undergoing severe PP‐resistant rejection. A biopsy performed after the fourth eculizumab infusion showed complete resolution of AMR. Eculizumab infusions were then continued for the first year post‐transplantation. Two yr after transplantation, graft function is stable. Anti‐C5 therapy may represent an effective therapeutic option in pediatric patients with PP‐resistant AMR.     

Autoimmune thyroiditis following HLA‐matched sibling hematopoietic stem cell transplantation for Wiskott‐Aldrich syndrome

WAS is a fatal X‐linked combined immunodeficiency syndrome, the only cures for which are HSCT or gene therapy. AID occur in up to 72% of patients with WAS who do not receive HSCT, likely arising secondary to impaired multilineage immune autoregulatory function; AITD is not typically seen. In this article, we describe the case of a male patient who underwent HLA‐matched HSCT for WAS at the age of 5 months, with his sister (a WAS carrier) acting as his donor and subsequently developed AITD 12 months post‐transplant, with marked elevation of antithyroid peroxidase antibody titer. His donor sister was subsequently found to have elevated antithyroid peroxidase antibody titer with increasing trend and normal thyroid function. Although several mechanisms exist by which our patient may have developed AITD, we suggest the transfer of autoreactive donor immune cells as the most plausible explanation.     

Donor‐specific anti‐HLA antibodies in pediatric renal transplant recipients with creeping creatinine: Prevalence,histological correlations,and impact on patient and graft survival

Donor‐specific anti‐HLA antibodies (DSA) causing CAMR are responsible for a high proportion of long‐term graft failures after RTX. We studied the prevalence of DSA in RTX children biopsied for creeping Cr, its relationship with NA, and patient and graft survival according to histopathology. Between 2008 and 2013, 92 children were biopsied at a median of 38 months post‐RTX. At biopsy, the prevalence of DSA was 49% and C4d 70%. NA rate was 45%, higher in adolescents (60%). Most frequent diagnoses were CAMR (72%) and interstitial fibrosis with tubular atrophy (IFTA) (28%). Forty‐five of 66 patients with CAMR (68%) had detectable DSA. Twenty‐one DSA‐negative patients with CAMR had histological damage (IFTA + C4d positivity). C4d was detected in 64 of 66 biopsies with CAMR. Recipients with IFTA alone had neither C4d, nor detectable DSA, and were adherent. Graft survival at five yr was 89% in patients with CAMR, 79% in those with CAMR + TCMR Banff I, 33% in those with CAMR + TCMR Banff II, and 96% in those with IFTA. ABMR and complement activation were frequent in children biopsied for creeping Cr. Recipients with DSA were more likely to be non‐adherent and have CAMR or CAMR + TCMR and worse graft survival.     

Application of an epitope‐based allocation system in pediatric kidney transplantation

Donor–recipient HLA mismatch remains a leading cause for sensitization and graft loss in kidney transplantation. HLA compatibility at an epitope level is emerging as an improved method of matching compared with current HLA antigen allocation. A novel epitope‐based allocation approach to prospectively exclude donors with high‐level mismatches was implemented for pediatric KTRs on the DD waiting list. Nineteen consecutive transplants were followed for 12 months, including eight DD KTRs listed with eplet exclusions, as well as three DD KTRs and eight LD KTRs without exclusions. KTRs with eplet exclusions had estimated GFR of 78.5 mL/min/1.73 m², no episodes of rejection, and time to transplant 6.55 months. HLA‐A, HLA‐B, HLA‐DR antigen mismatches were similar between all groups. KTRs with exclusions had significantly lower class II eplet mismatches (20.4) than the contemporary DD KTRs without exclusions (63.7) and DD KTRs transplanted in the preceding decade (46.9). dnDSAs were identified in two of eight DD KTRs with exclusions, two of three DD KTRs without exclusions and five of eight LD KTRs. Epitope‐based allocation achieved timely access to transplantation, low class II eplet mismatches, and low rates of dnDSAs in the first year. This strategy requires longer follow‐up and larger numbers, but has the potential to reduce anti‐HLA sensitization and improve both graft survival and opportunities for future retransplantation.