Immune thrombocytopenia more than a year after allogeneic marrow transplantation due to antibodies against donor platelets with anti-PlA1 specificity: evidence for a host-derived immune reaction

Transplantation of encapsulated human Leydig-like cells: A novel option for the treatment of testosterone deficiency

Previous studies have demonstrated that the transplantation of alginate-poly-ʟ-lysine-alginate (APA)-encapsulated rat Leydig cells (LCs) provides a promising approach for treating testosterone deficiency (TD). Nevertheless, LCs have a limited capacity to proliferate, limiting the efficacy of LC transplantation therapy. Here, we established an efficient differentiation system to obtain functional Leydig-like cells (LLCs) from human stem Leydig cells (hSLCs). Then we injected APA-encapsulated LLCs into the abdominal cavities of castrated mice without an immunosuppressor. The APA-encapsulated cells survived and partially restored testosterone production for 90 days in vivo. More importantly, the transplantation of encapsulated LLCs ameliorated the symptoms of TD, such as fat accumulation, muscle atrophy and adipocyte accumulation in bone marrow. Overall, these results suggest that the transplantation of encapsulated LLCs is a promising new method for testosterone supplementation with potential clinical applications in TD.

[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.

Recurrence of monoclonal gammopathy associated with donor-derived myelodysplastic syndrome after cord blood stem cell transplantation

Myelodysplastic syndrome (MDS) is known to be associated with functional abnormalities of B cells, including hypergammaglobulinemia and monoclonal gammopathy (MG). However, the pathogenesis of these immunological disorders has not been clarified. We report a patient who developed donor-derived MDS followed by leukemic transformation after cord blood transplantation for MDS with MG. Interestingly, MG reappeared before development of donor-derived MDS. We analyzed the immunoglobulin allotype gene polymorphisms to determine whether the MG after cord blood transplantation was of recipient origin or donor origin. Results of genetic analysis and enzyme-linked immunosorbent assay of IgG1 allotype revealed that the MG after cord blood transplantation was of donor origin. Although the mechanism of donor-derived MG remains unclear, the persistent presence of recipient's antigen presenting cells might have induced the abnormal immunoglobulin production.

[Occurrence of severe, persistent thrombocytopenia following allogeneic bone marrow transplantation, attributable to anti-HPA-1 allo-immunisation of the host]

A 56 year-old, multiparous woman suffering from a myeloproliferative syndrome, who had received multiple red blood cell and platelet transfusions, was the recipient of an allograft of peripheral blood stem cells derived from her HLA-A, B, DR, DQ and DP and ABO identical sister, following myeloablative conditioning. The persistence of severe, isolated thrombopenia resistant to platelet transfusions led to the discovery of anti-HLA class I allo-immunisation. As HLA compatible platelet transfusions did not result in satisfactory platelet increments, we then discovered the simultaneous presence of anti-HPA-1a allo-immunisation. Genotyping of the HPA-1 systems of the patient (HPA-1B/B) and her sister (HPA-1A/B) enabled us to elucidate the mechanism underlying the persistent thrombopenia and the inefficacy of transfusion. In fact, only transfusion of HPA-1B/B platelets (HLA compatible or incompatible) proved to be efficacious. To reduce the level of anti-HPA-1a antibodies, we performed plasmapheresis sessions and used an anti-CD20 monoclonal antibody. It was only on achieving total haematopoietic chimerism, through rapid interruption of the immunosuppression, that we obtained spontaneous normalisation of the platelet count. The present case emphasises the necessity, before undertaking any allograft of haematopoietic stem cells - even if the latter come from a strictly HLA identical member of the family - of performing a search for eventual anti-HPA allo-immunisation.

Prolonged thrombocytopenia after allogeneic hematopoietic stem cell transplantation: associations with impaired platelet production and increased platelet turnover

To evaluate the mechanisms underlying prolonged thrombocytopenia after allogeneic hematopoietic stem cell transplantation (SCT), an index for plasma glycocalicin normalized for the individual platelet count (GCI), plasma thrombopoietin (TPO), and circulating B cells producing anti-GPIIb-IIIa antibodies were measured in 50 SCT recipients with or without prolonged thrombocytopenia, 42 patients with idiopathic thrombocytopenic purpura, nine patients with aplastic anemia, and 22 healthy individuals. All three indices were significantly higher in the SCT recipients with thrombocytopenia than in those without (P < 0.01 for all comparisons), and were significantly correlated with the platelet count in SCT recipients. Stepwise multiple regression analysis of the samples from the SCT recipients revealed that GCI and TPO independently pointed to specific mechanisms of thrombocytopenia. The GCI and TPO status in SCT recipients with thrombocytopenia had a pattern similar to that seen in aplastic anemia, suggesting a major role for impaired thrombopoiesis. An antiplatelet antibody response was frequently detected in SCT recipients, but the development of thrombocytopenia is likely to depend on additional factors, such as reticuloendothelial function. In summary, post transplant prolonged thrombocytopenia is associated with complex mechanisms, including impaired thrombopoiesis and increased platelet turnover.

Severe thrombocytopenia due to host-derived anti-HPA-1a after non-myeloablative allogeneic haematopoietic stem cell transplantation for multiple myeloma: a case report

BACKGROUND AND OBJECTIVES

Host- or donor-derived alloimmune thrombocytopenia can develop after non-myeloablative allogeneic haematopoietic stem cell transplantation (HSCT). We report the first case of host-derived HPA-1a antibodies.

CASE REPORT

A 52-year-old male patient received HSCT from his human leucocyte antigen (HLA)-A, -B, -C, -DR identical brother after reduced intensity conditioning. Bilinear engraftment around day 12 was accompanied by a continuous decrease of platelet counts. We investigated for platelet antibodies because of a progressive decline of platelet counts and refractoriness to platelet transfusions.

METHODS

The patient's serum was tested by enzyme-linked immunosorbent assay (ELISA), a solid phase assay and monoclonal antibody-specific immobilization of platelet antigens (MAIPA) assay. Recipient's DNA from the time before HSCT and donor's DNA were genotyped for human platelet antigens.

RESULTS

Serum obtained on day 15 after HSCT reacted strongly with the donor's platelets due to host-derived anti-HPA-1a- and anti-HLA I antibodies. Serum samples from days 39, 45 and 65 after HSCT contained only anti-HLA I; no antibodies were detectable on day 149. Platelet counts increased on day 20 spontaneously. The decrease of the antibodies accompanied by the increase of the platelet counts suggests progressive elimination of residual host cells.

CONCLUSIONS

The HPA-1a antibodies affected thrombopoietic engraftment and the success of platelet transfusions.

The influence of human platelet antigen match on the success of allogeneic peripheral blood progenitor cell transplantation following a reduced-intensity conditioning regimen

BACKGROUND

Allogeneic transplantation in elderly patients requires a dose-reduced conditioning regimen. Owing to reduced-intensity conditioning, host- and donor-type immune responses may affect the early posttransplant period, whereas only later on donor-derived reactions may ensue. Mismatches in the HLA system are known to be detrimental for the outcome of transplantation. Mismatches between donor and recipient for human platelet antigens (HPAs) may also affect the success of transplantation owing to serving as minor histocompatibility antigens and therefore rendering recipients at risk for graft-versus-host disease (GVHD) or graft rejection and inhibition of thrombopoiesis attributed to platelet (PLT) antibodies.

PATIENTS AND METHODS

Therefore, the occurrence of GVHD, incidence of relapse, need of PLT support, and outcome by analysis of 45 donor-recipient pairs for HPA-1, -2, -3, and -5 allotypes and screening for PLT antibodies were evaluated before transplantation and again 1 year thereafter.

RESULTS

Mismatches within the HPA system were not associated with an increased occurrence of transplant-related mortality or GVHD, the onset of thrombopoiesis, the frequency of PLT transfusions, or the incidence of relapse. Neither were settings of homozygous donors versus heterozygous recipients (graft-vs.-host direction) nor homozygous recipients versus heterozygous donors (host-vs.-graft direction) associated with any adverse effects on the outcome of the transplantation.

CONCLUSION

Thus, the HPA match does not affect the outcome of transplantation after reduced-intensity conditioning.

Human platelet antigen systems in allogeneic peripheral blood progenitor cell transplantation: effect of human platelet antigen mismatch on platelet engraftment and graft-versus-host disease

BACKGROUND

Alloimmune incompatibility in allo-geneic stem cell transplantation (ASCT), pregnancy, and blood transfusion might trigger an immune response with clinical consequences. Human PLT antigens (HPAs), which play a significant role in pregnancy or blood transfusion-associated alloimmune thrombocytopenia, are also expressed on the surface of tissues affected by GVHD. Thus, HPA mismatch in HLA-identical ASCT could play a potential role in PLT engraftment and GVHD.

STUDY DESIGN AND METHODS

We studied the HPA-1, -2, and -5 genotypes in Caucasian donors and patients involved in 77 HLA-identical ASCTs. We evaluated the association of HPA compatibility with clinical outcome, analyzing the relevance of host-versus-donor HPA incompatibility in PLT engraftment and donor-versus-host HPA incompatibility in GVHD.

RESULTS

PLT engraftment and transfusion require-ments were similar in HPA-compatible and HPA-incompatible ASCT. Cases with severe thrombocytopenia or significant delayed PLT engraftment did not display host-versus-donor HPA incompatibility. Moreover, the incidence of GVHD did not correlate with HPA compatibility.

CONCLUSION

Our results support no role for these antigens in immune complications of ASCT: PLT engraftment, requirement of PLT transfusions, and GVHD.

Alloimmune thrombocytopenias

Alloimmunization against platelet antigens may take place during pregnancy and following transfusion or transplantation. The resulting antibodies bind to the target platelet antigens and may lead to a rapid sequestration of incompatible platelets. The alloimmune thrombocytopenias are classified into neonatal alloimmune thrombocytopenia, post-transfusion purpura, passive alloimmune thrombocytopenia, transplantation-associated alloimmune thrombocytopenia, and platelet transfusion refractoriness. Neonatal alloimmune thrombocytopenia occurs in roughly one of 1,000 births and is the most important type in children. The management of affected infants during pregnancy is yet not established, and the most rapidly effective treatment after delivery is the transfusion of compatible platelets.

Influence of human platelet antigen match on the success of stem cell transplantation after myeloablative conditioning

Mismatches between donor and recipient for human platelet antigens (HPA) may affect the success of transplantation due to: (a) serving as minor histocompa-tibility antigens and therefore render recipients at risk for graft-versus-host disease (GvHD), (b) inhibition of thrombopoiesis due to platelet antibodies. We therefore evaluated the occurrence of GvHD and need of platelet support by prospective analysis of donor-recipient pairs (n=53) for HPA-1, -2, -3, and -5 allotypes and screening for platelet antibodies prior to transplantation and in weekly intervals until day 100 after transplantation. Neither the incidence of GvHD nor the onset of thrombopoiesis, nor the CCI after platelet transfusions, nor the frequency of platelet transfusions was affected by HPA mismatches. Settings of homozygous donors vs heterozygous recipients or homozygous recipients vs heterozygous donors were not associated with any adverse effects on the outcome of the transplantation. Thus, the HPA-match does not affect the success of transplantation.

PCR with sequence-specific primer-based simultaneous genotyping of human platelet antigen-1 to -13w

BACKGROUND

Accurate human platelet antigen (HPA) typing is important for patients with diagnosis of alloimmune thrombocytopenic syndromes and provision of HPA-matched blood components for these patients.

STUDY DESIGN AND METHODS

Thirteen sequence-specific primers (SSPs) designed on the basis of known published polymorphisms for HPA-1 to HPA-13w, respectively, were employed for simultaneous HPA genotyping. All PCR amplifications were carried out with identical cycling conditions in 96-well plates containing primer mixtures. A total of 300 blood samples from unrelated volunteer donors in Taiwan were included in the study.

RESULTS

All primers had specific amplification products. The typing results were available within 4 hours each time for up to four blood samples tested. Among the 13 HPAs, HPA-3 had the greatest heterozygosity with a gene frequency of 0.3267, 0.4967, and 0.1767 for HPA-3a/HPA-3a, HPA-3a/HPA-3b, and HPA-3b/HPA3-b, respectively. For the remaining 12 HPAs, the predominance of a/a homozygosity was noted for HPA-1, -2, -4, -5, and -6, with a frequency ranging from 0.9200 to 0.9967. The frequency of a/a homozygosity was 1.0000 for HPA-7w to -13w, except for HPA-10w, for which one case was observed to be HPA-10aw/HPA-10bw heterozygous. Excluding HPA-3, b/b homozygosity was noted in only one case (HPA-6b/HPA-6b). The prevalence rates of HPA-1 to -13w in this study were consistent with previous reports using different methods.

CONCLUSION

An extended, streamlined PCR-SSP protocol for simultaneous genotyping of HPA-1 to HPA-13w was established. This allows fast and reliable diagnosis of alloimmune thrombocytopenia, and is readily applicable to large-scale genetic population studies.

B-lymphoblastoid cell lines as a source of reference DNA for human platelet and neutrophil antigen genotyping

BACKGROUND

Human platelet and neutrophil antigens (HPAs, HNAs) are targets for platelet or granulocyte antibodies causing immune thrombocytopenia or neutropenia, respectively. Currently, genotyping is replacing phenotyping as the preferred method of diagnosis of immune cytopenia. To establish a reliable genotyping analysis, however, the availability as reference DNA of genomic DNA from persons of known genotype is essential.

STUDY DESIGN AND METHODS

By the use of Epstein-Barr virus transformation, panels of B-lympho-blastoid cell lines (B-LCLs) from HPA- and HNA-phenotyped individuals were developed. Genomic DNA was isolated from these cell lines and tested as reference DNA for genotyping of persons for HPAs and HNAs.

RESULTS

DNA derived from these B-LCLs was typed by polymerase chain reaction-restriction fragment length polymorphism and -sequence-specific primers. The results were in accordance with the genotyping from peripheral blood cells. These results were confirmed by 24 laboratories in Germany in a blind study.

CONCLUSION

The inexhaustible source of reference DNA derived from B-LCLs allowed the evaluation of reliable HPA and HNA genotyping for quality control purposes. It should facilitate the development of DNA typing in blood centers and clinical laboratories.

Clinical aspects and typing of platelet alloantigens

Platelet alloantigens can induce the formation of corresponding alloantibodies when exposed to phenotypically negative individuals. These antibodies are responsible for fetal and neonatal alloimmune thrombocytopenia, posttransfusion purpura, passive alloimmune thrombocytopenia and transplantation-associated thrombocytopenia and may contribute to platelet transfusion refractoriness together with HLA antibodies. Besides antibody detection laboratory diagnosis of the clinical syndromes requires alloantigen typing. Furthermore, typed platelet donors are a prerequisite for effective platelet transfusion therapy. Different techniques for phenotyping are well established and easy to perform but they rely on the availability of antisera. Since the molecular genetic background of the clinically most relevant alloantigens has been elucidated during the last years various genotyping methods have been applied to the platelet membrane polymorphisms and thus facilitated widespread platelet alloantigen typing. Generation of antibodies from phage display libraries and of lymphoblastoid cell lines from donors with all genetic variants will allow further developments.

Maternal immunization to Gov system alloantigens on human platelets

BACKGROUND

Immunization to platelet alloantigens can occur during pregnancy or after the transfusion of blood components. Platelet alloantibodies can cause neonatal alloimmune thrombocytopenia and posttransfusion purpura. Transfusion-induced alloimmunization to a novel platelet alloantigen system, Gov, expressed on the 175-kDa glycosyl phosphatidylinositol-anchored platelet glycoprotein, CD109, was previously described. This report describes three unrelated patients who were alloimmunized to Gov(a) or Gov(b) during pregnancy.

STUDY DESIGN AND METHODS

Platelets were typed by using radioimmunoprecipitation for HPA-1a, -3a, -5a, -5b, Gov(a), and Gov(b) and by polymerase chain reaction-restriction fragment length polymorphism for HPA-1a, -1b, -3a, and -3b. Maternal sera were screened for platelet antibodies by using radioimmunoprecipitation and the antigen capture assay.

RESULTS

Patients 1 and 2 were investigated after the diagnosis of neonatal alloimmune thrombocytopenia in their children, and alloantibodies specific for Gov(b) and Gov(a), respectively, were detected in maternal serum. Serum from patient 3, who had mild idiopathic thrombocytopenia purpura with no detectable autoantibody, was found to contain alloantibodies to Gov(b) and to HPA-5b, presumably as a result of immunization during pregnancy. Platelet typings confirmed that the patients were at risk for alloimmunization to the respective antigen.

CONCLUSION

This report of three cases of maternal alloimmunization to antigens in the Gov system indicates that immunization can occur via placental transfer of antigen and that Gov system alloantibodies may be associated with neonatal alloimmune thrombocytopenia.

Megakaryocytes and platelets in immune thrombocytopenic purpura

In idiopathic thrombocytopenic purpura, 90% of the patients have an elevated platelet-associated immunoglobulin. The most important related antigens are glycoprotein IIb-IIIa (GPIIb-IIIa) (16.7-83.3%), GPIb-IX (13.3-83%), GPIb (3.3-47.1%) and GPIIIa (21.6-33.3%), and less commonly GPIa-IIa, GPIV and GPV. Other related antigens can be platelet granule membrane protein, phospholipid, intraplatelet and cytoplasmic antigens, and rarely human platelet antigen (HPA) 1a and HLA-DR antigens. The marrow megakaryocytes are usually normal or increased in number with maturation impairment. There are discrepancies regarding megakaryocytopoiesis in vitro. A low dose of heparin could elevate the platelet number in certain cases. The expression of c-sis was reported to be inhibited in ITP, when the plasma beta-thromboglobin-platelet factor 4 level was elevated. In secondary immune thrombocytopenia, platelet antibodies can be (1) alloantibodies against the (HPA) system and (2) autoantibodies most commonly against platelet GPIIb-IIIa or GPIb-IX. Other antigens can be 30-52kDa proteins of the platelet membrane. Platelet survival is usually shortened, and marrow megakaryocytes are normal in number. Megakaryocyte colony-forming units could be reduced.

Graft-derived anti-HPA-2b production after allogeneic bone-marrow transplantation

We report on a male who received a bone-marrow allograft from his HLA identical sister for acute myelogenous leukaemia. After transplantation, the patient suffered from refractoriness to the transfusions of HLA-matched platelets and a strong platelet-specific antibody, anti-HPA-2b, of IgG1 subclass was demonstrated in the patient's serum. In the serum of the bone-marrow donor a weak IgG1 anti-HPA-2b was demonstrated. IgG allotyping of the patient and donor showed identical results. We could not determine the origin of the anti-HPA-2b, although we hypothesize that the anti-HPA-2b was produced by immunocompetent donor lymphocytes infused with the suspension of bone-marrow cells.

Late onset immune pancytopenia following bone marrow transplantation

A 17-year-old boy developed autoimmune pancytopenia in the absence of chronic graft-versus-host disease 170 d after allogeneic bone marrow transplantation (BMT) from his HLA identical brother. The anaemia and thrombocytopenia responded to conventional immunosuppressive treatment, but the neutropenia was refractory to this and to splenectomy and subsequent removal of splenic remnant. Following total lymphoid irradiation the neutrophil count rose to low normal levels but thrombocytopenia and anaemia secondary to marrow hypoplasia required transfusion support. Bone marrow function was finally normalized by an additional transfusion of donor marrow without prior immunosuppressive therapy. We conclude that late onset immune pancytopenia post BMT caused by antibodies of probable donor origin may be life threatening in the absence of chronic graft-versus-host disease.