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

[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.

[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.

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.

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.

Platelet and neutrophil alloantigen genotyping in clinical practice

Immune responses to platelet and neutrophil alloantigens are involved in the pathogenesis of several clinical syndromes including: neonatal alloimmune thrombocytopenia (NATP), post-transfusion purpura (PTP), refractory responses to platelet transfusion, neonatal alloimmune neutropenia (NAN), transfusion-related acute lung injury (TRALI), and chronic benign autoimmune neutropenia of infancy. Initially, platelet alloantigens were only characterized serologically. Subsequently, they were localized to specific platelet surface glycoprotein structures and ultimately defined to the level of nucleic acid polymorphisms on platelet glycoprotein genes. These advances allowed the tools of molecular biology to be applied to typing for platelet alloantigens. The advantages of such typing methods include: 1) patient platelets are no longer required for the typing assays, and therefore, platelet types can be established on extremely thrombocytopenic samples (by using peripheral blood white blood cells [WBC]); 2) The genotyping methods eliminate the requirement for rare serologic reagents. A number of different genotyping methods have been developed. These include: restriction fragment length polymorphism (RFLP), sequence specific primers (SSP), and Dot-Blot hybridization. Clinical applications of this methodology include: determining the platelet genotype of fetuses at risk for NATP, in the diagnosis of PTP, and identifying causes of refractory responses to platelet transfusions. Analogous to platelet alloantigens, a limited number of neutrophil alloantigens can now be determined by molecular biologic methods. The new methods obviate the need to isolate fresh neutrophils for serologic typing and do not require rare serologic reagents. To date, molecular polymorphisms associated with alloantigens on the neutrophil Fc gamma RIIIb surface glycoprotein have been elucidated. These include the allo-antigens NA1, NA2, and SH.

Platelet alloimmunization after transfusion. A prospective study in 117 heart surgery patients

BACKGROUND AND OBJECTIVES

The frequency of platelet-specific antibodies after one series of blood transfusions has not been reported, and in multiply transfused patients is controversial.

MATERIALS AND METHODS

We studied the frequency of alloimmunization against platelet antigens in 117 patients who received a single series of blood transfusions. They received mostly saline-adenine-glucose+mannitol red blood cell components (poor in leukocytes and platelets) in connection with cardiac surgery. Platelet-specific antibodies were detected with the platelet ELISA and the monoclonal-antibody-specific immobilization of platelet antigen assay. HLA antibodies were detected by the standard lymphocyte cytotoxicity techniques.

RESULTS

We found platelet-specific anti-HPA-5b (anti-Bra) in 2 cases (1.7%). One antibody was the result of de novo immunization. We detected lymphocytotoxic HLA antibodies in 21 patients (17.9%), of whom 18 (15.4%) had had no detectable antibodies before transfusion. There was a positive correlation between the transfused load of immunogenic materials and the frequency of alloimmunization against HLA antigens. In one third of the immunized patients, there was no history of previous immunization.

CONCLUSION

There was a low incidence of platelet-specific antibodies after one series of blood transfusions in this group of patients. This is similar to the results of some previous studies in multiply transfused patients, but not with those of others who found a higher incidence.

Platelet-specific antibodies in transfused patients

Sera of 104 patients with haematological diseases, transfused with platelets and sometimes also with red cells, were prospectively investigated in: the lymphocytotoxicity test (LCT), the platelet suspension immunofluorescence test (PSIFT) and the monoclonal antibody immunobilization of platelet antigens (MAIPA) technique. All tests on admission were negative. The overall incidence of alloantibodies after transfusions was 30.8%. Platelet-specific antibodies were, however, detected much more rarely (9.6%) than anti-HLA (21.3%). The specificity against HPA antigens was defined in 4 (3.9%) patients: anti-HPA-la, 2b, 3a and 5b. In the remaining 6 (5.7%) cases only the glycoproteins on platelets were identified (GPIb and GPIIIa) which gave positive reaction with the antibodies. Our observations indicate a rather low incidence of platelet-specific antibodies after transfusions.