Identification of HLA class II antigens as the targets of effector clones which may cause transfusion-associated graft-versus-host disease

We established T cell clones, which were considered to be the possible cause of transfusion-associated graft-versus-host disease (TA-GVHD), from the peripheral blood lymphocytes (PBLs) of two patients. In both cases, several CD4⁺ cytotoxic T-cell (CTL) clones were established. In case I, the target antigen of the established CD4⁺ clones was a DRB1*0403-related antigen serologically typed as HLA DR4, which was one of the patient HLA antigens. In case II, the target of four out of five established CD4⁺ CTL was a DRB1*1302-related antigen. One CD4⁺ CTL clone showed cytotoxicity against cells carrying A*2402, B*4403, Cw*1403 and DPB1*0401. A monoclonal antibody (mAb) blocking study showed only anti-DP mAb inhibited the cytotoxicity of this clone. Thus, it might be considered that this clone recognizes HLA-DP with its binding peptides derived from either A*2402, B*4403, Cw*1403 or DRB1*1302. Our findings indicate that CD4⁺ CTLs may play important roles in the aetiology of TA-GVHD and that the antigens of patients recognized by donor-derived effector cells may not always recognize a single HLA antigen.     

Transfusion-associated graft-versus-host disease: risk due to homozygous HLA haplotypes

BACKGROUND: Transfusion-associated graft-versus-host disease (TA-GVHD) may occur in transfusions of blood from HLA-homozygous persons to HLA- heterozygous persons who share a haplotype. STUDY DESIGN AND METHODS: Two mathematical models were developed to calculate the upper and lower limit of the associated risks in various populations using a combination of serology- and DNA sequence-based HLA haplotype frequencies. RESULTS: For nondirected transfusion, the range of the estimated risk in United States whites is 1 of 17,700 to 39,000 (1/6,900-48,500 in Germans; 1/1,600-7,900 in Japanese). The risk in directed donation between parents and children is increased at least 21- fold for US whites, 18-fold for Germans, and 11-fold for Japanese. CONCLUSION: For nondirected transfusions, the estimates of TA-GVHD risk derived in this model are lower than estimates of previously published models, are in better agreement with the clinical experience, and explain in part the observed discrepancy between TA-GVHD incidence in the United States and that in Japan. Most notably for US whites, the relative increase in risk in directed transfusion is larger than previously thought.     

How does transfusion-associated graft-versus-host disease compare to hematopoietic cell transplantation-associated graft-versus-host disease?

Transfusion-associated graft-versus-host disease (TA-GVHD) is a rare life-threatening complication of blood transfusion caused by donor T cells that escape rejection by the recipient immune system. These donor T cells drive recipient tissue damage in response to host antigens. On the other hand, GVHD occurring after allogeneic hematopoietic cell transplantation (HCT-GVHD) is also caused by donor T cells, but its pathophysiology is more complex and differs due to the effects of tissue damage caused by pre?HCT conditioning and profound immunosuppression. Both TA-GVHD and HCT-GVHD can be fatal; however, mortality is higher with TA-GVHD due to the paucity of treatment options. Here, we compare and summarize the presentation, diagnosis, pathophysiology, prevention, and treatment of TA-GVHD and HCT-GVHD.     

HLA class I-eluted platelets as an alternative to HLA-matched platelets

BACKGROUND: Alloimmunized refractory thrombocytopenic patients often require HLA-matched platelet transfusions. As the HLA system is very polymorphic, sufficient HLA-matched donors are not available for every patient. STUDY DESIGN AND METHODS: In vitro elution techniques with citric acid incubation of platelets at pH 3.0 showed that platelets lose expression of HLA, whereas platelet-specific glycoproteins are preserved. This technique was modified for clinical use. Random-donor platelet concentrates were incubated with citric acid, subsequently washed, and transfused to two patients. RESULTS: Platelet-specific glycoproteins were unaffected, and HLA expression decreased generally to below 25 percent of the initial expression. One alloimmunized patient who was without compatible donors because of a rare HLA type underwent repeated transfusions with acid-treated platelets. In contrast to the results with random-donor platelet transfusions, posttransfusion increments up to 47 × 10(9) per L were obtained with acid-treated platelets, and profuse gastrointestinal bleeding was stopped, while multiple skin hemorrhages were resolved. No side effects were observed. A second patient developed a severe transfusion reaction without platelet increment after one transfusion with acid-treated platelets expressing 30 percent of the original HLA antigens. Further transfusions were not given. CONCLUSION: Standardization of the acid elution technique and validation of the technique in patients is necessary. The results suggest, however, that HLA-eluted platelets prepared under specified conditions may gain a place in platelet transfusion therapy.     

Screening for antibodies to HLA class I in apheresis donors following Covid‐19 or SARS-CoV-2 vaccination

Transfusion of HLA-specific antibodies may play a role in induction of TRALI, the transfusion complication responsible for most transfusion-related deaths. In Oslo, we screen our apheresis donors and defer HLA-immunized donors from donation of plasma-rich blood components. During the second year of the Covid-19 pandemic and following the first months of SARS-CoV-2 vaccination, both the virus itself and the vaccines were suspected of inducing de novo production of antibodies to HLA class I in patients. For the blood center, the possibility of finding HLA-antibodies in an increased number of blood donors has serious implications. We therefore conducted a study to map the extent of de novo HLA-specific antibodies in representative donor groups. 106 apheresis donors were screened for antibodies to HLA class I/II following Covid-19 or vaccination with either mRNA or adenovirus-vector vaccines, and the findings were compared to pre-Covid blood samples from the same donors. In addition, we analyzed pre-Covid samples from 11 HLA-antibody-positive donors of Covid convalescence plasma. Only three established thrombapheresis donors were deferred due to vaccine-induced HLA-antibodies. In short, our findings did not support the hypothesis that SARS-CoV-2 virus or vaccination cause de novo HLA immunization in healthy blood donors. However, some donors with pre-existing antibodies showed increased antibody expression, confirming a general boost of the immune response following infection or vaccination.     

Fatal graft-versus-host disease associated with transfusions of HLA- matched, HLA-homozygous platelets from unrelated donors

BACKGROUND : Transfusion-associated graft-versus-host disease (TA-GVHD) due to blood from HLA-homozygous related and unrelated blood donors has been described. CASE REPORT: Fatal TA-GVHD due to the transfusion of HLA-matched platelets from an unrelated HLA-homozygous donor is reported. A 61-year-old man with a history of diabetes mellitus and myelodysplastic syndrome was diagnosed with acute myelogenous leukemia in November 1991. Induction chemotherapy resulted in aplasia, which was followed by a normocellular marrow with mild dysplasia and continued karyotypic abnormalities. High-dose chemotherapy was given in a second attempt to achieve complete remission. HLA-matched platelets were ordered when platelet refractoriness developed. The patient was HLA- heterozygous for HLA-A and -B antigens (A2, 29; B37, 44). Over the next 7 days, four unirradiated HLA-matched plateletpheresis units were transfused; one was probably homozygous for both HLA-A and -B antigens (A2, -; B44, -) and was transfused first, and three were probably homozygous for an HLA-B antigen (A2, 29; B44, -) and were white cell reduced. No blood relatives served as donors. Seven days after the first HLA-matched platelet transfusion, fever, chills, and diarrhea developed; 2 days later, a rash was present. Liver enzymes increased markedly. Renal and respiratory failure ensured. A skin biopsy was consistent with GVHD. Despite immunosuppressive therapy, the patient died 19 days after the first HLA-matched platelet transfusion. CONCLUSION : TA-GVHD has been recognized in immunocompromised, HLA- heterozygous patients receiving blood from blood relatives who are HLA- homozygous. patients receiving blood from either blood relatives or non- blood relatives who are HLA-homozygous. This HLA-heterozygous patient received transfusions of unirradiated, class I HLA-homozygous platelets, which were specifically ordered as HLA-matched, and his death was attributed to TA-GVHD. Consideration should always be given to providing irradiated blood for immunosuppressed patients, especially when HLA-matched platelets are used, to prevent TA-GVHD.     

ELISA测定血清可溶性HLA—Ⅰ类抗原

目的　建立定量测定可溶性HLA I类抗原的ELISA方法。方法　测定上海地区汉族正常人群血清可溶性HLA I类抗原的含量 ,并进一步研究可能影响这一含量的因素。结果　测得 116例上海地区汉族正常个体血清可溶性HLA I类抗原的含量为 5 2 9 3 2±2 82 88ng/ml。结论　性别和常见HLA A位点抗原型别对血清可溶性HLA I类抗原的含量未造成显著影响。     

Association of I and II class HLA antigens with Cushing's syndrome]

Incidence of class I and II HLA antigens was studied in 69 patients suffering from Icenko--Cushing syndrome. Positive association was reported for antigens DRw53, DQw3, DR4, DR5, negative for antigen DR2. Antigen combinations DR5, DR7 and DR4, DR5 proved more prevalent. The risk to develop the disease rose 2-3-fold in case of HLA-DR5 phenotype occurrence with antigen DR4 or DR7. Association with DRw53 and DQw3 antigens showing wide specificity seemed most significant.     

Autoreactive T cell clones specific for class I and class II HLA antigens isolated from a human chimera

T cell clones of donor origin that specifically react with recipient cells were obtained from a SCID patient successfully reconstituted by allogeneic fetal liver and thymus transplantation performed 10 yr ago. The majority of these clones displayed both cytotoxic and proliferative responses towards PBL and an EBV-transformed B cell line derived from the patient. In addition, these T cell clones had proliferative and cytotoxic responses towards the parental PBL, EBV cell lines, and PHA blasts. Blocking studies with anti-class I and anti-class II HLA mAbs indicated that the activity of the CD4+ T cell clones was specifically directed against class II HLA antigens of the recipient. On the other hand, the cytotoxic and proliferative responses of the CD8+ T cell clones were specific for class I HLA antigens which are ubiquitously expressed on the recipient cells. Thus, the establishment of transplantation tolerance observed in this stable human chimera is not due to the elimination of host-reactive T cells from the repertoire and suggests the presence of a peripheral autoregulatory suppressor mechanism.     

Simple ELISA method for the evaluation of soluble HLA class I antigens in human serum

A simple sandwich ELISA method has been developed for the quantification of soluble HLA class I antigens (s-HLA) in human serum. The assay utilizes the monoclonal antibody Q6/64, directed to a monomorphic determinant of the HLA alpha-chain, to capture the antigen and the biotinylated NAMB1 monoclonal antibody, directed to beta 2-microglobulin, as the detection antibody. The extract of the LG-2 lymphoid cell line and pooled sera from 100 healthy subjects are utilized as standards. The arbitrary value of 100 s-HLA Relative Units/mL (RU/mL) is given to the 1:20 dilution of pooled human sera whose optical density value corresponds to the one of the extract of 1 x 10(6) LG-2 cells (6.25 micrograms/mL protein concentration). The assay is easy to perform, specific, reproducible (intra- and inter-assay variations ranging from 3.2% to 8.87%), sensitive (detection limit of 6 RU/mL), and needs a small amount of serum (0.1 mL). The mean serum levels of s-HLA found in 100 healthy normal subjects are 41.9 +/- 13.4 RU/mL. The potential uses of the method are discussed.     

HLA class I deficiencies due to mutations in subunit 1 of the peptide transporter TAP1

The transporter associated with antigen processing (TAP), which is composed of two subunits (TAP1 and TAP2) that have different biochemical and functional properties, plays a key role in peptide loading and the cell surface expression of HLA class I molecules. Three cases of HLA class I deficiency have previously been shown to result from the absence of a functional TAP2 subunit. In the present study, we analyzed two cases displaying not only the typical lung syndrome of HLA class I deficiency but also skin lesions, and found these patients to be TAP1-deficient. This defect leads to unstable HLA class I molecules and their retention in the endoplasmic reticulum. However, the absence of TAP1 is compatible with life and does not seem to result in higher susceptibility to viral infections than TAP2 deficiency. This work also reveals that vasculitis is often observed in HLA class I-deficient patients.     

Quantification of soluble serum HLA class I antigens in healthy volunteers and AIDS patients

A solid-phase enzyme immunoassay (ELISA) has been used to quantify human soluble Class I histocompatibility antigens in serum samples from voluntary blood donors and AIDS patients. Statistical analysis of the results showed significantly raised levels (p less than 0.01) of free HLA Class I in sera from AIDS patients (2.95 +/- 1.80 micrograms/ml) when compared with the blood donors (1.06 +/- 0.6 micrograms/ml). The assay is specific, reproducible and easy to perform. Potential uses of this determination are discussed.     

Expression of HLA class I antigens in human tumors and their involvement in tumor growth

Summary A decreased expression of major histocompatibility complex (MHC) class I antigens is a common feature of many experimental and human tumors and can often be correlated with malignancy grade. In fact, reduction of class I antigens is associated in most tumors with an enhanced ability to elude immune surveillance. Loss of HLA-A,B,C antigens ranges from a decrease in the percentage of A,B,C-positive cells to selective loss of particular antigens and total loss of class I molecule expression. In man, this has been documented in melanomas, carcinomas, lymphomas, neuroblastoma and acute leukemias. The reduction in membrane antigens is generally associated with a parallel fall in immunoprecipitable intracellular proteins and the corresponding mRNAs in the absence of structural changes in the coding genes. The literature concerning the above mentioned topics is reviewed and discussed. This work was supported in part byConsiglio Nazionale delle Ricerche (CNR), Roma, Italy,Progetto Finalizzato ‘Biotecnologie e Biostrumentazione’. T. Crepaldi was supported by a fellowship of ‘Comitato Gigi Ghirotti’.     

Opportunities and limitations of mouse models humanized for HLA class II antigens

Summary.  MHC class II molecules are essential for shaping the CD4+ T-cell repertoire in the thymus and for selecting antigenic peptides that are presented to CD4+ T cells in the periphery. A range of different mouse models humanized for HLA class II antigens have been developed to study the regulation of MHC-class II restricted immune responses. These mouse models have been used to identify immunodominant peptides that trigger diseases and to characterize the interactions of T-cell receptors with disease-associated peptides and MHC class II molecules. Peptides presented to CD4+ T cells in these mouse models were shown to be similar to peptides presented to CD4+ T cells in patients who carry the same MHC class II haplotype. Opportunities and limitations associated with these mouse models will be discussed and the potential application of these models for understanding the regulation of antibody responses against factor VIII in hemophilia A will be indicated.