Evidence of involvement of cytotoxic antibodies directed against patient’s HLA class II produced by transfused donor-derived B cells in post-transfusion graft-versus-host disease

Post-transfusion graft-versus-host disease (PTGVHD) is one of the most severe side-effects of blood transfusion. To characterize the effector cells causing this disease, we cloned lymphocytes from a PTGVHD patient’s peripheral blood. T-cell and B-cell clones were established, the origins of which were proven to be transfused donor lymphocytes. It was found that the B cells produced IgG that mediated complement-dependent cytotoxicity to the cells bearing the patient’s HLA class II genotype. Our results suggest, for the first time, the involvement of B-cell-produced cytotoxic antibodies directed against patient’s HLA class II in the pathogenesis of PTGVHD.     

Establishment of a T-Cell Line from Lymphocytes Presumably Implicated in Posttransfusion Graft-versus-Host Disease

Posttransfusion graft-versus-host disease (PTGVHD) is known to develop in immunocompetent patients exhibiting clinical symptoms such as erythroderma, fever, liver dysfunction, diarrhea and pancytopenia. It is speculated that transfused blood donors' lymphocytes might recognize the recipients' HLAs as alloantigens. The thus stimulated lymphocytes might proliferate, expand and finally attack the host's immune system or tissues. However, details regarding these expanded donor cells such as: (1) whether they represent one clone or more, (2) the composition of lymphocyte subsets, and (3) the target HLA antigens of recipients, are not clear, since T-cell lines derived from PTGVHD patients have not yet been obtained. The aim of this study is to characterize T-cells responsible for PTGVHD and to identify their target molecules. For that purpose, we attempted to establish T-cell lines derived from a PTGVHD patient. We show that the established T-cell line, proven to be derived from donor lymphocytes, showed a CD4+ phenotype and had cytotoxic activities. Furthermore, we describe that the target of the cytotoxic T-cell line (CTL) is an HLA-DRBl*0405-related molecule of the patient.     

Flow-cytometric approach to the prompt laboratory diagnosis of TRALI: a case report

OBJECTIVES: Transfusion-related acute lung injury (TRALI) is a rare but serious complication which can occur after transfusion of blood components. In this report we describe our flow-cytometry approach to the laboratory diagnosis of a case of TRALI in a recipient of fresh frozen plasma containing human leukocyte antigen (HLA) class II antibodies. METHODS: The post-transfusion reaction work-up included the direct and indirect Granulocyte Immunofluorescence Test (GIFT) on the recipient's neutrophils collected before and after the reaction and on the serum from the recipient and from all implicated donors; flow-cytometry bead-based screening and identification assay for HLA class I and II antibodies in donor sera and flow cytometry cross-matching on T and B patient's lymphocytes. Finally, we investigated the reactivity of one donor serum, containing HLA class II antibodies, with the patient's neutrophils activated in vitro to induce expression of HLA class II. RESULTS: We found an increased level of IgG bound on patient's granulocytes collected after TRALI, in the absence of detectable granulocyte and HLA class I antibodies in the five implicated donors. One of them showed HLA-DR 1 and -DR 51 antibodies, which determined a positive cross-match with patient's B lymphocytes and in vitro activated granulocytes. Both HLA class II antigens were present in the recipient and absent in the donor. CONCLUSIONS: In some pathological conditions, HLA class II antibodies can react with activated granulocytes expressing HLA-DR antigens, and activate TRALI reaction. HLA class II antibodies screening and flow cytometry cross-matching techniques should be added to the current diagnostic algorithm of TRALI.     

Transfusion-Associated Graft-versus-Host Disease in an Immunocompetent Patient following Cardiac Surgery

Objectives: We determined which of the 22 blood components obtained from unrelated donors and transfused to an apparently immunocompetent patient following open heart surgery caused transfusion-associated graftversus-host disease (TA-GVHD). Methods: Serologic and molecular methods were used to type the donors, the patient's family members, and the patient's postmortem tissues for HLA and a genetic marker on chromosome 17. Results: Two donors were homozygous for the HLA class I antigens A1 B8, for which the patient was heterozygous. Both donors were heterozygous, not homozygous as expected, for the class II alleles. One of them had the same class II alleles as the patient (DRB1*0301, DRB3*0101/DRB1*0404, DRB4*0103). The patient's tissues were chimeric for restriction fragments at 17 p 13 of this donor. Conclusion: One-way HLA match leading to TA-GVHD can be caused by donor blood that is homozygous for class I and heterozygous for class II alleles. Two blood components given to our patient had such one-way HLA match. Class II alleles of the lymphocytes in one component were identical with those of the recipient and caused TA-GVHD. Class II alleles of the lymphocytes in the other component differed from those of the recipient and were eliminated either by the immune system of the patient or the lymphocytes that caused the TA-GVHD (graft versus graft).     

Fatal graft-versus-host disease following blood transfusion in Hodgkin's disease documented by HLA typing

Fatal graft-versus-host disease (GVHD) developed in a patient with Hodgkin's disease treated with combined chemotherapy and radiotherapy following the transfusion of 2 U of packed red blood cells. Clinical features of the GVHD included the development of exfoliative dermatitis, progressive hepatic dysfunction, aplastic anemia, and finally progressive fatal pneumonia. GVHD was documented by skin biopsy and chimerism by HLA typing. The HLA phenotype of the patient's skin fibroblasts [A3, Bw44 (w4)/A2, B15 (w4)] was appropriate for parental haplotypes and probably represented her true HLA phenotype. Lymphocytes from the patient (peripheral blood and lymph node biopsy) were of a different HLA phenotype (A3; Bw35, w38, w4, w6; Cw4), which was inappropriate for parental HLA haplotypes but identical to the HLA phenotype of one of the blood donors. The HLA-DR typing of the patient's family and of the blood donor demonstrated that the patient and the donor probably were HLA-DR identical (DRw5/DRw6), although no B lymphocytes could be obtained from the patient for direct DR typing. We are currently irradiating all blood products administered to patients with Hodgkin's disease receiving intensive treatment. Further observations will be necessary to determine whether transfusions to other cancer patients with immunodeficiency states should be restricted to irradiated blood products.     

The Development and Application of HLA Tetramers in the Detection, Characterization and Therapy of Type 1 Diabetes Mellitus

Islet antigens are presented by human leukocyte antigen (HLA) class I and II molecules and are recognized by CD8(+) and CD4(+) autoreactive T cells in type 1 diabetic individuals. Early identification of individuals at risk for the disease by detection of these antigens and the autoreactive cells themselves is essential for understanding pathogenesis and for intervention at an early stage to prevent ongoing beta-cell destruction. However, the methods of identifying autoimmune development at an early stage have appeared to be limited because of the heterogeneity of the disease. The appearance of autoantibodies in preclinical type 1 diabetes mellitus (T1DM) does not follow specific patterns and depends on patient characteristics such as age. Also, results obtained with cytokine assays revealed that the number of islet antigen-responsive T cells present in the pool of peripheral blood mononuclear cells (PBMC) of non-diabetic individuals is highly variable and can be similar to that assayed in diabetics. Therefore, new identification and detection methods are needed. In this context, the use of HLA epitopes to generate stable HLA epitope tetramers has recently proved to be a promising approach to the detection of autoreactive T cells in antigen-stimulated PBMC cultures from diabetic and pre-diabetic subjects. HLA class II tetramers have been found to be capable not only of detecting TCRalphabeta of different avidities for a common ligand, e.g. GAD65(555-567(mimitope)), but also of inducing apoptosis in lymphocytes with high TCRalphabeta avidity for this ligand. This observation even opens up a potential application of HLA class II tetramers as therapeutic agents for immune intervention in T1DM.     

Human leucocyte antigen-Cw-specific cytotoxic T lymphocytes generated from naive cord blood used for cord blood stem cell transplantation

Human leucocyte antigen (HLA)-Cw-reactive cytotoxic T lymphocytes (CTL) were generated from cord blood (CB) lymphocytes of two cases used for cord blood stem cell transplantation (CBSCT). In both cases, the CTL were cytotoxic against the patient's leukaemic cells, as well as the patient's Epstein-Barr virus (EBV)-lymphoblastoid cell line (EBV-LCL) and phytohaemagglutinin blasts, and the cytotoxicity was blocked by anti-HLA-class I monoclonal antibodies. In the first case, the CTL recognized Cw 3 (Cw 9 and Cw 10)-positive EBV-LCL, while in the second case, the CTL recognized Cw1 and/or Cw7. These cases suggest that CB T cells may be competent enough for generating CTL to induce a graft-versus-leukaemia effect and/or graft-versus-host disease in patients with CBSCT and that the mismatching of Cw antigens between patient and CB may be related to the outcome of CBSCT.     

Immunologic effects of human peripheral and intrathyroidal lymphocytes on xenotransplanted human thyroid tissue in athymic nude mice.

T cells are intimately involved in the etiology and pathogenesis of human autoimmune thyroid disease. In order to further elucidate the immunologic mechanisms leading to Graves' disease (GD), we investigated the effects of human lymphocytes derived from patients with autoimmune and nonautoimmune thyroid diseases on human thyroid tissue xenotransplanted into nude mice. Eight weeks after transplantation of thyroid tissue from 26 patients with nonautoimmune thyroid disease (nontoxic nodular goiter [NTG]) into nude mice, peripheral (PBL) and intrathyroidal lymphocytes (ITL) from 14 patients with NTG and 12 patients with GD were engrafted into the animals. ITL and PBL subsets were analyzed by flow cytometer before engraftment. Two days after lymphocyte engraftment, the thyroid transplants were examined histologically (HE) as well as immunohistologically by staining with monoclonal antibodies directed against CD3 (T-cell activation and signal transduction), immunoglobulin G (IgG), HLA class II and CD31 (human endothelium). After injection of GD lymphocytes, thyroid transplants contained significantly more CD3, HLA class II, and CD4 expressing cells. Engrafted PBL and especially ITL from patients with GD specifically migrated into human thyroid transplants but not into the mouse thyroids, induced expression of class II products and led to IgG production by plasma cells. Persistence of human endothelium has been proven by positive CD31 staining. In conclusion, our data demonstrate that an organ-specific immune response is induced only by GD lymphocytes that migrate specifically into the thyroid transplants. Persistence of human endothelial cells in the transplants suggests that homing in this in vivo model reflects the situation in GD patients.     

The DBY gene codes for an HLA-DQ5-restricted human male-specific minor histocompatibility antigen involved in graft-versus-host disease

Graft rejection or graft-versus-host (GVH) disease after HLA-identical stem cell transplantation is the result of recognition of minor histocompatibility antigens (mHags) by immunocompetent T lymphocytes from recipient or donor origin, respectively. Cytolytic T lymphocyte (CTL) clones can be isolated during graft rejection and GVH disease to identify mHags and their corresponding genes. Thus far, all human mHags identified appeared to be HLA class I-restricted. Here, we report the characterization of the first human HLA class II-restricted sex-linked mHag involved in GVH disease. Previously, we isolated an HLA-DQ5-restricted CD4(+) CTL clone from a male patient with chronic myeloid leukemia who developed acute GVH disease grade III-IV after transplantation of HLA genotypically identical female stem cells. Using a panel of female HLA-DQ5(+) EBV cells that we stably transfected with Y chromosome-specific genes, we determined that the HLA class II male-specific mHag (H-Y) was encoded by the Y chromosome-specific gene DBY. The H-Y epitope was localized in the DBY protein using female HLA-DQ5(+) peripheral blood mononuclear cells loaded with DBY protein fragments. The minimal peptide sequence leading to maximal recognition by the specific HLA-DQ5-restricted CTL clone was characterized as the 12-amino acid sequence HIENFSDIDMGE. Although the epitope differed by 3 amino acids from its X-homolog DBX, only 2 polymorphisms were shown to be essential for recognition by the CTL clone.     

Postoperative erythroderma with change of HLA phenotypes from heterozygotes to homozygotes: a report of two cases.

Fatal "postoperative erythroderma" (POE) developed in 2 patients treated with liver lobectomy and the transfusion of fresh blood. Their clinical features and skin-histological findings were indicative of acute graft-versus-host disease (GVHD). The HLA phenotypes of circulating lymphocytes of the 2 patients were heterozygous but became homozygous late in the clinical course and were identical with those of the blood donors. One of the patient's haplotypes was identical with the donor's homozygous haplotype. These findings suggest the mechanism of development of POE in apparently immunocompetent patients. The donor's T lymphocytes are histocompatible with the patient's tissues, are not rejected, and become engrafted. The patient's tissues are not histocompatible with the donor's, so that GVHD develops.     

HLA Antigens on Leukocyte Fragments and Plasma Proteins: Prestorage Leukoreduction by Filtration

HLA alloimmunization following blood transfusion results from recipient exposure to donor alloantigens. Numerous studies have documented that intact donor leukocytes are capable of provoking primary alloimmunization and that leukoreduction can decrease the incidence of primary HLA alloimmunization. HLA antigens also exist in soluble form and are present on leukocyte cell fragments. We measured the concentration of soluble HLA class I antigen in both standard and leukoreduced blood components during storage. Although the concentration of soluble class I HLA protein varied widely among different individuals, the concentration was stable during refrigerated storage of red cell concentrates and was not affected by leukocyte reduction by filtration. We also investigated whether or not HLA antigens present on leukocyte fragments were capable of stimulating either resting or in-vitro-primed lymphocytes in the mixed lymphocyte reaction (MLR). Leukocyte fragments prepared by repeated freeze-thaw were found to express both class I and class II HLA antigens, but fragments were not able to stimulate in primary or secondary MLR even in cultures supplemented with recombinant interleukin-2. These studies provide in vitro evidence to support the hypothesis that HLA antigens are not shed from intact cells to soluble forms during storage and that HLA alloantigens on cell fragments do not elicit a cellular immune response.     

Cocultures of human thyroid monolayer cells and autologous T cells: impact of HLA class II antigen expression

Normal human thyroid cells in monolayer culture were induced to express surface HLA class II antigens (DR and DQ) by lectin stimulation. HLA class II positive thyroid cells caused proliferation of autologous T cells, a phenomenon not found in the absence of detectable HLA class II antigen expression. Autologous T cell proliferation was further stimulated by the presence of lectin-free interleukin-2, a known stimulator of activated T cells, and inhibited by monoclonal antibody to HLA-DR antigen. These data demonstrated that normal human thyroid cells, following HLA class II antigen expression, have the capacity to stimulate the immune system. Since over 90% of the monolayer cells were thyrocytes, based on staining with antithyroid microsomal serum, and cells of the monocyte/macrophage series were absent, it is suggested that HLA class II antigen positive human thyroid cells were the principal activators of autologous T cells. Such a mechanism may be important in the target site amplification of human autoimmune thyroid disease in susceptible individuals.     

Detection of monoclonal B lymphocytes in bone marrow and peripheral blood of multiple myeloma patients by immunoglobulin gene rearrangement studies

To investigate whether B lymphocytes are involved in the malignant cell clone of multiple myeloma (MM), we performed immunoglobulin gene rearrangement analysis of mononuclear cells and separated B lymphocytes, isolated from bone marrow and peripheral blood of MM patients. The B lymphocytes were separated by immunomagnetic beads, coated with an HLA class II specific antibody. Southern blot analysis with a JH probe revealed in the bone marrow of three out of seven patients identical immunoglobulin gene rearrangements in the B lymphocytes when compared to the plasma cells. Out of 10 patients, two patients with a high tumour burden were found to have monoclonal B lymphocytes in the peripheral blood. These results suggest that B lymphocytes in the bone marrow are part of the myeloma clone and that they can circulate in the peripheral blood. Although previous studies indicated that the ratio of K to lambda bearing lymphocytes in the peripheral blood can provide evidence for B cell monoclonality, we did not find a correlation between the results of K/lambda analysis and immunoglobulin gene rearrangement.     

Occurrence of thyrocyte HLA class II expression in a wide variety of thyroid diseases: relationship with lymphocytic infiltration and thyroid autoantibodies

The proteins of the major histocompatibility system (HLA in humans) play an essential role in the regulation of immune responses due to their involvement in the presentation of antigen to T lymphocytes. Thyroid follicular cells (thyrocytes) from patients with Graves' disease and Hashimoto's thyroiditis demonstrate increased expression of HLA class I and aberrantly or inappropriately express class II antigens, a phenomenon that may play an important role in the pathogenesis of these autoimmune diseases. To establish if these changes in the expression of HLA molecules are characteristic of thyroid autoimmune disease, the immunopathological features (including class I and class II antigen expression) of 100 thyroidectomy specimens from patients with nonautoimmune thyroid disease were studied by indirect immunofluorescence, and the results compared with the findings in specimens from 14 patients with Graves' disease and 12 subjects undergoing laryngectomies for carcinoma. Increased class I product expression was found in 61% of all tissues studied, with maximal occurrence in papillary carcinomas (100%) and Graves' disease (86%), but it was also detected in 50% of the glands containing nodular lesions and in 16% of the control glands. Inappropriate class II molecule expression was found in Graves' disease (71%), hyperplastic nodules (53%), multinodular glands (44%), papillary carcinomas (38%), and 16% of the control glands. In summary, an increase in inappropriate HLA class I and class II expression was very common in nonautoimmune thyroid glands, but it generally occurred in the context of lymphocytic infiltration and thyroid autoantibodies (i.e. focal thyroiditis). Multiple correlation analyses of these 4 phenomena indicated heterogeneity in the mechanism leading to the inappropriate expression of thyrocyte class II antigens in the different conditions studied.     

HLA class I antibodies in thalassemic patients

This study was undertaken to demonstrate the prevalence of HLA class I antibodies among 62 polytransfused patients. The diagnosis included beta-thalassemia major, beta-thalassemia/Hb E disease and severe Hb H disease. Their ages ranged from 1 year to 23 years with the mean age of 10.7 years. The number of packed red cell transfusions ranged from 3 to 235 with the mean of 60 episodes per patient. The standard microlymphocytotoxicity test was performed using 50 panels of lymphocytes which specifically identified the majority of HLA class I antibodies. 31/62 cases (50%) were positive for HLA class I antibodies. The detection of single or multiple antibodies depended upon the number of blood transfusions and the patients' ages. These antibodies were induced by the leukocytes present in the transfused packed red cells. Therefore, leukocyte-reduced packed red cells prepared by either additional inverted centrifrugation or leukocyte filter is suggested for the routine blood bank service.     

Leukocyte infiltration in synovial tissue from the shoulder of patients with polymyalgia rheumatica. Quantitative analysis and influence of corticosteroid treatment

Objective: To investigate the immunologic features of synovitis in patients with polymyalgia rheumatica (PMR) and to assess the modifications induced by corticosteroid. Methods. Arthroscopic biopsies of shoulder synovium were obtained from 12 patients with untreated PMR and from 7 patients with PMR that had been treated. Immunohistochemistry was performed on frozen sections utilizing a panel of monoclonal antibodies and computerized image analysis. Results. Synovitis was present in 10 of 12 (83%) untreated patients and in only 2 of 7 (29%) treated patients. The synovitis was characterized by vascular proliferation and leukocyte infiltration. Infiltrating cells consisted predominantly of macrophages and T Lymphocytes. Almost all T lymphocytes were CD45RO positive. A few neutrophils, but no B cells, natural killer cells, or γ/δ T cells were found. Intense expression of HLA class II antigens (DR moreso than DP moreso than DQ) was found in the lining layer cells as well as in macrophages and lymphocytes. DR, but not DP or DQ, was expressed by the endothelium of a few vessels. Class II antigen expression correlated with the number of macrophages and lymphocytes. Macrophage infiltration of arteriole walls was observed in 1 untreated patient without giant cell arteritis (GCA). In untreated patients, there was a positive correlation between the percentage of infiltrating T cells and the duration of disease. Steroid therapy was associated with a significant reduction in the number of blood vessels and of HLA class II expression. One treated patient who no longer had symptoms of PMR still had active synovitis: a relapse occurred 4 months after the biopsy. Conclusion. Our findings support the hypothesis that synovitis is a major cause of the musculoskeletal symptoms of PMR. There are immunologic similarities with the vascular inflammation observed in GCA. Corticosteroids act on both the vascular and cellular components of synovitis.     

Expression of CD44 and its variants on gastric epithelial cells of patients with Helicobacter pylori colonisation.

BACKGROUND--Studies have suggested that expression of the adhesion molecule CD44 may be of prognostic importance in gastric cancer. In addition, there is strong evidence that Helicobacter pylori has a role in gastric cancer. AIMS--To determine the expression of CD44 and its variants (v6, v9) and HLA class II molecules on human gastric epithelial cell and intraepithelial lymphocytes in patients with and without H pylori infection. PATIENTS--Eighteen patients (seven men and 11 women) attending for endoscopic evaluation because of upper gastrointestinal symptoms were included. An additional 10 patients (five men and five women) were analysed for CD44 variant expression). METHODS--Biopsy specimens were taken from the gastric antrum during endoscopy. Gastric epithelial cells and intraepithelial lymphocytes were examined by two colour flow cytometry and compared in patients with and without H pylori infection. RESULTS--Expression of CD44 and its variants (CD44 v9) was increased in epithelial cells but not in intraepithelial lymphocytes. Both epithelial cells and intraepithelial lymphocytes expressed higher levels of HLA class II molecules (DR and DP), possibly as a result of local cytokine production. Furthermore, results showed upregulation of CD44 on a gastric epithelial cell line (AGS) by cytokines and peripheral blood mononuclear cell supernatant. CONCLUSIONS--These data suggest that H pylori, either directly or through a local inflammatory response, is responsible for increased expression of CD44 and its variant CD44 v9. These data are of potential importance in relation to increased expression of CD44 and CD44 v9 on gastric carcinoma.     

Immunohistologic studies of differential HLA expression in patients with various intestinal diseases

Histocompatibility antigens (HLA) play an important part in immunoregulation and in cell differentiation. This study analyses the expression of HLA class I and class II antigens (DR, DP, DQ) in intestinal biopsy specimen from patients with Crohn's disease, ulcerative colitis, GvHD, radiation colitis and intestinal adenomas using the indirect immunoperoxidase technique. 92 of 94 inflamed specimen from patients with inflammatory bowel disease showed a neoexpression of HLA II (DR greater than DP greater than DQ) on their epithelial cells. The intensity of HLA-DR neoexpression was significantly dependent on an endoscopic as well as a histological index of inflammation. All 75 non-inflamed specimen except 4 from patients with Crohn's disease did not show any evidence of HLA II display on the epithelium. 4 of 18 intestinal adenomas expressed HLA II on their epithelial cells without any correlation to the type of adenoma or the degree of cell dysplasia. Furthermore all specimen from a patient with intestinal GvHD showed an aberrant epithelial HLA II expression, but not that from radiation colitis. The expression of HLA class I antigens was similar in all biopsies studied. Our results suggest, that the epithelial neoexpression of HLA class II antigens may be an important event in the pathogenesis of various bowel diseases.     

Fatal graft-versus-host disease in a patient with lymphoblastic leukemia following normal granulocyte transfusion

A woman with lymphoblastic lymphoma was treated with combination chemotherapy. She subsequently became febrile while granulocytopenic and was given unirradiated granulocyte transfusions from normal, unrelated donors. She recovered, but 12 days later noted the onset of progressive skin rash, hepatic dysfunction, diarrhea and pancytopenia and, 22 days after her last granulocyte transfusion, died of gram negative septicemia. Histologic examination of multiple tissues including the skin, liver, and intestinal tract showed changes characteristic of acute graft-versus-hose disease (GVHD). Y-chromatin analysis of the patient's peripheral blood just before death indicated the presence of male cells. HLA typing of lymphocytes and skin fibroblasts from the patient and lymphocytes from the family and granulocyte donors was also consistent with engraftment of cells from one of the male granulocyte donors. This donor most likely was homozygous for one of the patient's halotypes, perhaps facilitating engraftment of his cells and subsequent development of transfusion- induced acute GVHD. Until more precise guidelines can be established, we recommend that all cellular blood products given to patients receiving intensive chemotherapy be irradiated with 1500 rad.     

Concordant Graves' disease after bone marrow transplantation: implications for pathogenesis

The current working hypothesis on the pathogenesis of autoimmune disease focuses on the interactions between susceptibility genes and environmental stimuli. In Graves' disease it is postulated that aberrant expression of HLA class II antigens on thyroid epithelial cells permits the presentation of specific thyroid antigen to activated lymphocytes. Evidence suggests that thyrocyte HLA-DR expression is secondary to the production of cytokines by presensitized T-lymphocytes. A 20-yr-old woman and her 18-yr-old brother presented with classical findings of Graves' disease with ophthalmopathy within a year of each other. Diagnosis was confirmed by demonstration of elevated serum levels of T4 and T3, strongly positive titers of TSH binding inhibitory immunoglobulins, and histological examination after subtotal thyroidectomy. Eight years previously, acute life-threatening aplastic anemia in the brother led to therapeutic transplantation of bone marrow from his sister. After the procedure, 100% of his peripheral leucocytes were genotype 46,XX. HLA typing performed before transplantation and 2 months after thyroidectomy in the female indicated complete identity with her brother's leukocytes for class I and class II antigens. Thyroid autoantibodies at this time were weakly positive. Although the concordance of thyroid disease in these patients could be due to chance, the patients were of different sexes, the family history was negative, and neither the probands nor the first degree relatives bore the HLA-DR3/B8 antigens. We propose that the male passively acquired a clone of programmed or activated lymphocytes from his sister and that his hyperthyroidism was not primarily dependent on exposure to specific thyroid-derived antigen.