Polymorphic DQ alpha and DQ beta interactions dictate HLA class II determinants of allo-recognition.

18 transfected cell lines were generated that expressed distinct DQ molecules related to the serologically defined HLA-DQw3 specificity. These transfectants were constructed using site-directed mutagenesis to introduce nucleotide substitutions into DQ3.2 beta cDNA, followed by retrovirus-mediated gene expression of the mutagenized genes in human B cell lines with different endogenous DQ alpha chains. The capacity of particular class II dimers to stimulate alloreactive T cell clones was investigated. T cell activation was found to be dependent on both DQ alpha and DQ beta chains. In some cases, single amino acid substitutions at codons 13, 26, 45, or 57 of the DQ beta chain were sufficient to dramatically alter T cell reactivity; T cell recognition of these substitutions, however, was strongly influenced by the alpha chain polymorphisms present in the stimulatory class II dimer. Both gain and loss of major serologic and cellular specificities associated with specific DQw3+ alleles were observed with a limited array of site-directed substitutions.

The HLA-DR4 family of haplotypes consists of series of distinct DR and DS molecules.

Among DR4-associated HLA-D antigens, distinct and consistent structural variations were found for the products of two human "Ia-like" loci, DR and DS. Analysis of neuraminidase-treated immunoprecipitated DR molecules from 15 HLA-DR4-associated HLA-D homozygous B-lymphoblastoid cell lines by two dimensional polyacrylamide gel electrophoresis identified five distinct DR beta chains. In addition, gel analysis of immunoprecipitated DS molecules identified three distinct DS beta chains. Altogether, five distinct DR4 haplotypes were defined according to the observed structural diversity of the DR and DS beta chains. These gene products presumably contribute the dominant polymorphisms recognized by T cells in mixed lymphocyte reaction (MLR). Thus, these studies indicate that the serologic specificity known as HLA-DR4 is not a single haplotype, but a determinant present on products of individual loci arrayed into distinctly different haplotypes. These findings suggest that distinct products of individual loci, rather than conventional HLA specificities defined by alloimmune sera, may represent the genetic markers relevant to HLA-D/DR associated diseases.

Correlation of structure with T cell responses of the three members of the HLA-DRw52 allelic series.

A third allele at the DRB3 locus, DRw52c, represents an intermediate sequence between DRw52a and DRw52b and may have arisen by a gene conversion-like event. The recognition of cells bearing these molecules by a number of alloreactive and antigen-specific DR-restricted T cell clones was analyzed. On the basis of a theoretical model of HLA class II structure, distinct amino acid clusters have been identified as motifs controlling TCR recognition. These are located both in the cleft and in the alpha-helical edge of the MHC class II recognition platform. Motifs shared between two alleles may restrict public T cell clones.

Clinical and molecular cytogenetic characterisation of a newly recognised microdeletion syndrome involving 2p15-16.1.

BACKGROUND: During whole genome microarray-based comparative genomic hybridisation (array CGH) screening of subjects with idiopathic intellectual disability, we identified two unrelated individuals with a similar de novo interstitial microdeletion at 2p15-2p16.1. Both individuals share a similar clinical phenotype including moderate to severe intellectual disability, autism/autistic features, microcephaly, structural brain anomalies including cortical dysplasia/pachygyria, renal anomalies (multicystic kidney, hydronephrosis), digital camptodactyly, visual impairment, strabismus, neuromotor deficits, communication and attention impairments, and a distinctive pattern of craniofacial features. Dysmorphic craniofacial features include progressive microcephaly, flat occiput, widened inner canthal distance, small palpebral fissures, ptosis, long and straight eyelashes, broad and high nasal root extending to a widened, prominent nasal tip with elongated, smooth philtrum, rounding of the upper vermillion border and everted lower lips. METHODS: Clinical assessments, and cytogenetic, array CGH and fluorescence in situ hybridisation (FISH) analyses were performed. RESULTS: The microdeletions discovered in each individual measured 4.5 Mb and 5.7 Mb, spanning the chromosome 2p region from 57.2 to 61.7 Mb and from 56 to 61.7 Mb, respectively. Each deleted clone in this range demonstrated a dosage reduction from two to one copy in each proband except for clone RP11-79K21, which was present in three copies in each proband and in four copies in their respective parents (two per each chromosome 2 homologue). DISCUSSION: The common constellation of features found in the two affected subjects indicates that they have a newly recognised microdeletion syndrome involving haploinsufficiency of one or more genes deleted within at least a 4.5-Mb segment of the 2p15-16.1 region.

Mixed leukocyte reactivity and leukemia: study of identical siblings.

This report describes a search for tumor-specific transplantation antigens in man by testing four sets of identical siblings using the mixed leukocyte transformation reaction. In each case, one member of the set had acute leukemia in relapse. In no instance did the leukemic cells of the patient stimulate the cells of the normal twin, nor did cells from the normal twin stimulate cells from the leukemic patient. Possible explanations for the failure to detect a leukemia-associated antigen in these studies are discussed.

Specific HLA-DR4-associated histocompatibility molecules characterize patients with seropositive juvenile rheumatoid arthritis.

The structural and functional heterogeneity of HLA-DR4-associated specificities was investigated in patients with seropositive juvenile rheumatoid arthritis, a DR4-associated disease. Using a combination of HLA-D analysis by mixed lymphocyte culture and electrophoretic analysis of immunoprecipitated Ia molecules by two-dimensional polyacrylamide gels, we observed a surprisingly homogeneous pattern of HLA-D antigen expression. All patients expressed common structural products of the DR and DS loci, and 7/12 homozygous DR4 patients expressed a rare and subtle HLA-D heterozygous phenotype.

Effect of HLA mismatches on the outcome of hematopoietic transplants.

Hematopoietic cell transplantation from unrelated volunteer donors for the treatment of hematological malignancy can be optimized by complete and precise matching for HLA class I and II alleles between the donor and recipient. Survival is improved when the donor and recipient are matched for HLA-A, -B, -C, -DRB, -DQB1 and -DPB1 alleles. The risks of clinically severe graft-versus-host disease, graft failure and mortality are increased in the presence of multilocus mismatching. These findings demonstrate that HLA allelic differences are biologically relevant in human transplantation.

Genomics of unrelated-donor hematopoietic cell transplantation.

Unrelated-donor hematopoietic cell transplantation is a proven curative modality for hematologic malignancies. The success of unrelated-donor transplantation has been achieved through a better understanding of the immunobiology of the HLA system and through more precise and comprehensive matching of donors and recipients. The extensive polymorphism of HLA genes confers important biological implications affecting engraftment, graft-versus-host disease and overall survival. Although more-complete HLA identity of the donor and recipient is associated with optimal transplant outcome, new information suggests that not every HLA disparity is functionally relevant. Future advances in unrelated-donor transplantation must include the identification of tolerable HLA mismatches, so that more patients may benefit from this therapeutic modality. Furthermore, the role of cytokine-gene polymorphisms and minor histocompatibility genes in transplant outcome requires investigation. Delineation of the function of these markers as transplantation determinants may provide alternative means for optimizing the results of hematopoietic cell transplantation.

Autologous marrow recovery and sensitization to non-HLA antigens after HLA-identical marrow transplantation for aplastic anemia.

One hundred seventy-five patients with severe aplastic anemia were treated by high-dose cyclophosphamide and HLA-A, -B, and -D-identical sibling marrow transplants. Thirty-eight patients rejected their grafts. Four of the 38 showed autologous marrow recovery as determined by blood genetic markers. The remarkable feature of one case following autologous marrow recovery was the presence of unidirectional proliferative and cytotoxic responses of circulating host lymphocytes to marrow donor lymphocytes in mixed lymphocyte culture and cell-mediated lympholysis. Presumably these responses were the result of in vivo sensitization to those non-HLA antigens for which donor and recipient differed.

Correlation of the relative response index with marrow graft rejection in patients with aplastic anemia.

Thirty-four patients with severe aplastic anemia were treated with cyclophosphamide or total body irradiation and an infusion of marrow from a genotypically HLA-identical sibling donor. Engraftment occurred in all patients but rejection was noted in 12. Mixed leukocyte culture (MLC) tests undertaken before grafting to determine donor-recipient histocompatibility were analyzed retrospectively. The response of patient cells to sibling cells in mixed culture was compared to the response of patient cells to cells of an unrelated individual and expressed as a relative response index (RRI). Of the 12 patients who showed positive RRI to donor leukocytes in pregraft MLCs, 9 rejected their grafts, wheras of 23 patients with negative RRI only three rejected their grafts (P LESS THAN 0.005). The results suggest that the MLC test can detect individuals who are most likely to reject their HLA identical sibling graft.

Selective T-cell-receptor gene usage in allorecognition and graft-versus-host disease.

Immune recognition of foreign HLA molecules is initiated by T cell recognition mediated by alloreactive T cell receptor (TCR) molecules. We analyzed the diversity of TCR expression in the clinical setting of allorecognition in a patient with acute graft-versus-host disease following bone marrow transplantation. Nearly 200 TCR transcripts from peripheral blood lymphocytes were cloned and sequenced at two time points during GVHD. HLA genes in the transplant donor and the recipient were mismatched for a very specific HLA-DR subtype: HLA-DRB1 genes in the donor (DR4/Dw4) and the recipient (DR4/Dw14) encode HLA molecules that differ at only two amino acids, providing a very restricted target for allorecognition. We also studied TCR genes from five T cell clones derived in vitro from mixed lymphocyte cultures between Dw4-positive responder and Dw14-positive stimulator cells. Comparisons of the derived TCR sequences implicate nonrandom patterns of TCR selection both in vivo and in vitro.

Association of interstitial pneumonia and diminished in vitro lymphocyte blastogenesis in human marrow graft recipients.

The lymphocyte responses of 51 human marrow graft recipients were tested in vitro 18 to 45 days after marrow grafting by stimulation with lymphocytes from unrelated individuals or phytohemagglutinin (PHA). Fourteen of the 51 patients subsequently developed interstitial pneumonia (IP). The relative responses of the lymphocytes of patients who developed IP were significantly lower than those of individuals not developing IP (P less than 0.01 for allogeneic cells, P = 0.02 for PHA). These nonspecific in vitro tests of cell-mediated immunity are of value in identifying patients at risk of developing IP.

Alloreactive T cell responses between HLA-identical siblings. Detection of anti-minor histocompatibility T cell clones induced in vivo.

Cytotoxic T cell (CTL) clones were isolated from the peripheral blood of a patient 13 days following marrow transplantation from her HLA-identical brother. Nineteen of the clones were specifically reactive with host--but not donor--cells, but one clone was reactive with donor but not host cells. Family studies using the 19 clones showed reactivity patterns consistent with three non-HLA, minor histocompatibility antigens (minor-HA). The frequency of reactivity on a large panel of unrelated cells indicated a relatively limited degree of polymorphism. Each of the clones was restricted in its activity by a class I epitope common to HLA-B7, B27, and B40. These data demonstrate that by clonal analysis it is possible to identify in vivo antidonor and antihost alloreactive CTL clones directed against HLA determinants following marrow transplantation.

Suppressed antidonor MLC responses in renal transplant candidates conditioned with donor-specific transfusions that carry the recipient's noninherited maternal HLA haplotype.

Forty-seven patients with end-stage renal disease were entered into a donor-specific transfusion protocol consisting of three infusions of whole blood every two weeks prior to transplantation. Fourteen of the patients became sensitized following transfusion and were not transplanted. Thirty-one patients received a transplant from the DST donor and have an estimated two-year graft survival of 97%, three-year survival of 88%, and four-year survival of 69%. Cells of eleven of the 36 recipients tested in one-way MLC before and two weeks after completion of DST exhibited a significantly decreased antidonor MLC response. Deletion of CD8+ positive lymphocytes from suppressed MLCs resulted in restoration of antidonor MLC reactivity in four of six patients. An analysis of the family HLA profile in patients exhibiting a decreased donor-directed MLC response revealed a significant (P less than 0.02) association between decreased MLC reactivity following DST and the expression of noninherited maternal HLA antigens by cells of the transfusion donor. These alterations in cellular immune responses noted in some patients following DST are consistent with the appearance of specific antidonor T suppressor cells as a result of donor-specific transfusion.

Probability of finding HLA-matched unrelated marrow donors.

Bone marrow transplantation has become the treatment of choice for certain hematologic diseases. However, only 30-40% of patients who might benefit from this procedure have a suitable family donor. Consequently, many centers have begun to explore the use of unrelated volunteer donors. Initial results have demonstrated the feasibility of this approach. As a result, a national effort has begun to recruit HLA-typed volunteers in order to establish a registry of individuals who would be willing to serve as bone marrow donors. This manuscript explores the potential impact of establishing such a registry. We find that a registry of attainable size could more than double the number of marrow transplants now being performed. However, even with a registry of enormous size, it will still not be possible to identify an HLA-matched donor for some patients.

Studies of the response in mixed leukocyte culture of cells from patients with aplastic anemia to cells from HLA-identical siblings.

We have studied the mixed leukocyte culture (MLC) reactions of 64 patients with severe aplastic anemia. Their peripheral blood mononuclear cells showed an increased relative response (RR) to cells from HLA-identical siblings as compared to cells from normal HLA-identical siblings, confirming the results reported in an earlier series of 34 patients. Elevated RRs were associated with patient antidonor lymphocyte antibodies as detected by the antibody-dependent cell-mediated cytotoxicity assay, but were not associated with antidonor complement-dependent cytotoxic antibodies or with antidonor cytotoxic T lymphocytes. Among 98 patients receiving marrow grafts from HLA-identical sibling donors, those with elevated RRs before transplantation were more apt to reject the transplant than those without (P less than 0.0001). There was no elevation of the RR in 10 untransfused patients, although positive RRs were noted in 2 patients within 12 to 24 hr of their first transfusions. Five patients with identical twins were also tested, and elevated RRs were noted in three. Although blood transfusion appears to be responsible for the increased RRs observed in some aplastic patients, genetic differences between donor and recipient were not always necessary for eliciting an increased MLC response, suggesting that mechanisms other than alloimmunization are involved.

Marrow transplantation from HLA-matched unrelated donors for treatment of hematologic malignancies.

Less than 40% of the patients who could benefit from marrow transplantation have an HLA-matched relative who can serve as a donor. For this reason, several centers have explored marrow transplantation from other categories of donors. This retrospective study analyzes the results of marrow transplantation for 52 patients receiving grafts from HLA-A,B,DR,Dw-phenotypically matched, MLC-compatible, unrelated volunteer donors compared to a disease, disease-stage, and age-matched cohort of 104 patients transplanted from HLA-genotypically identical sibling donors. The patients transplanted from unrelated donors had an increased incidence of grade II-IV acute graft-versus-host disease compared to patients transplanted from related donors (79% vs. 36%, P much less than 0.001). However, the probability of relapse-free survival appears similar in the two groups (P = 0.39 over all, with estimates of 41% vs. 46% at 1 year). We conclude from this preliminary data that marrow transplantation from HLA-matched unrelated donors should be considered in most, if not all, circumstances where transplantation from an HLA-matched sibling would be indicated if such a donor were available.

Bone marrow transplantation experience for children with aplastic anemia.

From May 1971 through December 1981, 81 children (22 months to 17 years of age) received allogeneic bone marrow grafts for severe aplastic anemia. All donors were HLA-identical family members. Fifty-seven of the 81 (70%) are still alive. Twenty-three untransfused patients were conditioned with cyclophosphamide, 50 mg/kg/d, for four days, and 19 (83%) have survived from 5 to 12 years. All 58 transfused patients were conditioned with cyclophosphamide, 50 mg/kg/d, for four days, 11 received additional immunosuppression, and 19 received posttransplantation donor buffy coat cells. Thirty-eight (65%) have survived from 3 to 13 years (P = .1). In a multivariate analysis, the only factor significantly associated with increased survival among patients with sustained grafts was the absence of significant graft v host disease (P less than .0001). The factors significantly related to increased rejection were low bone marrow cell dose (P less than .05) and positive relative response in mixed leukocyte culture (P less than .0001), but the addition of buffy coat cells did not significantly influence graft rejection. The development of grades II to IV acute graft v host disease was associated with random donor platelet refractoriness (P less than .05) and donor/recipient sex differences (P less than .05). Patients at highest risk for chronic graft v host disease were those patients who developed significant acute graft v host disease (P less than .01) and who received buffy coat infusions (P less than .025). All patients who were untransfused had a negative relative response and were not refractory to random donor platelets.

Two homozygous typing cells defining a subgroup of HLA-Dw6.

Homozygous typing cells (HTC) and responder cells from a panel of randomly selected unrelated caucasians were used in a study of the HLA-Dw6 antigen complex. Using HTC characterized by the Eighth International Histocompatibility Workshop, the Dw6 specificity was shown to be a broadly defined, heterogeneous cluster that could be subdivided. An HTC from our laboratory, 8W146, and a second locally identified cell, EMJ, were used to define one clearly distinguishable subcluster of Dw6, provisionally termed "6.1." HTC 8W146 and EMJ were mutually nonreactive in mixed leukocyte culture and showed strong association (r = 0.85) when used as stimulators against the caucasian cell panel. The calculated gene frequency of the 8W146/EMJ determinant in this population was 0.024. In an informative family, the 6.1 specificity could be shown to segregate independently of other Dw6 subgroups. DR typing of 8W146 and EMJ showed both to be positive for MT-1 and MT-2 but negative for DRw "3 + 6."

Variants of HLA-DRw52 defined by T lymphocyte clones.

Polymorphism within the gene encoding the DRw52 allospecificity was studied with DRw52-specific proliferative T lymphocyte clones. Three clones, C6, E3 and ZUK16, were generated by intra-DRw52 priming in mixed lymphocyte culture and tested against an HLA-D homozygous reference cell panel. The reactivity of each clone could be specifically inhibited by anti-DR, but not anti-DQ or anti-DP, monoclonal antibodies. Clone C6 identified a DRw52 variant termed 52a that was predominantly expressed by HLA-B8,DR3+ and DRw13,Dw18+ cells. Clone E3 identified a variant termed 52b which was predominantly expressed by HLA-B18,DR3+,DRw11,Dw5+ and DRw14,Dw9+ cells. Clone ZUK16 identified a variant termed 52c which was predominantly expressed by DRw13,Dw19+ cells. The DRw52a, 52b and 52c variants correspond to the Dw24, Dw25 and Dw26 alleles defined by the WHO HLA 1987 Nomenclature Committee. Together, clones E3 and ZUK16 appeared to identify a fourth DRw52 variant termed 52d which was expressed by two cells, one DR3, Dw"3.3"+ and one DRw14,Dw"9.2"+. A fifth Drw52 variant termed 52e, expressed by a DRw13,Dw"OMW"+ cell, was suggested by the absence of reactivity with any of the three T cell clones. These data thus demonstrate the existence of three well-defined allelic variants of DRw52 and indicate that there are at least two additional variants. The recognition of these polymorphisms by alloreactive T cells provides one measure of their functional significance.