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.

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.

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.

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.

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.

DQw3 variants defined by cloned alloreactive T cells.

The polymorphism of HLA class II molecules expressing the serologically defined alloantigen DQw3 was studied using cloned proliferative T lymphocytes. Two clones, IG9 and IC3, were selectively primed against DQw3-associated determinants and tested against a panel of 92 HLA-D homozygous cells. Both clones were specific for DQw3, but each showed a distinct response pattern. Clone IG9 recognized a DQw3-associated determinant expressed on a subset of DR4 and DR5 haplotypes and on all DRw6, 7, w8, and w9 haplotypes tested. In contrast, clone IC3 recognized a distinct DQw3-associated determinant expressed only on a subset of DR4 haplotypes. In monoclonal antibody inhibition experiments, anti-DQ, but not anti-DR or anti-DP antibodies, blocked reactivity of both clones IG9 and IC3, further demonstrating that the determinants defined by these clones are associated with DQ molecules. In DNA hybridization studies using a DQ beta probe, a correlation was observed between restriction site polymorphisms in the DQ beta gene, designated DQw"3.1" and "3.2," and the expression of the T-cell-defined IG9 and IC3 determinants. It is, thus, possible to demonstrate by cloned T-cell reactivity functionally relevant recognition sites on DQw3+ molecules that are associated with structural polymorphisms defined by molecular and genomic analysis.

Immune responses in an untransfused patient with aplastic anemia: analysis of cytolytic and proliferative T cell clones.

Unexpected unidirectional reactivity was noted in MLC by the cells of an untransfused patient with aplastic anemia against cells from her genotypically HLA identical brother. To analyze this reactivity, lymphocytes from the patient were primed in vitro for six days with irradiated lymphocytes from the HLA identical brother and then cloned by limiting dilution in the presence of interleukin-2. Following a period of clonal expansion, the patient's cells were tested for specific proliferative (PLT) and cytolytic (CTL) activity against cells of the brother. Thirty-six clones demonstrated proliferative activity, 30 clones demonstrated cytolytic activity, and 114 clones showed neither. No clone demonstrated both cytotoxic and proliferative activity. Several patterns of specificity were seen for the cytolytic T cell (CTL) clones, including both allo- and autoreactivity. Two distinct patterns of specificity were noted for the proliferative clones: one reactive to cells from DR3-positive males; the other reactive only to cells from certain DR2-positive males and females. The DR3-restricted clones are presumably directed towards the H-Y minor histocompatibility antigen while the DR2-restricted clones are directed toward an undefined minor histocompatibility antigen. It is thus possible to isolate both alloreactive and autoreactive T cells from the peripheral blood of some untransfused patients with aplastic anemia.

Definition of LD "4 X 7": a unique HLA-D specificity defined by two homozygous typing cells.

Two homozygous typing cells (HTC) from the Eighth International Histocompatibility Workshop were used to define a unique HLA-D specificity, designated LD "4 X 7". Typing cell 8W316 (Seattle) was obtained from a donor of Japanese descent; cell 8W324 (Leiden) was obtained from a European Caucasian donor. The HLA-D specificities defined by these two HTC showed a significant correlation (R = 0.65) in unselected panel studies and clear segregation as a single determinant within families. LD "4 X 7" was found in low frequency in Caucasians (1.0%) but with detected with a frequency of 24% in Japanese. The cells of the donors of HTC 8W316 and 8W324 express DRw9, and the LD "4 X 7" antigen fills an HLA-D locus "blank" on DRw9-positive haplotypes. The frequency of LD "4 X 7" noted in this study corresponds to the frequency of DRw9 reported for Japanese and Caucasian ethnic groups, a further indication that LD "4 X 7" and DRw9 are associated.

Change in functional phenotype of cloned human alloreactive cytolytic T cells.

Alloreactive T cell clones primed in vivo were tested for the expression of T cell differentiation antigens CD2, CD3, CD4, and CD8. Each of 29 different clones were found to express CD2 and CD3, but were variable in their expression of CD4 (7 positive clones) and CD8 (15 positive clones). Six clones were positive for both CD4 and CD8. One of the 29 clones expressed neither CD4 or CD8. Over a period of 12-18 weeks of culture, these clones began to lose their alloreactivity but acquired NK-like activity. By changing the concentration of TCGF, the "allo" and "NK-like" lytic activities could be modulated. After 18 weeks of culture, these clones lost their alloreactive specificity, but not their NK activity. The expression of surface markers was unchanged. CD2 and CD3 molecules were determined to play a role in both the alloreactive and NK activity of these clones.

T-cell receptor V beta selectivity in T-cell clones alloreactive to HLA-Dw14.

The HLA-DR4 subtypes Dw14 and Dw4 are T-cell-defined allospecificities encoded by the DRB1*0404 and DRB1*0401 genes, respectively. Although these allelic subtypes differ in only two amino acids, allorecognition between Dw14 and Dw4-positive individuals is brisk. This provides an opportunity to analyze T-cell receptor (TCR) usage in a very limited and specifically targeted case, namely the Dw4 anti-Dw14 allogeneic T-cell response. The variable (V), diversity (D), and joining (J) region sequences of the TCR beta chain from two different Dw14-specific alloreactive T-cell clones derived from a Dw4 donor were examined. Clone EMO25 recognized the Dw14.1, Dw14.2, and Dw15 subtypes, which share a DRB1 polymorphism at codon 71 on a DR4 background, while clone EMO36 reacted with only the Dw14.1 subtype associated with polymorphisms at codons 71 and 86. TCR beta cDNA from each clone was amplified using an anchored polymerase chain reaction (PCR) and subsequently expanded with V beta- and C beta-specific primers for asymmetric PCR and direct DNA sequencing. Both clones were found to express the same TCR V beta 8.2 gene segment; however, they have several different residues within the V beta-D beta-J beta junctional regions. V beta 8 usage was also enriched in polyclonal cells obtained from mixed lymphocyte cultures performed between the Dw4 and Dw14 responder-stimulator combination from which EMO25 and EMO36 were derived.

HLA matching in hematopoietic cell transplantation.

Progress in hematopoietic cell transplantation has been greatly facilitated by our increasing knowledge of the HLA system, as well as by improved therapies for achieving sustained engraftment, preventing graft-versus-host disease, and protecting the patient from infection. Disparity for HLA genes can cause graft rejection and graft-versus-host disease and decrease survival in patients receiving grafts from both related and unrelated donors. The presence of patient alloantibodies against donor antigens demonstrated by a positive crossmatch is a strong risk factor for graft rejection. The availability of matched donors for patients lacking a genotypically HLA-matched sibling has been greatly improved by the establishment of international registries of HLA-typed volunteer donors. The development of accurate and reproducible high-resolution DNA-based typing methods has significantly improved the prospects for identifying unrelated donors who are well matched with the patient for HLA. The use of these methods to optimize donor selection will improve both donor identification and the success of unrelated donor transplants.

Marrow transplantation from donors other than HLA identical siblings.

As of 31 December 1979, 39 patients in Seattle have received marrow grafts from donors other than HLA genotypically identical siblings. Sixteen transplants were between siblings, 21 from a parent to a child, one from a paternal uncle, and one from an unrelated donor. Ten patients had aplastic anemia and 29 had a hematological malignancy. As of 1 February 1980, only one of the ten patients transplanted for aplastic anemia is currently alive (greater than 1048 days) with a normal marrow and without graft-versus-host disease. This surviving patient was untransfused and received marrow from an HLA phenotypically identical mother. There were five episodes of graft rejection among the ten aplastic patients. Among the 29 patients transplanted for hematological malignancy, 12 (42%) are surviving from greater than 64 to greater than 995 days. Twelve of 29 patients were transplanted while in remission and eight (75%) are alive from greater than 148 to greater than 790 days. The two most frequent causes of death were relapse of leukemia and interstitial pneumonia. Only two patients died from complications clearly related to graft-versus-host disease. Five of the surviving patients were phenotypically identical with their donor for HLA, while seven were incompatible for some HLA determinants. One patient--donor pair was incompatible for HLA-D and DR as a result of HLA-B/D recombination, and six pairs were incompatible for HLA-A and/or B.

Alloreactive T-cell clones identify multiple HLA-DQw3 variants.

HLA-DQw3 is a broadly defined alloantigen that has been subdivided by serological, biochemical, and molecular methods into three distinct specificities: DQw7, DQw8, and DQw9. In order to characterize functionally relevant structural polymorphisms within this family of alloantigens, we generated a series of DQw3-reactive T-cell clones that together recognize six different variants of DQw3. T-cell clones IG11 and IG9 were found to recognize three distinct functional variants associated with a majority of DQw3+ cells, while clones 21J, IE6, 64B, and IC3 recognized four more narrowly distributed functional variants associated with unique DQw7, DQw8, and DQw9 subsets. Comparison of known DQB gene sequences suggested candidate recognition sites for clones IG11 and 64B in the region of amino acid residues 66 to 71 and residue 57 of the DQ beta chain. In contrast, no unique DQB or DQA sequences were found that individually corresponded to the reactivity patterns of clones 21J, IE6, IG9, or IC3, suggesting that an interaction between DQ alpha and DQ beta chains determines allo-recognition. These data are consistent with the hypothesis that T cells recognize specific alloepitopes on HLA class II molecules, either as distinct structural elements that trigger an alloresponse or, more indirectly, as contact elements that influence alloreactivity by governing the binding of foreign peptide. The results illustrate the diversity of possible T cell responses directed toward HLA-DQ molecules and suggest that T cell recognition of the DQ heterodimer alone, or a peptide antigen bound to the DQ heterodimer, can be affected either by the individual DQ alpha and beta chains, or by a more complex interaction between the two.

Definition of DW8.2 by primary and secondary mixed lymphocyte cultures.

Using HLA-DW8 homozygous typing cells (HTC) of different ethnic origin it is possible to identify three subgroups of the DW8/DRW8 product (Mickelson et al., 1983). To further characterize the DW8.2 subgroup defined by HTCs of Amerindian origin we have now generated bulk PLTs within members of one extended Amerindian family and within selected HTCs of Caucasian, Oriental, and Amerindian origin. A panel of 61 DRW8 positive and negative donors of the three ethnic groups was used to test 15 different PLTs. Our results demonstrate that it is possible to generate DW8.1, 8.2, or 8.3 sensitized lymphocytes which distinguish in secondary cultures between each of the three subgroups of the DW8/DRW8 products. Of 40 DRW8 cells tested, 100% Caucasians typed as DW8.1, 100% Amerindians were 8.2; 75% Orientals were DW8.3; 8.3% were DW8.2, and 16.6% could not be classified within any of these subgroups. DRW8 individuals of mixed ethnic origin typed as either DW8.1 or DW8.2 and one DRW8 homozygous donor behaved as heterozygous 8.1/8.2. These results confirm the subdivision of the DW8/DRW8 product and explain the poor correlation and unexpected responses reported in MLC with DW8 HTCs and DRW8 donors of different ethnic origin.

T-cell clones identify three distinct epitopes associated with HLA-Dw14.

Alloreactive T-cell clones were used to study allodeterminants associated with the HLA-DR1, -DR4, and -DRw14 allelic families. Three clones derived by priming against the DR4,Dw14 alloantigen were tested against a panel of HLA-D homozygous B-cell lines and homozygous and heterozygous peripheral blood lymphocytes. Each clone was blocked by monoclonal antibodies specific for HLA-DR, but not HLA-DQ or -DP, molecules, and each showed a unique pattern of allorecognition when tested against the cell panel. Clone 14B appeared to recognize a specific sequence, termed L67-A74, comprised of amino acids in the third hypervariable region of the alpha-helix of the DR beta 1 molecule, and expressed on certain DR1-, DR4-, and DRw14-positive cells. Clone EMO25 recognized the same L67-A74 sequence, but only when expressed on DR4-positive cells, suggesting a role for residues in the first and second hypervariable regions of DR4-positive DR beta 1 molecules in T-cell recognition. Clone EM036 also recognized the L67-A74 sequence, but only when expressed on DR4,Dw14.1-positive cells, implicating residues at positions 57 and 86 of the alpha-helix in T-cell recognition. These results demonstrate the range of specific T-cell responses that are possible against alloepitopes expressed by a single class II allele (Dw14), and are an indication of the diverse regions of the class II molecule that can contribute to allorecognition sites.