HLA-A2 reactive antibodies in a patient who types as HLA-A2: The importance of high resolution typing and epitope-based antibody analysis

This report describes a case of a highly sensitized patient who had serum antibodies reacting with HLA-A2 but whose phenotype included HLA-A2. The determination of HLA mismatch acceptability at the antigen level was problematic, but high-resolution HLA typing information and epitope-based antibody specificity analysis based on the nonself-self paradigm of HLA epitope immunogenicity have provided a solution. This case supports the concept that HLA typing at the allele level offers a better approach to identifying suitable donors for sensitized patients.

Should HLA mismatch acceptability for sensitized transplant candidates be determined at the high-resolution rather than the antigen level?

Defining HLA mismatch acceptability of organ transplant donors for sensitized recipients has traditionally been based on serologically defined HLA antigens. Now, however, it is well accepted that HLA antibodies specifically recognize a wide range of epitopes present on HLA antigens and that molecularly defined high resolution alleles corresponding to the same low resolution antigen can possess different epitope repertoires. Hence, determination of HLA compatibility at the allele level represents a more accurate approach to identify suitable donors for sensitized patients. This approach would offer opportunities for increased transplant rates and improved long term graft survivals.

First report on the antibody verification of HLA-ABC epitopes recorded in the website-based HLA Epitope Registry

The International Registry of Antibody-Defined HLA Epitopes ( http://www.epregistry.com.br) has been recently established as a tool to understand humoral responses to human leukocyte antigen (HLA) mismatches. These epitopes are defined structurally by three-dimensional molecular modeling and amino acid sequence differences between HLA antigens. So-called eplets represent essential components of HLA epitopes and they are defined by polymorphic residues. A major goal is to identify HLA epitopes that have been verified experimentally with informative antibodies. Our analysis has also included data in many publications. As of 1 November 2013, 95 HLA-ABC antibody-verified epitopes have been recorded, 62 correspond to eplets and 33 are defined by eplets paired with other residue configurations. The Registry is still a work-in-progress and will become a useful resource for HLA professionals interested in histocompatibility testing at the epitope level and investigating antibody responses to HLA mismatches in transplant patients.

16th IHIW: a website for antibody-defined HLA epitope Registry

The concept that HLA antibodies are specific for epitopes rather than HLA antigens is important not only for the determination of mismatch acceptability for sensitized patients but also for a better understanding of the antibody response to an HLA mismatch. Numerous publications describe epitope-specific antibodies, but there is no standardized information about the repertoire of clinically relevant HLA epitopes. Under auspices of the 16th IHIW, we have developed a website-based registry of antibody-verified HLA epitopes. Epitope notations are based on HLA molecular modelling of amino acid residues in polymorphic sequence positions. Informative epitope-specific antibodies had been induced by a transplant, transfusion or pregnancy and were monoclonal antibodies or eluates of sera absorbed with single HLA alleles. Antibody reactivity was determined in binding assays with single-allele panels. Antibody producer/immunizer HLA types enhanced the characterization of specific epitopes. The Registry also includes epitopes described in original research publications. Based on the extent of antibody reactivity information, we assigned epitope status as confirmed (well documented) or provisional (more data are needed). At present, the Registry has 69 HLA-ABC, 53 DRB1/3/4/5, 17 DQ, 8 DP and 22 MICA antibody-verified epitopes and will be updated on a quarterly basis. Laboratories worldwide continue to submit data about previously unreported antibody-specific epitopes. For each epitope, the website shows its amino acid composition and HLA alleles that share the epitope. Links show antibody reactivity patterns, sensitization information and references. Other links show molecular modelling of corresponding structural epitopes and polymorphic residue information for epitope-carrying alleles. The website will also have a link to epitope frequency information in different populations. Search functions will list mismatched epitopes on mismatched alleles for selected HLA types. The HLA Epitope Registry will become a valuable resource for researchers interested in HLA compatibility at the epitope level and investigating antibody responses to HLA mismatches.

The antibody response to an HLA mismatch: a model for nonself-self discrimination in relation to HLA epitope immunogenicity

Antibodies to HLA mismatches are specific for epitopes rather than antigens. HLAMatchmaker considers each HLA antigen as a string of eplets that represent key elements of epitopes. Certain antibodies are specific for single eplets, but recent studies have demonstrated that epitopes defined by eplet pairs always involve one nonself-eplet and a self-eplet shared between the immunizing antigen and the antibody producer. This suggests an autoreactive component of the alloantibody response to an HLA mismatch and this report expands this concept. During B-cell development, V(H) and V(L) gene rearrangements produce a diversity of Ig receptors that can recognize epitopes on autologous proteins. It is hypothesized that B cells carry low-affinity receptors for self-HLA antigens. Their interactions with self-HLA proteins will not lead to B-cell activation or antibody production. In contrast, exposure to HLA mismatches induces often strong alloantibody responses. The activation of self-HLA-specific B cell by a nonself-eplet may require that the remainder of the structural epitope of the immunizing antigen has considerable structural similarity with one of the antibody producer's alleles. This hypothesis has been tested in molecular modelling studies with six epitopes defined by human monoclonal antibodies. In each case, one allele of the antibody producer had no or few differences with the immunizing allele in antibody-accessible positions defined by a 15 Ångstrom radius of the mismatched eplet. The other alleles of the antibody producer showed significantly greater numbers of residue differences with the immunizer (5.8 ± 2.0 versus 1.0 ± 0.6, P < 0.0001). These data support the concept that HLA antibodies originate from B cells with self-HLA immunoglobulin receptors that recognize mismatched eplets as nonself entities on immunizing antigens. The nonself-self paradigm provides a new insight of HLA epitope immunogenicity and may explain why sensitized patients have antibodies to a restricted number of mismatched epitopes.

Antibody-reactive epitope determination with HLAMatchmaker and its clinical applications

Antibodies against allogeneic human leukocyte antigen (HLA) molecules are important impediments to the success of different clinical procedures including transplantation and platelet transfusion. In these settings, characterization of the repertoire of immunogenic epitopes is important for permissible mismatch determination and the identification of acceptable mismatches for sensitized patients. HLAMatchmaker is a computer algorithm that considers small configurations of polymorphic residues referred to as eplets as essential components of HLA epitopes. This review critically elaborates the concepts underlying the HLAMatchmaker and describes the usefulness of HLAMatchmaker in the clinical setting. Recent developments have increased our understanding of structural basis of HLA antigenicity (i.e. reactivity with specific antibody) and immunogenicity (i.e. its ability to induce an antibody response).

Correlations between Terasaki's HLA class II epitopes and HLAMatchmaker-defined eplets on HLA-DR and -DQ antigens

Human leukocyte antigen (HLA) class II-specific antibodies increase the risk of transplant failure, and their characterization must consider epitopes rather than antigens. There are two strategies to determine HLA epitope structure. Terasaki's group has analyzed antibody reactivity patterns with single antigen panels with a computer program based on shared amino acid residues of reactive alleles. HLAMatchmaker is a theoretical algorithm that predicts HLA epitopes on the HLA molecular surface from stereochemical modeling of epitope-paratope interfaces of antigen-antibody complexes. Our epitope repertoire is based on so-called 'eplets' representing 3-A patches of at least one polymorphic residue on the molecular surface. This report describes how 49 of 53 Terasaki's HLA-DR epitopes correspond to HLAMatchmaker-defined eplets. Most of them are equivalent to single eplets (n = 33) or two or more possible eplets (n = 10), but six had corresponding eplet pairs. There were 10 cases whereby eplets have permissible residue combinations, and in 5 cases, we found that eplet specificity might be influenced by nearby hidden residues. We could assign corresponding eplets to 17 of 18 Terasaki's HLA-DQ epitopes. This study demonstrates how the HLAMatchmaker interpretation of amino acid residues shared between antibody-reactive antigens can increase our understanding of the structural basis of HLA epitopes.

Correlations between Terasaki's HLA class I epitopes and HLAMatchmaker-defined eplets on HLA-A, -B and -C antigens

Although the determination of human leukocyte antigen (HLA) antibody specificity has traditionally been directed toward HLA antigens, there is now increasing attention to structurally defined HLA epitopes. An understanding of the HLA epitope repertoire is important to acceptable mismatching for sensitized patients and to a new epitope-based matching algorithm aimed to reduce antibody-mediated rejection. There are two strategies to determine the HLA epitope repertoire. Terasaki's group has used an empirical method to analyze the reactivity of single allele Luminex panels with mouse monoclonal antibodies (mAbs) and absorbed/eluted alloantibodies with a computer program based on shared residues in the amino acid sequences of reactive alleles. HLAMatchmaker is a theoretical algorithm that predicts HLA epitopes on the HLA molecular surface from stereochemical modeling of epitope-paratope interfaces of antigen-antibody complexes. Our epitope repertoire is based on so-called 'eplets' representing 3-A patches of at least one polymorphic residue on the molecular surface. A comparative analysis has shown that 81/103 Terasaki's HLA class I epitopes are equivalent to individual eplets (n = 50) or pairs of eplets (n = 31) separated far enough to serve as potential contact sites for two complementarity-determining regions of antibody. An additional 12 Terasaki's epitopes (TerEps) correspond to eplets with permissible residue combinations that do not seem to affect epitope specificity. We could not identify corresponding eplets for the remaining 10 TerEps, including 8 that might be considered xeno-epitopes defined by mouse mAbs. Conversely, HLAMatchmaker has 38 additional eplets in well-exposed surface positions that do not have equivalent TerEps, and for many of them, we have found specific antibodies. These findings strengthen the concept that eplets are essential basic units of HLA epitopes and that they provide a better understanding of HLA immunogenicity (i.e. ability to induce an antibody response) and antigenicity (i.e. reactivity with specific antibody).

14th International HLA and Immunogenetics Workshop: report on the structural basis of HLA compatibility

Under auspices of the 14th International Human Leukocyte Antigen (HLA) and Immunogenetics Workshop, multilaboratory collaborative studies were organized addressing the following projects: (1) identification of structurally defined class I and class II HLA epitopes by human monoclonal antibodies, (2) assessment of the relative immunogenicity of structurally defined donor HLA mismatches in kidney transplantation, and (3) evaluation of the usefulness of structurally based HLA matching in platelet transfusion support of alloimmunized thrombocytopenic patients. This progress report describes a preliminary HLAMatchmaker-based data analysis in each project. The findings support the clinical usefulness of structural HLA matching.

Evidence for heat shock protein immunity in a rat cardiac allograft model of chronic rejection

BACKGROUND

The stress response to injury concept has been proposed as a mechanism of chronic rejection. This hypothesis has been tested with a rat cardiac allograft model in recipients pretreated with donor bone marrow (BM) cells. Chronic rejection is manifested in this BM group by obliterative arteriopathy and the epicardium and endocardium contains lymphocytic infiltrates resembling Quilty lesions. Pretreatment with a liver allograft (the orthotopic liver transplant [OLTx] group) is associated with an absence of chronic rejection in the transplanted heart.

METHODS AND RESULTS

. Stress responses in the allograft were assessed by determining heat shock protein (hsp) expression by immunohistology of graft tissues and immunoblot analysis of stromal tissue lysates with monoclonal antibodies (mAb) to mammalian hsp60, the inducible hsp72, the constitutively expressed hsc73, and the grp78 C-terminal sequence KSEKDEL (grp78seq). Immunostaining showed clusters of grp78seq-positive cells in the inflammatory infiltrates of obliterated blood vessels and Quilty lesions in the BM group of cardiac allografts. Such grp78seq-positive cells were not seen in the OLTx group of heart allografts nor in syngrafts. Neither group showed significantly different graft myocyte staining of grp78 or hsp72, whereas hsp60 and hsc73 showed higher expression in the BM group and, to a lesser extent, the OLTx group. The increased expression of hsc73 was seen especially in the obliterated arteries and in myocytes nearby cellular infiltrates. Immunoblot analysis of graft stromal tissue lysates showed additional bands with mAb to hsp60 and hsc73 for the OLTx and especially the BM group. No significant bands were seen for hsp72 and grp78. Lymphocytes isolated from chronically rejecting allografts reacted with irradiated autologous spleen cells in the presence of mycobacterial hsp65 and interleukin-2. Culturing of graft-infiltrating cells with mycobacterial hsp71 and interleukin-2 yielded lymphocyte clones without alloreactivity, but with strong proliferative responsiveness to self-antigen-presenting cells and, only in the presence of mycobacterial hsp71 or murine grp78. This T-cell reactivity seemed to require intact hsp molecules because treatment of hsp71 with proteolytic enzymes, polymyxin, or ATP abrogated this induction of the stimulatory effect of self-antigen-presenting cells. These T cells are similar to the hsp-dependent, autoreactive lymphocytes cloned from acutely rejecting rat allografts.

CONCLUSIONS

These findings support the concept that the pathogenesis of chronic rejection involves a stress response and the participation of graft-infiltrating autoreactive T cells that operate under hsp-dependent mechanisms.

Role of HLA antigens in liver transplantation with special reference to cellular immune reactions

In previous statistical analyses we have demonstrated the importance of the dualistic effect of HLA on liver transplant survival: HLA compatibility decreases cellular rejection but also increases other immunologically mediated, HLA-restricted mechanisms of allograft injury. More recently these results have been confirmed by other researchers, and several studies have shown higher recurrence rates of infectious diseases such as hepatitis B and C and CMV hepatitis for HLA-compatible liver transplants. Although current practice does not consider HLA in liver transplantation, cellular in vitro studies show a significant role of HLA antigens in clinically relevant phenomena. While increasing the amount of infection-related immune damage, HLA compatibility also decreases the alloproliferative response of the recipient to the donor tissue. Further studies must examine whether non-HLA antigens such as tissue-specific antigens and heat-shock-proteins participate in this process, and how target cells can present different peptides such as soluble HLA antigens or viral proteins to the recipient.

Determination of HLA-A,B residue mismatch acceptability for kidneys transplanted into highly sensitized patients: a report of a collaborative study conducted during the 12th International Histocompatibility Workshop

BACKGROUND

During the 12th International Histocompatibility Workshop, a collaborative study between 35 laboratories was conducted on a group of highly allosensitized patients who had received a kidney transplant from 1981 to 1995. The major goal of the study was to assess how serum screening against a large cell panel could determine donor HLA mismatch acceptability in relation to graft outcome.

METHODS

Twenty laboratories participated in an extensive screening of 92 high panel-reactive antibody (PRA) sera from patients at 29 transplant centers worldwide; each patient had received a kidney allograft from an HLA-A,B mismatched unrelated donor. Screening was done by complement-dependent lymphocytotoxicity and antihuman globulin augmentation techniques using a common protocol and shared standardized reagents. After an extensive quality-control assessment, we selected data from 14 participants who had screened the sera against a combined panel of 535 HLA-typed cells.

RESULTS

With the 2x2 table-based Multiscreen computer program, we could readily determine for virtually every patient the significant correlations between serum reactivity and the presence of panel cell markers, including private and public HLA-A,B epitopes and amino acid residues assigned from published sequencing data. Donor mismatch acceptability was assessed at the amino acid residue level. In the complement-dependent lymphocytotoxicity (n=49; PRA=84.1+/-12.1%) and antihuman globulin (n=60; PRA=92.5+/-5.8%) groups, the 3-month graft survivals were 28% and 30% lower for unacceptable residue mismatches.

CONCLUSIONS

These studies underscore the importance of a comprehensive serum screening analysis in the selection of appropriately mismatched donors for highly sensitized transplant patients.

Identification of two types of autoreactive T lymphocyte clones cultured from cardiac allograft-infiltrating cells incubated with recombinant mycobacterial heat shock protein 71

Recent studies in several laboratories have advanced the concept that during cellular rejection, the allograft undergoes a stress response which regulates the expression of stress proteins (or heat shock proteins, hsp) and triggers the recruitment and activation of hsp-reactive lymphocytes. In a rat model of heterotopic heart transplants we have found that allograft-infiltrating lymphocytes respond to recombinant mycobacterial hsp and irradiated syngeneic spleen cells as a source of self-APC (antigen-presenting cells). This report describes T cell clones generated by culturing ACI into Lewis rat cardiac allograft-derived lymphocytes with mycobacterial hsp71, syngeneic spleen cells and IL-2 (interleukin-2). Two groups of self-APC-reactive T cell clones have been distinguished, all of them are CD3+, CD4+, CD8-. One group is referred to as hsp71-dependent, autoreactive T cells because these clones respond to self-APC but only in the presence of hsp71. No reactivity is seen with mycobacterial hsp65 or when hsp71 is tested with allo-PC from ACI donors or third-party APC from Brown Norway (BN) rats. Treatment of hsp71 with trypsin, polymyxin B or ATP-agarose chromatography abrogates the hsp71 effect thus indicating that structurally intact hsp71 must interact with self-APC which then activate hsp71-dependent, autoreactive T cells. The second group of clones reacts to self-APC and while their response does not require the presence of hsp71, their proliferation is often augmented by hsp71 but not by hsp65. These hsp71-independent, autoreactive clones do not respond to allo-APC from ACI donors or third-party APC from BN rats. Polymyxin or trypsin treatment had no significant effect on their proliferative responses. The data with the anti-TCR-alpha beta monoclonal antibody R73 offer additional evidence for two functionally different types of self-APC reactive CD4 cells infiltrating the allograft. R73 inhibits the proliferation of self-APC induced responses of hsp-71-independent clones as well as the allo-APC induced responses of alloreactive T cell clones. In contrast, this antibody augments the responses of hsp71-dependent T cells. Moreover, these clones can also proliferate in response to self-APC when hsp71 is substituted by R73. The hsp71-dependency of self-APC reactive T cell reactivity represents a previously unrecognized mechanism of cellular immunity to allografts. This mechanism might be related to the peptide binding properties of hsp71 and the ability of stress proteins to function as molecular chaperones in antigen processing.

Interleukin-2 and interleukin-12 mediate distinct effector mechanisms of liver allograft rejection

Interleukin-2 (IL-2), interleukin-12 (IL-12) or interleukin-4 (IL-4) were administered postoperatively to otherwise spontaneously accepting mouse liver allograft recipients (C57BL/10-->C3H) to test whether TH1 cytokines are critical mediators of rejection in this model. The induction of rejection at days 5 to 7 by exogenously administered IL-2 and IL-12, but not IL-4, suggests that mouse liver allograft rejection can be induced by TH1 cytokines; however, there appeared to be differences in the mechanism by which these cytokines induce liver rejection. IL-2 administration was accompanied by an increased intragraft infiltration of CD4+ and CD8+ cells and an up-regulation of natural killer (NK), lymphokine-activated killer (LAK), allospecific cytotoxic killer (CTL) activity and perforin mRNA when compared with media-treated controls. In contrast, exogenous IL-12 treatment was associated with a suppression of CTL, NK, and LAK activity compared with controls but an enhanced infiltration of F4/80+ macrophages as determined by immunohistochemistry. Determination of cytokine mRNA profiles by semi-quantitative reverse transcription polymerase chain reaction showed the up-regulation of interferon (IFN)-gamma, IL-4, IL-6, and IL-10 mRNA with IL-2 treatment when compared with media-treated controls. Interestingly, IL-2 mRNA was down-regulated in these animals, suggesting a negative feedback mechanism in IL-2 regulation. IL-12 treatment resulted in the up-regulation of IFN-gamma, IL-6, and IL-10 mRNA, but not IL-2 or IL-4 mRNA. Higher complement-directed cytotoxic antibody titers were seen in IL-12-treated recipients compared with controls, whereas IL-2 treatment showed no apparent differences in antibody titers compared with media treatment. These in vivo observations were mimicked in a mixed leukocyte reaction by supplementing the reaction with IL-2, IL-12, or media. These results suggest that rejection of mouse liver allografts may involve more than one distinct cellular immunological effector mechanism. One is mediated by IL-2 and appears to favor alloreactive CTL, whereas the other pathway is mediated by IL-12/IFN-gamma and involves macrophages and cytotoxic antibodies largely resembling a delayed-type hypersensitivity reaction.

Analysis of chronic rejection and obliterative arteriopathy. Possible contributions of donor antigen-presenting cells and lymphatic disruption

Sequential analysis of changes that lead to chronic rejection was undertaken in an animal model of chronic rejection and obliterative arteriopathy. Brown Norway rats are pretreated with a Lewis bone marrow infusion or a Lewis orthotopic liver allograft and a short course of immunosuppression. They are challenged 100 days later with a Lewis heterotopic heart graft without immunosuppression. The heart grafts in both groups undergo a transient acute rejection, but all rats are operationally tolerant; the heart grafts are accepted and remain beating for more than 100 days. Early arterial remodeling, marked by arterial bromodeoxyuridine incorporation, occurred in both groups between 5 and 30 days during the transient acute rejection. It coincided with the presence of interstitial (but not arterial intimal) inflammation and lymphatic disruption and resulted in mild intimal thickening. Significant arterial narrowing occurred only in the bone-marrow-pretreated rats between 60 and 100 days. It was associated with T lymphocyte and macrophage inflammation of the heart graft that accumulated in the endocardium and arterial intima and adventitia near draining lymphatics. There also was loss of passenger leukocytes from the heart graft, up-regulation of cytokine mRNA and major histocompatibility class II on the endothelium, and focal disruption of lymphatics. In contrast, long-surviving heart grafts from the Lewis orthotopic liver allograft pretreated group are near normal and freedom from chronic rejection in this group was associated with persistence of donor major histocompatibility class-II-positive hematolymphoid cells, including OX62+ donor dendritic cells. This study offers insights into two different aspects of chronic rejection: 1) possible mechanisms underlying the persistent immunological injury and 2) the association between immunological injury and the development of obliterative arteriopathy. Based on the findings, it is not unreasonable to raise the testable hypothesis that direct presentation of alloantigen by donor antigen-presenting cells is required for long-term, chronic-rejection-free allograft acceptance. In addition, chronic intermittent lymphatic disruption is implicated as a possible mechanism for the association between chronic interstitial allograft inflammation and the development of obliterative arteriopathy.

Stress protein research in transplantation. Report on presentations at the Fourth Basic Sciences Symposium of the Transplantation Society

No Abstract Available

Obliterative bronchiolitis after lung and heart-lung transplantation. An analysis of risk factors and management

With a prevalence of 34% (55/162 at-risk recipients) and a mortality of 25% (14/55 affected recipients), obliterative bronchiolitis is the most significant long-term complication after pulmonary transplantation. Because of its importance, we examined donor-recipient characteristics and antecedent clinical events to identify factors associated with development of obliterative bronchiolitis, which might be eliminated or modified to decrease its prevalence. We also compared treatment outcome between recipients whose diagnosis was made early by surveillance transbronchial lung biopsy before symptoms or decline in pulmonary function were present versus recipients whose diagnosis was made later when symptoms or declines in pulmonary function were present. Postoperative airway ischemia, an episode of moderate or severe acute rejection (grade III/IV), three or more episodes of histologic grade II (or greater) acute rejection, and cytomegalovirus disease were risk factors for development of obliterative bronchiolitis. Recipients with obliterative bronchiolitis detected in the preclinical stage were significantly more likely to be in remission than recipients who had clinical disease at the time of diagnosis: 81% (13/15) versus 33% (13/40); p < 0.05). These results indicate that acute rejection is the most significant risk factor for development of obliterative bronchiolitis and that obliterative bronchiolitis responds to treatment with augmented immunosuppression when it is detected early by surveillance transbronchial biopsy.

Phenotypic and functional characteristics of colonic lymphocytes isolated from patients with primary sclerosing cholangitis and inflammatory bowel disease

Because primary sclerosing cholangitis (PSC) frequently is associated with inflammatory bowel disease, the phenotypic and functional characteristics of lymphocytes isolated from colonic mucosa were studied in patients with primary sclerosing cholangitis (PSC), patients with ulcerative colitis and patients with other colonic and hepatic disorders. To accomplish this, lymphocytes isolated from colonic biopsies obtained at the time of colonoscopy were expanded in vitro in the presence of interleukin 2 (IL2). Cell propagation was similar in patients with PSC with or without associated inflammatory bowel disease but was diminished significantly when compared to results obtained in patients with ulcerative colitis not associated with PSC. The CD4:CD8 ratio of the propagated lymphocytes was increased in patients with PSC compared to controls. The Leu 19+ subset of cells was also increased in PSC patients. In patients with inflammatory bowel disease, increased cytotoxicity was noted at low effector to target cell ratios with SK-HEP (hepatocellular carcinoma) but not RPMI 7451 (cholangiocarcinoma) targets. No differences between PSC patients and controls were observed for NK sensitive and NK resistant targets. Based upon these studies it can be concluded that: 1) expansion of lymphocytes obtained from endoscopic colonic biopsies using recombinant IL2 represents an alternative method by which intestinal lymphocytes can be studied; 2) natural killer cells are increased in the colonic mucosa of patients with primary sclerosing cholangitis; 3) colonic cytotoxic T lymphocytes may be more active in patients with chronic liver disease and particularly those with associated inflammatory bowel disease.

Expression of stress proteins and lymphocyte reactivity in heterotopic cardiac allografts undergoing cellular rejection

This report addresses the concept that, during rejection, the allograft undergoes a stress response which leads to an increased expression of stress proteins, also called heat shock proteins (hsp), and the recruitment and activation of hsp-reactive lymphocytes. Recent studies in our laboratory have provided evidence that hsp-reactive T-cells are present in cardiac allografts undergoing rejection. In this study, an MHC incompatible heterotopic heart allograft model (ACI into LEW) was chosen to analyse the kinetics of hsp expression during the development of rejection. Allografts and syngrafts (LEW into LEW) were harvested every day during the first 5 days post-transplant. Immunoblot analysis of proteins extracted from graft stromal tissues was done with murine monoclonal antibodies (mAb) against various mammalian hsp. Proliferation studies were done to determine hsp reactivity of graft-infiltrating lymphocytes on different days post-transplant. Three types of stressful stimuli appeared to increase hsp expression in the allograft. The first was a physiological stress secondary to the trauma of the transplant procedure and ischaemia/reperfusion injury and this would occur in allogeneic and syngeneic grafts. During the first day after transplantation, both types of grafts showed higher expression of hsp72 and grp78 and to a lesser extent, hsp60 and grp75. On the second and third day, the expression of grp78 and grp96 was higher in allografts than in syngrafts and this may reflect an immunologically mediated stress response in the allograft when infiltrating hsp-reactive lymphocytes became first detectable in the allograft. The third type of stress appeared related to the inflammatory process associated with rejection. On the fourth and fifth day post-transplant, the allografts showed strong expression of at least five proteins of lower molecular mass reacting with hsp-specific mAbs; namely, approximately 40 kDa (detected by anti-hsp60), approximately 30 kDa (by anti-hsp72), approximately 45 kDa and approximately 32 kDa (by anti-hsp72 + hsc73), and approximately 50 kDa (by anti-grp78). At that time, the allograft began to show progressive inflammatory changes and tissue damage. The appearance of lower molecular mass hsp-crossreactive proteins might reflect a degradation of hsps which had increased expression earlier during the post-transplant period. This process may generate large quantities of hsp-derived peptides which may be presented by MHC molecules to graft-infiltrating T-cells. Another interpretation of the strong expression of lower molecular bands in later allografts is that they represent other stress proteins that crossreact with antibodies against hsp60 and hsp70 family members.(ABSTRACT TRUNCATED AT 400 WORDS)

Immunoglobulin G lymphocytotoxic antibodies in clinical liver transplantation: studies toward further defining their significance

Twenty-two consecutive liver allograft recipients, who tested positive for immunoglobulin G (IgG) lymphocytotoxicity were subjected to pretransplantation and posttransplantation immunologic monitoring of anti-donor IgG lymphocytotoxic antibody titers, total hemolytic complement activity (CH100), circulating immune complexes (CIC), and platelet counts in an effort to improve our understanding of the preformed antibody state in clinical hepatic transplantation. Ten contemporaneous liver transplant recipients whose crossmatch results were negative and who experienced severe hepatocellular damage early after transplantation were included as controls. Crossmatch test results were negative 1 day after transplantation and during the 1 month follow-up remained negative in 14 of 22 (64%) sensitized recipients, most of whom had relatively low (< or = 1:16) anti-donor IgG antibody titers before transplantation. After transplantation, this group and the control group experienced no thrombocytopenia, no increase of CIC, and a gradual increase in CH100 activity that reached normal levels within 1 week. A strong negative correlation between prothrombin time (PT) and CH100 activity in these groups of patients suggested that changes in CH100 activity (P < .0005) were tightly linked to liver synthetic function. In contrast, the crossmatch test results remained positive after transplantation in 8 of 22 (36%) sensitized recipients, all of whom had relatively high (> 1:32 to 1024) pretransplantation titers of anti-donor IgG antibodies. After transplantation these patients developed a syndrome that was characterized by decreased CH100 activity and increased CIC compared with pretransplantation levels and refractory thrombocytopenia that was associated with a 50% allograft failure rate because of biopsy-proven humoral and acute (cellular) rejection.(ABSTRACT TRUNCATED AT 250 WORDS)

Heat shock protein-induced T-lymphocyte propagation from endomyocardial biopsies in heart transplantation

BACKGROUND

Recent studies have shown that heat shock proteins can be recognized by T cells during various immunologically mediated inflammatory processes. Injurious stimuli to cells induce an increased production of heat shock proteins which could lead to their cell surface expression and subsequent recognition by the immune system. We have postulated that allograft infiltrating cells may recognize heat shock proteins, especially during rejection.

METHODS

This hypothesis was tested by incubating heart transplant biopsy specimens from 89 heart transplant recipients with soluble Mycobacterium tuberculosis extracts, a source of heat shock proteins or recombinant mycobacterial heat shock protein 65. T cell phenotypes were determined by flow cytometry.

RESULTS

Mycobacterium tuberculosis extract can induce lymphocyte propagation from heart transplant biopsy specimens especially during rejection. A highly significant correlation was seen between Mycobacterium tuberculosis extract and interleukin-2-induced lymphocyte growth and an accelerated growth was seen for cultures incubated with Mycobacterium tuberculosis extract + interleukin-2. A second series of experiments has also shown the propagation of lymphocytes induced by recombinant mycobacterial heat shock protein-65. T-cell phenotype analysis of biopsy propagated lymphocytes has shown higher frequencies of CD8 cells in Mycobacterium tuberculosis extract and heat shock protein-65 propagated lymphocytes from early posttransplantation biopsy specimens, whereas, later on, most cultures showed a predominance of CD4 cells. T-cell receptor gamma delta cells were more frequently found in biopsy-derived lymphocyte cultures from long-term survivors, especially after propagation with Mycobacterium tuberculosis extract and heat shock protein-65. These gamma delta cells expressed primarily the delta 1 rather than the gamma 9 phenotype.

CONCLUSIONS

These observations provide first evidence for the presence of heat shock protein-reactive lymphocytes in cellular infiltrates of transplants undergoing rejection.

Immunopathology of cardiac transplant rejection

Transplant rejection represents a diverse series of complex immunological events beginning with allorecognition and lymphocyte activation and differentiation, followed by interactions of antibodies and activated lymphocytes with the vascular endothelium and subsequent cellular infiltration into the allograft, and, finally, the inflammatory process leading to tissue injury. This paper reviews how these events contribute to the different types of cardiac transplant rejection, including cardiac allograft vasculopathy.

Heat shock protein reactivity of lymphocytes isolated from heterotopic rat cardiac allografts

Although it is well known that cellular rejection is mediated by alloreactive lymphocytes, several investigators, including our group, have shown that such cells are a rather small proportion of the T cell infiltrate of the alolograft. We have therefore postulated that graft-infiltrating lymphocytes must recognize other antigens. Since heat shock protein (hsp)-specific lymphocytes have been shown to participate in several autoimmune diseases and in tumor immunity, we hypothesized that hsp-reactive lymphocytes are involved with allograft rejection. This hypothesis was tested with a rat model of heterotopic MHC-incompatible cardiac allografts (ACI into Lewis), whereby graft-infiltrating lymphocytes and spleen cells were tested in vitro with different recombinant mycobacterial hsp preparations. As expected, allograft lymphocytes showed proliferative responses to irradiated spleen cells from the donor. This proliferation was markedly augmented by hsp65 (3-fold) and hsp70 (5-fold), whereas hsp10 and the protein control ovalbumin had no effect. Proliferation of allograft lymphocytes to hsp in context with syngeneic splenocytes as antigen-presenting cells (APC) was seen primarily if small quantities of IL-2 had been added to the cultures. In contrast, hsp-specific proliferation was never observed with syngraft lymphocytes, even after addition of IL-2. Spleen cells from allograft and syngraft recipients showed hsp augmentation of alloproliferation, but the magnitude was less than that with allograft lymphocytes. Kinetic studies showed that hsp-reactive lymphocytes first appeared in the allograft on day 3 posttransplant. Tacrolimus immunosuppression of transplant rejection prevented the appearance of hsp-reactive lymphocytes in allografts. Culture conditions have been established to generate hsp65- and hsp70-specific T lymphocyte lines and clones from allograft-infiltrating cells. These cultured cells exhibited hsp reactivity only in context with self-APC, and this was augmented by small amounts of IL-2. These data provide strong evidence for the involvement of hsp-reactive lymphocytes in allograft rejection. We propose the concept that during rejection tissue stress induced by alloreactive effector lymphocytes promotes the recruitment and activation of hsp-reactive lymphocytes, especially in the presence of IL-2 released into the allogeneic environment of the transplant. These hsp-reactive T cells may play a role in the immune cascade of the inflammatory process of transplant rejection.

Cytokine mRNA profiles in mouse orthotopic liver transplantation. Graft rejection is associated with augmented TH1 function

Although mouse liver allografts are spontaneously accepted without immunosuppression in many strain combinations, rejection can be induced by presensitization with a donor skin graft two weeks prior to transplantation. In this study, the semiquantitative reverse transcription polymerase chain reaction (RTPCR) was used to assess the involvement of T helper (TH) cell subsets in liver allograft acceptance by determining cytokine mRNA in the graft and spleen of recipients with (A) spontaneously accepting allografts (B) rejecting liver allografts after previous skin sensitization, and (C) syngeneic controls. Spontaneously accepted liver allografts showed upregulation of TH1 (IL-2, IFN-gamma) and TH2 (IL-4, IL-10) intragraft cytokine mRNA, which peaked at day 6 and tapered off thereafter, when compared with levels in syngeneic grafts, but both IFN-gamma and IL-10 mRNA persisted up to day 30. This cytokine mRNA profile correlated with the transient intragraft inflammation associated with spontaneously resolving rejection. Presensitized recipients that rejected their grafts revealed marked upregulation of TH1 (IL-2 and IFN-gamma) and TH2 (IL-4, IL-6) intragraft cytokine mRNAs compared with spontaneously accepting recipients, although IL-10 mRNA levels showed no differences between the two groups. The most striking difference was seen in IFN-gamma levels, which correlated well with the preferential deposition of IgG2a antibody isotype in the rejecting compared with the spontaneously accepting liver allograft recipients. These results suggested an association between liver allograft rejection and enhanced TH1 cytokine immune response. The ability to reject liver allografts by the adoptive transfer of splenocytes, but not serum, from a sensitized mouse ruled out preformed antibodies alone as a cause of rejection. However, spleen cytokine mRNA profiles showed no differences or trends in TH1 or TH2 expression in spontaneously accepting versus rejecting recipients, which suggested that the spleen is not a major site of alloreactive immune expansion. These data suggest that spontaneous acceptance of mouse liver allografts is associated with an insufficient intragraft TH1 cytokine response, the cause of which is currently under investigation.

Progress report on the ASHI/CAP Proficiency Survey Program in Histocompatibility Testing. I. HLA-A,B,C typing, antibody screening, and lymphocytotoxicity crossmatching. American Society for Histocompatibility and Immunogenetics. College of American Pathologists

The Histocompatibility Survey Program was organized in 1982 as a joint project by the ASHI and CAP to evaluate laboratory performance in HLA typing, lymphocytotoxicity crossmatching, and antibody analysis. This report summarizes the experience with the HS surveys on HLA class I serology. During a 12-year period, the number of participating laboratories increased from 150 to 285 and HLA typing was done with 90 survey specimens representing 20 HLA-A and 35 HLA-B antigens. Most unsplit antigens were correctly identified in more than 90% of the laboratories. For many antigens, a high percentage of participants reported a split and there was generally a high consensus of a correct assignment. Nevertheless, several antigens were difficult to define, as shown by low consensus rates. During recent years, the assignments of Bw4/6 and HLA-C antigens have significantly improved. Lymphocytotoxicity crossmatching was analyzed for 138 cell-serum combinations tested by an average of 143 laboratories. Comparisons between four techniques (basic NIH, Amos modified, LI, and AHG) showed consistent results (greater than 90% crossmatch compatibility or incompatibility) for 71% of the cell-serum combinations. The crossmatch results with the remaining combinations were more variable for one or more of the crossmatch techniques. Serum antibody identification showed a continued improvement during recent years, and the average consensus for assigning acceptable antibody specificity reached 88%. A performance grading system based on a 90% consensus rate among participants is used to satisfy requirements for laboratory accreditation.

Progress report on the ASHI/CAP Proficiency Survey Program in Histocompatibility Testing. II. HLA-DR, DQ serologic typing, antibody identification, and B-cell crossmatching. American Society for Histocompatibility of Immunogenetics. College of American Pathologists

This report summarizes the 8-year experience of the DR survey program designed to evaluate the performance of histocompatibility laboratories in the serologic typing of cell specimens for HLA-DR and HLA-DQ polymorphisms and the HLA class II antibody identification and B-cell crossmatching of serum specimens. The number of participants increased from 45 in 1985 to 214 in 1992. Although the performance criteria are based on laboratory consensus, the availability of DNA typing since 1990 has enabled a critical assessment of the reliability of serologic HLA-DR, DQ typing. The survey results shows that unsplit HLA class II antigens DR1-DR8, DR52/53, and DQ1-3 are generally correctly identified in over 90% of the participating laboratories. DR9 and DR10 have not yet been tested and testing for DQ4 has not yet achieved this level on consensus. In contrast, the assignments of serologic subtypes of HLA-DR and HLA-DQ are less consistent and frequently unreliable. Although the B-cell crossmatches show generally high laboratory consensus rates, the serum screening results show frequently inconsistent results regarding HLA class-II-specific antibody identification.

Combined liver-kidney transplantation and the effect of preformed lymphocytotoxic antibodies

Thirty-eight sequentially placed liver and kidney allografts were evaluated with respect to patient and graft survival, and the influence of preformed lymphocytotoxic antibodies was analysed. The results suggest that the survival rate of combined liver and kidney transplantation is similar to the survival rate of liver transplantation alone. Sequentially placed kidney allografts may be protected from hyperacute rejection in the presence of donor specific lymphocytotoxic antibodies, but not in all instances. Both patient and kidney allograft survival was lower in positive crossmatch patients (33% and 17% respectively) than in negative crossmatch patients (78% and 75%). High levels of panel reactive antibodies (> 10%) also appeared to have a deleterious effect on survival, although the majority of the patients who failed also had a positive crossmatch. Although performed lymphocytotoxic antibodies are not an absolute contraindication to combined liver-kidney transplantation, they do appear to have a deleterious effect on long-term graft survival. However, more correlation with clinical parameters is needed.

The influence of HLA matching on cytomegalovirus hepatitis and chronic rejection after liver transplantation

Previous findings in liver transplantation patients have raised the concept that HLA plays a dualistic role. HLA matching will reduce rejection but may augment MHC restricted cellular immune mechanisms of liver allograft injury. To evaluate this concept, we studied CMV hepatitis in 399 FK506-treated liver transplant patients, including 355 cases for which complete HLA-A,B,DR,DQ typing information was available. CMV hepatitis developed in 25 patients, and 17 of them (or 68%) showed a one or two HLA-DR antigen match with the donor. In contrast, HLA-DR matches were found in only 35% of 330 patients without CMV hepatitis (P = 0.005). No significant associations were seen for HLA-A, HLA-B, and HLA-DQ antigens. In pretransplant CMV-seronegative patients with seropositive grafts (n = 39), the frequency of CMV hepatitis was 44% for HLA-DR-matched livers but 14% for HLA-DR-unmatched livers. In seropositive recipients (n = 187), these frequencies were 12% and 2% for HLA-DR-matched and unmatched liver grafts. Chronic rejection developed in 29 patients (or 8%) during a follow-up between 10 and 24 months after transplantation. Its incidence was higher in the CMV hepatitis group (24% vs. 6%) (P = 0.007). Although no associations were found between HLA matching and the incidence of chronic rejection, there was an earlier onset of chronic rejection of HLA-DR-matched livers irrespective of CMV hepatitis. These findings suggest that an HLA-DR match between donor and recipient increases the incidence of CMV hepatitis in both primary and secondary CMV infections. Although HLA compatibility leads to less acute cellular rejection, it is suggested that DR matching may accelerate chronic rejection of liver transplants, perhaps through HLA-DR-restricted immunological mechanisms toward viral antigens, including CMV.

Serum autoantibody to the nucleolar antigen PM-Scl. Clinical and immunogenetic associations

OBJECTIVE

The inflammatory myopathies are characterized by distinctive autoantibodies that are associated with certain clinical features and immunogenetic patterns. Anti-PM-Scl is one such antibody and is found in pure myositis, myositis in overlap, and systemic sclerosis (SSc). Our purpose was to describe the clinical and immunogenetic associations of the anti-PM-Scl antibody.

METHODS

Serum samples from 617 patients with various connective tissue diseases were screened for anti-PM-Scl antibody by indirect immunofluorescence and Ouchterlony double immunodiffusion. Patients with anti-PM-Scl were serologically typed for HLA-DR and DQ, and the genes encoding DQ alpha and DQ beta were characterized by hybridization of sequence-specific oligonucleotide to amplified genomic DNA.

RESULTS

Twenty-three patients (4%) had serum anti-PM-Scl. Sixteen had either pure myositis or myositis in overlap, 6 had SSc alone, and 1 had SSc and rheumatoid arthritis. Twenty of the antibody-positive patients had serologic HLA typing performed; 15 (75%) were HLA-DR3 positive, and 17 (85%) expressed the DQw2 allele. None of the 5 DR3 negative patients shared a unique DR or DQ antigen with the DR3 positive patients, and further DNA analysis of 10 patients (4 of whom were DR3 negative) did not reveal any unique DQ alleles.

CONCLUSION

Anti-PM-Scl identifies a subset of patients with myositis, SSc, or an overlap of the two disorders, and this antibody has a strong but not exclusive immunogenetic association with the HLA-DR3 antigen.

Mitogen responses of lymphocytes from lung transplant recipients--correlation with rejection and infection

Proliferative responses to nonspecific mitogens were analyzed for 119 bronchoalveolar lavages and 108 concurrent peripheral blood samples from 35 lung transplant patients. The patients were classified at each time as normal, rejecting, or infected on the basis of trans-bronchial biopsy, culture results, clinical signs, and pulmonary function. During rejection episodes the bronchoalveolar lavage responses to concanavalin A and phytohemagglutinin were significantly increased (P less than 0.004 and P less than 0.006, respectively). The differences were less pronounced when rejection occurred within 30 days after bolus immunosuppressive therapy, either as immunoprophylaxis or as treatment for a previous rejection episode, and were not significantly different from normal. Differences in response during rejection were limited to the graft; analysis of circulating T cells was not helpful (P = NS). In contrast, markedly depressed responses to Con A and PHA were seen during infection. Significant differences were observed both in the graft (P less than 0.007) and in circulating lymphocytes (P less than 0.02), suggesting that global depression of mitogen response is associated with immunocompromise. Sequential analysis of 6 patients showed that individual changes in mitogen response paralleled those seen in the population (P less than 0.046, normal vs. rejection and P less than 0.043 normal). These findings suggest that mitogen assays of bronchoalveolar lavage lymphocytes and, to a lesser extent, PBL, are clinically useful in assessing intragraft immunocompetence and in distinguishing rejection from infection in lung transplant patients.

Presence of CD4, CD8 double-negative and T-cell receptor-gamma-delta-positive T cells in lymphocyte cultures propagated from coronary arteries from heart transplant patients with graft coronary disease

Previous studies have shown that the interleukin-2-induced propagation of lymphocytes from endomyocardial biopsy specimens, an indicator of cellular rejection, is associated with the development of graft coronary disease in heart transplant patients. To further investigate the concept of cell-mediated immune responses in graft coronary disease, we have applied the methodologies of interleukin-2-induced propagation of lymphocytes from arterial tissues. In a group of 23 patients, which included 6 heart, 6 kidney, and 11 liver transplant recipients, we observed that arterial lymphocyte growth was significantly associated with obliterative vasculopathy (p less than 0.03). T-cell phenotyping analysis of coronary artery-derived lymphocyte cultures from three heart transplant patients with graft coronary disease showed significant numbers of CD4, CD8 double-negative T cells and T-cell receptor-gamma delta cells, especially when the cultures were established with relatively high doses of 400 U/ml of interleukin-2. These data suggest that the subset of CD4-CD8-, T cell receptor-gamma delta+ T cells may play a role in the pathogenesis and progression of graft coronary disease.