A.R. van der Horst

Pretransplantation Blood Transfusion Revisited

BACKGROUND Blood transfusion before organ transplantation has a beneficial effect on allograft survival; the mechanism of this effect has remained a mystery. In murine models, the presence of common histocompatibility antigens in the blood donor and the recipient favors the induction of allograft tolerance. METHODS To investigate the effect of HLA compatibility between blood donor and recipient on the induction of allograft tolerance, we determined the relative frequency of cytotoxic T-lymphocyte precursors specific for donor cells before and at several times after blood transfusion in 23 patients awaiting a first renal transplant. We correlated the results with the presence of shared HLA antigens. RESULTS T-cell nonresponsiveness against donor cells developed after blood transfusion in 10 of the 23 patients. Tolerance developed only if the blood donor and the recipient had one HLA haplotype or at least one HLA-B and one HLA-DR antigen in common (as was observed in 9 of these 10 patients). Tolerance developed relatively late after blood transfusion (one to two months) and was long-lasting. No decline in the T-cell response against donor alloantigens was observed in any of the 13 patients who received transfusions without having HLA-antigen compatibility with the donor. CONCLUSIONS Blood transfusion in which there is a common HLA haplotype or shared HLA-B and HLA-DR antigens induces tolerance to donor antigens. This finding may lead to the development of new strategies with which to induce tolerance for transplantation after blood transfusion. Perhaps transplant donors will be selected not only by HLA-antigen matching, but also on the basis of acceptable HLA-antigen mismatches associated with T-cell non-responsiveness induced by selected blood transfusion.

HLA typing in congenital toxoplasmosis.

HLA-A, HLA-B, HLA-C, and HLA-D typing was performed in 47 mothers of patients suffering from ocular toxoplasmosis to investigate whether an immunogenetic predisposition exists for developing congenital toxoplasmosis in their offspring. No significant association between any HLA antigen was observed in the mothers of patients with ocular toxoplasmosis, although a total absence of the HLA-B51 antigen was found in this group. HLA-A, HLA-B, and HLA-C typing was also performed in their children (52 patients with ocular toxoplasmosis), to investigate a possible relation between the severity of ocular toxoplasmosis and an eventual immunogenetic factor. In the patients with ocular toxoplasmosis an increased frequency of the HLA-Bw62 antigen was observed in correlation with severe ocular involvement.

The role of MHC class I heterodimer expression in mouse ankylosing enthesopathy

Abstract Ankylosing enthesopathy (ANKENT) is a spontaneous mouse joint disease with strikingly similar pathology to human HLA-B27-associated enthesopathies such as ankylosing spondylitis. In C57Bl/10 mice, transgenic HLA-B*2702 as well as H2 genes have been shown to be relative risk factors for ANKENT. To investigate the role of major histocompatibility complex (MHC) class I expression in disease pathogenesis, ANKENT occurrence was compared among β2-microglobulin (β2m) knockout littermates with or without transgenes for HLA-B*2702 and human β2m. In the knockout phenotype lacking β2m, ANKENT occurrence is significantly reduced (P = 0.016). In the absence of β2m, B*2702 is not detected on the cell membrane, nor does it increase the risk for ANKENT. This means that the previous finding that HLA-B*2702 increases susceptibility to ANKENT in C57Bl/10 mice cannot be ascribed to a transgene insertion effect. Rather, in order to increase disease susceptibility, B*2702 must be coexpressed with mouse β2m (mo-β2m). In contrast, when HLA-B*2702 is expressed with β2m of human origin, disease susceptibility is not affected. Thus, both H2b-derived class I heterodimers and HLA-B*2702/mo-β2m heterodimers contribute to ANKENT susceptibility.

High-affinity cytotoxic T lymphocytes after non-HLA-sharing blood transfusion--the other side of the coin.

Previously, we have shown that pretransplantation blood transfusion modulates the T cell repertoire to a great extent. Patients receiving a BT from a donor sharing one HLA haplotype with the patient (HLA-sharing BT) develop CTL nonresponsiveness against cells of the BT donor and show a selective decrease in the usage of T cell receptor V beta families. The present study has focused on the analysis of the T cell repertoire in patients receiving an HLA mismatched (non-HLA-sharing) BT. CTL precursor frequencies were measured against single class I-mismatched antigens in split-well analysis. In addition, blocking studies of CTL-target cell interaction were performed with anti-CD8 monoclonal antibodies. The results demonstrate that non-HLA-sharing BT immunizes and induces the generation of CD8 independent, high-affinity CTL against immunogenic class I-mismatched antigens. Such HLA class I antigens might become nonacceptable mismatches in subsequent organ transplantation.

5' regulatory nucleotide sequence of an HLA-A*0101null allele.

Abstract We have previously demonstrated an HLA-A*0101null allele segregating in a family with the HLA-B8, -Cw7, -DR3, -DR52, -DQ2 haplotype. In the present study the regulatory elements with known transcription enhancement activity of the silenced HLA-A*0101 allele were analyzed. In the enhancer B element, a T was substituted for a C at position  – 106, whereas no other alterations were found in the adjacent 5′ section of the HLA-A*0101null allele. This substitution was not seen in the enhancer B elements of the corresponding genes involved in normal HLA-A*0101 membrane expression. Comparison of enhancer B element sequences of classical functional major histocompatibility complex (MHC) class I alleles demonstrated a high degree of conservation. In contrast, many MHC class I pseudogenes showed mutation in their enhancer B boxes. These results may indicate that the single mutation detected in the enhancer B element plays a pivotal role in the abolishment of membrane expression of the HLA-A*0101null allele.

A new public antigen shared by all HLA-A locus products except HLA-A23, -A24, -A32, and -A25 is probably influenced by the amino acid residue at position 79 in the α1 domain

One of the most striking features of HLA gene products is their high degree of polymorphism. The most effort was aimed at the definition of private HLA antigens, and as a result, almost a hundred HLA alleles received official recognition by the WHO Nomenclature Committee. However, thus far little attention has been focused on the definition and the biological relevance of HLA antigenic determinants, shared among various HLA products. Public HLA specificities have been defined by pregnancy sera and by monoclonal antibodies (mAb) (Konoeda et al. 1986, Parham et al. 1986, Spear et al. 1985). An important reason for defining public HLA specificities is the recognition that public specificities represent polymorphic epitopes that can function as alloantigens. This would have important implications for the study of HLA and disease associations and for transplantation studies (Konoeda et al. 1986). Two of the public HLA determinants first described were the Bw4 and Bw6 specificities (Van Rood 1962). Originally, they were identified by pregnancy sera as products of a diallelic system in genetic linkage with the HLA-B-locus-encoded alloantigens. It was shown that these public determinants were spatially distinct from the private determinants of the H L A B locus alleles (Parham 1983). More recently, it became evident that the expression of Bw4 and Bw6 epitopes is not strictly limited to HLA-B locus antigens. The Bw4 epitope appears to be present on HLA-A23, HLA-A24, and HLA-A32 molecules as well, and HLA-Cw3 carries a determinant related to Bw6 (Muller et al. 1982, Kostyu et al. 1980). In the present study, we describe a new public HLAspecificity recognized by a mouse lymphocytotoxic mAb. This mAb, 3Gl l , is of the IgM isotype and recognizes a determinant shared by all HLA-A locus products with the exception of the Bw4-associated HLA-A antigens.

Influence of HLA-DRB1* incompatibility on the occurrence of rejection episodes and graft survival in serologically HLA-DR-matched renal transplant combinations

BACKGROUND The aim of the present study was to analyze the effect of HLA-DRB1* mismatches on graft function and graft survival in 92 patients who received serologically HLA-DR split antigen-matched cadaveric renal transplants. METHODS The polymorphic second exon of the HLA-DRB1 alleles was typed using the sequence-specific oligonucleotides technique. RESULTS The results show that in 26 of the 92 analyzed combinations, one or more HLA-DRB1* mismatches were found (28%). The analysis of the occurrence of treatable rejection episodes during the first 3 months after transplantation demonstrated a significantly higher incidence of rejection episodes in the HLA-DRB1*-mismatched group: 18 of 26 (69%) in the HLA-DRB1*-mismatched group against 23 of 66 (35%) in the HLA-DRB1*-matched group (P(uncorr)=0.0033). However, no effect of HLA-DRB1* mismatches on graft survival was found, although in general graft survival in the whole patient group was negatively influenced by the occurrence of rejection episodes during the first 3 months after transplantation (P(uncorr)=0.0008). In contrast, in the HLA-DR4-matched donor-recipient combinations (n=28), the effect of mismatching for the HLA-DRB1*04 alleles seemed to have a pronounced effect not only on the occurrence of rejection episodes but also in the form of diminished graft survival. CONCLUSIONS Thus, this study indicates that the existence of HLA-DRB1* allele mismatches in renal transplant recipients, matched for the serologically defined HLA-DR split antigens, is not harmful for the transplant. The exception is the HLA-DRB1*04 mismatch, which seems to be deleterious for the grafted organ.

Fine specificity of the alloantiserum MSD-51 : epitope mapping of HLA-DRw53 determinants

HLA-DRw53 is a supertypic specificity expressed by HLA-DR4-, HLA-DR7-, and HLA-DR9-positive cells. In the present study, the fine specificity of an HLA-DRw53-specific alloantiserum (MSD-51) was analyzed in serology and by the isoelectric focusing technique. In serology, MSD-51 recognized HLA-DRw53-positive cells with the exception of cells expressing the HLA-DR7/DRw53/DQw9 haplotype. The immunoprecipitation studies and the use of the IgM-reducing agent dithiothreitol revealed that MSD-51 consisted of at least two antibodies: (1) an IgM antibody which reacted with the HLA-DRB4 gene product of HLA-DRw53-positive cells, except HLA-DR7/DRw53/DQw9-expressing cells, and (2) at least one IgG antibody which recognized a linear sequence or conformational structure formed by positions 67 to 70 on the HLA-DRB1 gene product of HLA-DR4- and HLA-DR9-positive cells. These findings demonstrate the complexity of the supertypic HLA-DRw53 antigen analyzed with a serologically well-defined HLA-DRw53-specific alloantiserum.

Effect of a Tyr-to-His Point-mutation at Position 59 in the Alpha-1 Helix of the HLA-B27 Class-I Molecule on Allospecific and Virus-specific Cytotoxic T-lymphocyte Recognition

HLA-B2703, a mutation of HLA-B2705, is characterized by a Tyr-to-His substitution at position 59 in the alpha 1 domain of the class-I heavy chain. So far, the HLA-B2703 subtype was found only in two Black individuals and it is the first polymorphism at position 59 of MHC class-I molecules. We have examined whether the single amino-acid substitution at position 59 results in an alloantigenic determinant and HLA-restriction element, and whether HLA-B2703 functionally differs from HLA-B2705. In vitro, HLA-B2703-positive lymphocytes were not stimulated by HLA-B2705-positive cells. Nevertheless, HLA-B2703 was recognized as an alloantigen. HLA-B2702-anti-HLA-B2705 CTL lysed HLA-B2703-positive cells less efficiently than HLA-B2705-positive cells. In addition, anti-HLA-B27 antibodies were found that lysed HLA-B2705 but not HLA-B2703 positive cells. Also, CTL clones have been described that can distinguish HLA-B2703 from HLA-B2705 (1). However, the HLA-B2703 subtype did not function as a private virus restriction element. HLA-B2705-restricted influenza virus-specific CTL also recognized HLA-B2703-positive virus-infected cells, and vice versa. Thus, the HLA-B2703 mutation represents an example of a class-I antigen without specific significance for the recognition of viral peptides.

Antigen Society #13 Report (B7, B27, Bw47, Bw73): Public Determinants of the HLA-B7 CREG Defined by Antibodies and T-Cell Clones

We have previously described a fine-specificity analysis of a series of HLA-B7 allospecific CTL clones (*1). Besides an HLA-B7-specific reactivity, these CTL clones exerted distinct “extra reactions,” i.e., lysis of some non-B7 target cells. These extra reactivities showed a remarkable resemblance with the well-known compartments of the cross-reacting group of HLA-B7 (B7-CREG) as defined by antibodies. We therefore extended the fine-specificity analysis of our B7-specific CTL clones by studying the reactivity patterns of the clones on a combined panel of cell lines from the Workshop (WS) and of local source. The CTL clones KOR-1, KOR-18, KOR-132, HG-31, HG-61, and LIV-8 were isolated by limiting dilution procedures from an MLC stimulation. All clones were derived from stimulation with cells that were either HLA-B7 homozygous or het- erozygous HLA-B7, B44, while the clones themselves all express HLA-B60 and B44 (*1). Thus, there may be a bias in the reaction patterns of the clones because of the self-tolerance for a part of the B7-CREG, which includes B60.