Characterization of the novel HLA-B*07:491 allele by next generation sequencing

HLA-B*07:491 differs from HLA-B*07:02:01 by one nucleotide substitution in codon 218 in exon 4.

Characterization of the novel HLA-B*07:482 allele using next-generation sequencing methods

HLA-B*07:482 differs from HLA-B*07:02:01:01 allele by one nucleotide substitution in codon 285 in exon 5.

Paradoxical Effects of Endoplasmic Reticulum Aminopeptidase 1 Deficiency on HLA-B27 and Its Role as an Epistatic Modifier in Experimental Spondyloarthritis

OBJECTIVE

We undertook this study to examine the functional basis for epistasis between endoplasmic reticulum aminopeptidase 1 (ERAP1) and HLA-B27 in experimental spondyloarthritis (SpA).

METHODS

ERAP1-knockout rats were created using genome editing and bred with HLA-B27/human β2 -microglobulin-transgenic (HLA-B27-Tg) rats and HLA-B7-Tg rats. The effects of ERAP1 deficiency on HLA allotypes were determined using immunoprecipitation and immunoblotting, flow cytometry, allogeneic T cell proliferation assays, and gene expression analyses. Animals were examined for clinical features of disease, and tissue was assessed by histology.

RESULTS

ERAP1 deficiency increased the ratio of folded to unfolded (β2 m-free) HLA-B27 heavy chains, while having the opposite effect on HLA-B7. Furthermore, in rats with ERAP1 deficiency, HLA-B27 misfolding was reduced, while free HLA-B27 heavy chain dimers on the cell surface and monomers were increased. The effects of ERAP1 deficiency persisted during up-regulation of HLA-B27 and led to a reduction in endoplasmic reticulum stress. ERAP1 deficiency reduced the prevalence of arthritis in HLA-B27-Tg rats by two-thirds without reducing gastrointestinal inflammation. Dendritic cell abnormalities attributed to the presence of HLA-B27, including reduced allogeneic T cell stimulation and loss of CD103-positive/major histocompatibility complex class II-positive cells, were not rescued by ERAP1 deficiency, while excess Il23a up-regulation was mitigated.

CONCLUSION

ERAP1 deficiency reduced HLA-B27 misfolding and improved folding while having opposing effects on HLA-B7. The finding that HLA-B27-Tg rats had partial protection against SpA in this study is consistent with genetic evidence that loss-of-function and/or reduced expression of ERAP1 reduces the risk of ankylosing spondylitis. Functional studies support the concept that the effects of ERAP1 on HLA-B27 and SpA may be a consequence of how peptides affect the biology of this allotype rather than their role as antigenic determinants.

Antigen-guided depletion of anti-HLA antibody-producing cells by HLA-Fc fusion proteins

Platelet transfusion and transplantation of allogeneic stem cells and solid organs are life-saving therapies. Unwanted alloantibodies to nonself human leukocyte antigens (HLAs) on donor cells increase the immunological barrier to these therapies and are important causes of platelet transfusion refractoriness and graft rejection. Although the specificities of anti-HLA antibodies can be determined at the allelic level, traditional treatments for antibody-mediated rejection nonselectively suppress humoral immunity and are not universally successful. We designed HLA-Fc fusion proteins with a bivalent targeting module derived from extracellular domains of HLA and an Fc effector module from mouse IgG2a. We found that HLA-Fc with A2 (A2Fc) and B7 (B7Fc) antigens lowered HLA-A2- and HLA-B7-specific reactivities, respectively, in sera from HLA-sensitized patients. A2Fc and B7Fc bound to B-cell hybridomas bearing surface immunoglobulins with cognate specificities and triggered antigen-specific and Fc-dependent cytotoxicity in vitro. In immunodeficient mice carrying HLA-A2-specific hybridoma cells, A2Fc treatment lowered circulating anti-HLA-A2 levels, abolished the outgrowth of hybridoma cells, and prolonged survival compared with control groups. In an in vivo anti-HLA-A2-mediated platelet transfusion refractoriness model, A2Fc treatment mitigated refractoriness. These results support HLA-Fc being a novel strategy for antigen-specific humoral suppression to improve transfusion and transplantation outcomes. With the long-term goal of targeting HLA-specific memory B cells for desensitization, further studies of HLA-Fc's efficacy in immune-competent animal models are warranted.

HLA-B*07:02 and HLA-C*07:02 are associated with trimethoprim-sulfamethoxazole respiratory failure

We have identified an underrecognized severe adverse drug reaction (ADR) of trimethoprim-sulfamethoxazole (TMP-SMX) associated respiratory failure in previously healthy children and young adults. We investigated potential genetic risk factors associated with TMP-SMX induced respiratory failure in a cohort of seven patients. We explored whole genome sequence among seven patients representing nearly half of all reported cases worldwide and 63 unrelated control individuals in two stages: (1) human leukocyte antigen (HLA) locus variation as several other ADRs have been associated HLA genetic variants and (2) coding variation to catalog and explore potential rare variants contributing to this devastating reaction. All cases were either heterozygous (carriers) or homozygous for the common HLA-B*07:02-HLA-C*07:02 haplotype. Despite the small sample size, this observation is statistically significant both in conservative comparison to maximum reported population frequencies (binomial P = 0.00017 for HLA-B and P = 0.00028 for HLA-C) and to our control population assessed by same HLA genotyping approach (binomial P = 0.000001 for HLA-B and P = 0.000018 for HLA-C). No gene elsewhere in the genome harnessed shared rare case enriched coding variation. Our results suggests that HLA-B*07:02 and HLA-C*07:02 are necessary for a patient to develop respiratory failure due to TMP-SMX.

The novel allele, HLA-B*07:68:02, identified in a German cord blood donor and her father

The novel allele HLA-B*07:68:02 identified in two related individuals of Caucasian origin is described.

Public TCR use by herpes simplex virus-2-specific human CD8 CTLs

Recombination of germline TCR alpha and beta genes generates polypeptide receptors for MHC peptide. Ag exposure during long-term herpes simplex infections may shape the T cell repertoire over time. We investigated the CD8 T cell response to HSV-2 in chronically infected individuals by sequencing the hypervariable regions encoding TCR alpha and beta polypeptides from T cell clones recognizing virion protein 22 aa 49-57, an immunodominant epitope. The most commonly detected TCRBV gene segment, found in four of five subjects and in 12 of 50 independently derived T cell clones, was TCRBV12-4. Nineteen to seventy-two percent of tetramer-binding cells in PBMCs were stained ex vivo with a TCRBV12 mAb. Three alpha-chain and three beta-chain public TCR sequences were shared between individuals. Public heterodimers were also detected. Promiscuous pairing of a specific TCRVA1-1 sequence with several different TCRB polypeptides was observed, implying a dominant structural role for the TCRA chain for these clonotypes. Functional avidity for cytotoxicity and IFN-gamma release was relatively invariant, except for one subject with both high avidity and unique TCR sequences and lower HSV-2 shedding. These data indicate that the CD8 response to a dominant alpha-herpesvirus epitope converges on preferred TCR sequences with relatively constant functional avidity.

Cytomegalovirus-specific CD8(+) T cells targeting different HLA/peptide combinations correlate with protection but at different threshold frequencies

Cytomegalovirus (CMV) causes significant morbidity and mortality in patients after haematopoietic stem cell transplantation (HSCT). Due to limitations of current antiviral therapies, alternative approaches, involving transfer of donor-derived CMV-specific CD8(+) T cells, have been considered. Levels of such cells correlating with protection against CMV infection and disease have only been reported in patients expressing HLA-A*0201 and HLA-B*0702. This is despite an increasing number of reports describing cells targeting CMV peptides presented by other human leucocyte antigens (HLAs). Considering several frequent HLA alleles, our findings suggest that HLA-A*2402/pp65 (341-349)- and HLA-B*3501/pp65 (123-131)-specific CD8+ T cells correlate with protection from CMV reactivation at significantly lower cell levels than HLA-A*0101/pp50 (245-253)- and HLAA* 0201/pp65 (495-503)-specific CD8+ T cells, both in HSCT recipients posttransplant and in healthy CMV seropositive volunteers. This may result from a differing efficiency of the responses restricted by the two sets of HLA alleles. These findings add to the knowledge of immunodominance and differences in antigen processing that are coordinated in individuals with different HLA alleles and have direct implications for therapy and monitoring in patients.

Two new cases of familial hairy cell leukemia associated with HLA haplotypes A2, B7, Bw4, Bw6

Hairy cell leukemia (HCL) is a rare hematological disorder of unknown origin. Thirteen familial cases of HCL have been reported, with 28 relatives affected. Here we report 2 cases of HCL in a family associated with HLA haplotypes A2, B7 and Bw4/6.

HLA-B*27/HLA-B*07 in combination with D6S273-134 allele is associated with increased susceptibility to juvenile spondyloarthropathies

OBJECTIVE

Juvenile spondylarthropathies (jSpA) are polygenic and the clustering of disease in families is caused mainly by genetic factors. Our aim was to look for possible associations of other HLA-A and B specificities, MICA and D6S273 microsatellite polymorphisms that might play a role in determining the susceptibility to jSpA.

PATIENTS AND METHODS

jSpA were diagnosed in 74 Croatian children, and 169 healthy unrelated individuals served as the control group. HLA class I (A, B) typing of all individuals was performed, and HLA-B7 and HLA-B27 positive subjects were subtyped by PCR-SSP method. MICA and D6S273 microsatellites alleles were analyzed by electrophoresis in an automated sequencer.

RESULTS

We identified 26 HLA-B*07 and 31 HLA-B*27 positive patients with jSpA. DNA subtyping of HLA-B*27 specificity demonstrated only two subtypes, B*2702 (19.35%) and B*2705 (80.65%), among jSpA patients. Subtyping analysis of HLA-B*07 gene showed presence of only one subtype, B*0702. The OR for HLA-B*07 was 2.61, while the highest OR for a single HLA specificity was found for HLA-B*27 (OR=5.60). The HLA-B*07/B*27 combination found in six children showed higher risk (OR=14.82), but the combination of specificities: HLA-B*07/HLA-B*27, and D6S273-134 allele demonstrated the highest risk (OR=26.83). The association with D6S273-134 allele was not a result of the linkage disequilibrium with HLA-B*27 specificity (LD=-0.5).

CONCLUSION

Our findings provide evidence that HLA-B*27/HLA-B*07 in combination with D6S273-134 allele is associated with increased susceptibility to jSpA in Croatian children.

Predisposition to HPV16/18-related cervical cancer because of proline homozygosity at codon 72 of p53 among Indian women is influenced by HLA-B*07 and homozygosity of HLA-DQB1*03

This study was undertaken to examine whether predisposition to human papillomavirus (HPV)16/18-related cervical cancer (CaCx) because of p53 proline homozygosity (Pro72Pro) among Indian women was mediated singly or jointly with immunogenetic risk factors such as HLA-B*07 or homozygosity of HLA-DQB1*03. Molecular detection of all three genetic factors was performed by polymerase chain reaction-restriction fragment length polymorphism using DNA from (i) 114 CaCx samples (78 HPV16/18 positive) and (ii) 195 cytologically normal cervical scrapes (116 HPV-negative and 79 HPV16/18-positive samples). Multiple logistic regression analyses were performed to examine independent effects of the three factors and to determine age-adjusted odds ratio (OR) [95% confidence interval (CI)] and P-values. HLA-B*07 was observed to be significantly associated with HPV16/18 infection in asymptomatic controls (OR(age-adjusted) = 4.73; 95% CI: 1.55-14.45; P = 0.006) and CaCx (OR(age-adjusted) = 6.14; 95% CI: 2.15-17.53; P < 0.001) in this enhanced sample set of CaCx cases. There was a lack of association between HLA-B*07 and HLA-DQB1*03 in our study samples. The association of p53Pro72Pro with CaCx was non-significant in the absence of HLA-B*07 in HPV16/18-positive women. In this group, prevalence of p53Pro72Pro and HLA-B*07 together was significantly higher (7.0%) among CaCx cases (OR(age-adjusted) = 14.05; 95% CI: 1.11-177.30; P = 0.04), compared with controls (1.3%) lacking both factors. HLA-DQB1*03 homozygosity (OR(age-adjusted) = 4.75; 95% CI: 1.17-19.30; P = 0.03) or p53Pro72Pro (OR(age-adjusted) = 5.84; 95% CI: 1.18-28.99; P = 0.03) was found to be significantly associated with CaCx, each in the absence of the other in this group but not when present jointly in contrast to those lacking both factors (P = 0.214). Thus, modulation of p53Pro72Pro-mediated susceptibility to CaCx by immunogenetic factors could possibly be mediated through cross talk between HPV16/18-induced immune evasion and cell transformation.

HLA-B*0749N: the first HLA-B*07 null allele

In the present article, we report the identification of the first HLA-B*07 null allele found in a Polish patient awaiting a kidney allograft. A discrepant result obtained between serological typing (HLA-B "blank") and high-resolution molecular typing using PCR-SSP method (HLA-B*070201 allele) suggested the presence of a null allele. Genomic DNA sequencing of the HLA-B*07 allele revealed a single nucleotide substitution at the 3' end of the exon 4 leading to a premature stop codon.

Pathology and pathogenesis of severe acute respiratory syndrome

Severe acute respiratory syndrome (SARS) is an emerging infectious viral disease characterized by severe clinical manifestations of the lower respiratory tract. The pathogenesis of SARS is highly complex, with multiple factors leading to severe injury in the lungs and dissemination of the virus to several other organs. The SARS coronavirus targets the epithelial cells of the respiratory tract, resulting in diffuse alveolar damage. Several organs/cell types may be infected in the course of the illness, including mucosal cells of the intestines, tubular epithelial cells of the kidneys, neurons of the brain, and several types of immune cells, and certain organs may suffer from indirect injury. Extensive studies have provided a basic understanding of the pathogenesis of this disease. In this review we describe the most significant pathological features of SARS, explore the etiological factors causing these pathological changes, and discuss the major pathogenetic mechanisms. The latter include dysregulation of cytokines/chemokines, deficiencies in the innate immune response, direct infection of immune cells, direct viral cytopathic effects, down-regulation of lung protective angiotensin converting enzyme 2, autoimmunity, and genetic factors. It seems that both abnormal immune responses and injury to immune cells may be key factors in the pathogenesis of this new disease.

HLA-B locus in Caucasian patients with carbamazepine hypersensitivity

BACKGROUND

A strong pharmacogenetic association has been reported in Chinese patients between human leukocyte antigen (HLA)-B*1502 and carbamazepine (CBZ)-induced Stevens-Johnson syndrome (SJS).

METHODS

We have genotyped the HLA-B alleles in 56 Caucasian patients with varying severities of CBZ hypersensitivity and 43 controls on CBZ without adverse effects.

RESULTS

None of our patients (including two with blistering skin rashes) were positive for the HLA-B*1502 allele. HLA-B*0702 allele may protect against severe CBZ hypersensitivity but warrants further study. Of secondary interest, the correlation between HLA-B*0801 and HLA-DR3, DQ2 and TNF -308 alleles (on the ancestral haplotype 8.1) is consistent with our previous findings.

CONCLUSION

HLA-B*1502 does not seem to be a marker for all forms of CBZ-induced hypersensitivity in a Caucasian population.

Optimized vaccination regimen linked to exhaustive screening approaches identifies 2 novel HLA-B7 restricted epitopes within hepatitis C virus NS3 protein

Broad immune responses, in particular specific for the NS3 protein and mediated by both CD8+ and CD4+T lymphocytes, are thought to play a critical role in the control of hepatitis C virus (HCV) infection. In this study, we searched for novel HLA-B*0702 NS3 restricted epitopes following an optimized NS3NS4 immunization protocol in transgenic mice expressing HLA-B*0702 molecule. Combining predicted and overlapping peptides, we identified two novel epitopes, WPA10 (aa 1111-1120) and LSP10 (aa 1153-1162), which triggered significant IFN-gamma-producing T cell frequencies and high CTL responses. Both epitopes were shown to be immunogenic when used as synthetic peptides to immunize mice. The relevance of these epitopes to humans was demonstrated, as both were able in vitro to recall specific IFN-gamma and IL10-producing cells from peripheral blood mononuclear cells of HCV infected patients. Such epitopes enlarge the pool of NS3-specific CD8+T cell epitopes available to perform immunomonitoring of HCV infection and to develop vaccines.

Immunogenic HLA-B*0702-Restricted Epitopes Derived from Human Telomerase Reverse Transcriptase That Elicit Antitumor Cytotoxic T-Cell Responses

PURPOSE

The human telomerase reverse transcriptase (hTERT) is considered as a potential target for cancer immunotherapy because it is preferentially expressed in tumor cells. To increase the applicability of hTERT-based immunotherapy, we set out to identify CTL epitopes in hTERT restricted by HLA-B*0702 molecule, a common MHC class I allele.

EXPERIMENTAL DESIGN

HLA-B*0702-restricted peptides from hTERT were selected by using a method of epitope prediction and tested for their immunogenicity in human (in vitro) and HLA-B*0702 transgenic mice (in vivo).

RESULTS

All the six hTERT peptides that were predicted to bind to HLA-B*0702 molecule were found to induce primary human CTL responses in vitro. The peptide-specific CD8+ CTL lines were tested against various hTERT+ tumor cells. Although differences were observed according to the tumor origin, only three CTL lines specific for p277, p342, and p351 peptides exhibited cytotoxicity against tumor cells in a HLA-B*0702-restricted manner. In addition, this cytotoxicity was inhibited by the addition of peptide-loaded cold target cells and indicated that these epitopes are naturally processed and presented on the tumor cells. Further, in vivo studies using humanized HLA-B*0702 transgenic mice showed that all the candidate peptides were able to induce CTL responses after peptide immunization. Furthermore, vaccination with a plasmid DNA encoding full-length hTERT elicited peptide-specific CTL responses, indicating that these epitopes are efficiently processed in vivo.

CONCLUSIONS

Together with previously reported hTERT epitopes, the identification of new CTL epitopes presented by HLA-B*0702 increases the applicability of hTERT-based immunotherapy to treating cancer.

A frameshift polymorphism in P2X5 elicits an allogeneic cytotoxic T lymphocyte response associated with remission of chronic myeloid leukemia

Minor histocompatibility antigens (mHAgs) constitute the targets of the graft-versus-leukemia response after HLA-identical allogeneic stem cell transplantation. Here, we have used genetic linkage analysis to identify a novel mHAg, designated lymphoid-restricted histocompatibility antigen-1 (LRH-1), which is encoded by the P2X5 gene and elicited an allogeneic CTL response in a patient with chronic myeloid leukemia after donor lymphocyte infusion. We demonstrate that immunogenicity for LRH-1 is due to differential protein expression in recipient and donor cells as a consequence of a homozygous frameshift polymorphism in the donor. Tetramer analysis showed that emergence of LRH-1-specific CD8+ cytotoxic T cells in peripheral blood and bone marrow correlated with complete remission of chronic myeloid leukemia. Furthermore, the restricted expression of LRH-1 in hematopoietic cells including leukemic CD34+ progenitor cells provides evidence of a role for LRH-1-specific CD8+ cytotoxic T cells in selective graft-versus-leukemia reactivity in the absence of severe graft-versus-host disease. These findings illustrate that the P2X5-encoded mHAg LRH-1 could be an attractive target for specific immunotherapy to treat hematological malignancies recurring after allogeneic stem cell transplantation.

HLA-A*0201, HLA-A*1101, and HLA-B*0702 transgenic mice recognize numerous poxvirus determinants from a wide variety of viral gene products

In virus models explored in detail in mice, CTL typically focus on a few immunodominant determinants. In this study we use a multipronged approach to understand the diversity of CTL responses to vaccinia virus, a prototypic poxvirus with a genome approximately 20-fold larger than that of the model RNA viruses typically studied in mice. Based on predictive computational algorithms for peptide binding to HLA supertypes, we synthesized a panel of 2889 peptides to begin to create an immunomic map of human CTL responses to poxviruses. Using this panel in conjunction with CTLs from vaccinia virus-infected HLA transgenic mice, we identified 14 HLA-A*0201-, 4 HLA-A*1101-, and 3 HLA-B*0702-restricted CD8(+) T cell determinants distributed over 20 distinct proteins. These peptides were capable of binding one or multiple A2, A3, and B7 supertype molecules with affinities typical of viral determinants. Surprisingly, many of the viral proteins recognized are predicted to be late gene products, in addition to the early intermediate gene products expected. Nearly all of the determinants identified have identical counterparts encoded by modified vaccinia virus Ankara as well as variola virus, the agent of smallpox. These findings have implications for the design of new smallpox vaccines and the understanding of immune responses to large DNA viruses in general.

Investigation of peptide involvement in T cell allorecognition using recombinant HLA class I multimers

Alloreactive T cells are involved in injurious graft rejection and graft-vs-host disease. However, they can also evoke beneficial responses to tumor Ags restricted by foreign MHC molecules. Manipulation of these alloreactivities requires information on the basis of T cell allorecognition. The vigorous T cell response to foreign MHC molecules may arise from peptide-independent recognition of polymorphic residues of foreign MHC molecules or peptide-specific recognition of novel peptides presented by foreign MHC molecules. We investigated CD8+ T cell allorecognition using recombinant HLA class I/peptide complexes. Peptide-specific allorecognition was examined using tetramers of HLA-A*0201 representing five peptides derived from ubiquitously expressed self-proteins that are known to bind endogenously to HLA-A*0201. Distinct subsets of CD8+ T cells specific for each HLA-A*0201/peptide combination were detected within four in vitro-stimulated T cell populations specific for foreign HLA-A*0201. Peptide-independent allorecognition was investigated using artificial Ag-presenting constructs (aAPCs) coated with CD54, CD80, and functional densities of a single HLA-A*0201/peptide combination for four different peptides. None of the four T cell populations specific for foreign HLA-A*0201 were stimulated by the aAPCs, whereas they did produce IFN-gamma upon stimulation with cells naturally expressing HLA-A*0201. Thus, aAPCs did not stimulate putative peptide-independent allorestricted T cells. The results show that these alloreactive populations comprise subsets of T cells, each specific for a self-peptide presented by foreign class I molecules, with no evidence of peptide-independent components.

The variation of the novel allele HLA-B*0739 suggests low alloreactivity when mismatched with HLA-B*0702

We here report the identification of a new HLA-B*07 allele in a male Caucasian. The new allele was initially typed as B*0713 by sequence-specific primed PCR. Because of the infrequence of that allele, a sequencing-based typing was performed to confirm that result. This yielded the detection of the novel allele. It is closest to B*070201, while it differs from B*0713 in 12 positions in exon 2. Compared to B*070201, the new variant is characterized by a non-synonymous nucleotide exchange (C-->T) at nucleotide position 118 of exon 2. Previously, this was considered a constant position, suggesting that it is likely to be caused by a single-point mutation. It results in the amino acid exchange Ala-->Val at position 40 of the mature polypeptide. As this position is located in an outer loop of the HLA molecule, it is highly unlikely to affect peptide binding or T-cell receptor interaction. Thus, the newly found allele should have a low alloreactive potential in case of a mismatch to the most common HLA-B allele B*0702.

Identification of an HLA-B*07 allele variant (B*0740) in the Chinese Han population

A novel HLA-B*07 allele, B*0740, has been identified by sequence-based typing (SBT) in the Chinese Han population. This new allele is identical to B*0705 and B*0706 for exons 2, 3, and 4, except for a single nucleotide at position 605 of codon 202 in exon 3 (AAG-->ATG) leading to an amino acid change from lysine to methionine. SBT was performed following allele separation using the Haploprep method. The serological equivalence of B*0740 to the B7 antigen did not change.

Bone marrow donor routine HLA typing identified a novel B*07 allele, B*0734, confirmed by allele-specific DNA cycle sequencing

In this article, we report the identification of a new human leukocyte antigen-B allele in a sample that was tested in our routine typing for bone marrow donors. This novel allele officially designed B*0734 was found in a female donor of Bavarian Caucasoid origin (Laboratory code 121036). The search for unrelated bone marrow donors was initiated by the Aktion Knochenmarkspende Bayern. In comparison to the common B*070201, B*0734 differs at four nucleotide positions, 412 (G-->A), 539 (G-->T), 559 (G-->A) and 560 (A-->C) causing three amino acid substitutions, at postion 138 Asp-->Asn, at position 180 Arg-->Leu and at position 187 Glu-->Thr.

HLA haplotype A*03-B*07 in hemochromatosis probands with C282Y homozygosity: frequency disparity in men and women and lack of association with severity of iron overload

Before the discovery of HFE, reports suggested that hemochromatosis patients with the ancestral haplotype (or some element thereof) have more severe iron overload than those without the haplotype. We performed univariate and multivariate analyses of the relationships of human leukocyte antigen (HLA)-A*03 and HLA haplotype A*03-B*07 to iron measures (serum iron concentration, transferrin saturation, and serum ferritin concentration at diagnosis and units of phlebotomy to achieve iron depletion) in hemochromatosis probands homozygous for HFE C282Y diagnosed in medical care. Iron overload was defined by demonstration of hepatic iron index of > or =1.9 or removal of > or =2.0 g Fe by therapeutic phlebotomy. We tabulated the phenotype frequencies of HLA-A*03 and the frequencies of common HLA haplotypes A*01-B*08, A*02-B*44, A*03-B*07, and A*03-B*14 in three groups of white adults: (1) 141 hemochromatosis probands with C282Y homozygosity; (2) 195 index cases with IgG subclass deficiency (IgGSD) or common variable immunodeficiency (CVID), disorders typically linked to Ch6p, and (3) 750 control subjects. Among probands, 86 men and 42 women had iron overload. Frequencies of HLA-A and -B alleles in probands did not depart significantly from Hardy-Weinberg equilibrium. The phenotype frequency of A*03 did not differ significantly between men and women in the each of the respective three groups. The frequency of haplotype A*03-B*07 was greater in men than women with hemochromatosis (0.3081 vs. 0.1455; P = 0.0019). The frequency of A*03-B*014 was significantly greater in women than men with hemochromatosis (0.1182 vs. 0.0407, respectively; P = 0.0134). Mean values of most iron measures were not affected by numbers of copies of A*03 or by presence of A*03-B*07 in either men or women in univariate analysis. ANOVA models of sex, age at diagnosis, and all HLA alleles and haplotypes in probands were used to determine effects of these variables on iron measures. ANOVA models revealed that (1) there were no significant predictors for serum iron concentration; (2) B*14 is associated with higher transferrin saturation in women and lower transferrin saturation in men; (3) A*01-B*08 is associated with a trend of higher serum ferritin levels; and (4) A*03-B*14 is associated with exaggeration of the age-associated upward trend in units of phlebotomy to achieve iron depletion. In hemochromatosis probands with HFE C282Y homozygosity, we conclude that (1) disparate frequencies of HLA haplotypes A*03-B*07 and A*03-B*14 occur in men and women and (2) HLA-A*03 and HLA-A*03-B*07 are not independent variables associated with iron overload severity.

CD4 and CD8 T-lymphocyte recognition of prostate specific antigen in granulomatous prostatitis

In order to develop immunotherapies for prostate cancer, many groups are exploring vaccination strategies to induce an immune response against prostate specific antigen (PSA). To determine if T-cell recognition of PSA might be a feature of a naturally occurring human disease, we have studied patients with prostatitis, a poorly understood clinical syndrome of men in which there is evidence that an immune response directed against the prostate may be occurring. We wished to determine if a T-cell response to PSA might be occurring in these patients. We generated long-term T-cell lines from peripheral blood mononuclear cells (PBMC) of one patient with granulomatous prostatitis using purified PSA as an antigen. Several CD4+ and CD8+ TcR alpha/beta+ T-cell lines were selected for PSA reactivity as measured by at least a threefold increase in IFN-gamma secretion in response to PSA presented by irradiated autologous PBMC. CD4 and CD8 T-cell lines recognized PSA in the context of HLA-DRbeta1*1501 and HLA-B*0702, respectively. The specificity and HLA restriction of the lines was confirmed using EBV-B cell lines infected with a recombinant PSA-expressing vaccinia virus and also engineered to express PSA by retroviral transfection. HLA-matched targets infected by control vector as well as HLA-mismatched PSA-expressing targets did not induce the response. The data demonstrate that PSA-specific T cells are present in the PBMC of this patient with granulomatous prostatitis, who may be manifesting naturally the type of immune response directed at the prostate that is the goal of prostate cancer immunotherapy. However, the Class I-restricted epitope has not yet been demonstrated to be expressed on the surface of prostate cancer cells. To our knowledge, this is the first demonstration of HLA-DRB1*1501- or HLA-B*0702-restricted responses to PSA and extends the number of HLA molecules accommodating the use of PSA antigen as a candidate vaccine for prostate cancer immunotherapy.

Genetic contribution of tumor necrosis factor (TNF)-alpha gene promoter (-1031, -863 and -857) and TNF receptor 2 gene polymorphisms in endometriosis susceptibility

PROBLEM

Tumor necrosis factor (TNF)-alpha is a major cytokine involved in inflammatory and immune function. The aim of this study was to investigate whether polymorphisms at positions -1031, -863 and -857 in the TNF gene promoter region (TNFA) and TNF receptor type 2 gene (TNFR2) are responsible in part for genetic susceptibility to endometriosis.

METHODS OF STUDY

TNFA and TNFR2 polymorphisms were determined in 123 patients with endometriosis and 165 fertile healthy women by the polymerase chain reaction (PCR) - preferential homoduplex formation assay and PCR-restriction fragment length polymorphism, respectively.

RESULTS

The frequency of the TNFA-U01 haplotype was increased significantly in patients with endometriosis compared with controls (P = 0.045, OR = 1.45). The TNFA-U01 haplotype was strongly associated with HLA-B*0702. No difference was found in TNFR2 polymorphism between patients and controls.

CONCLUSION

Our results indicated that TNFA promoter polymorphism was associated with susceptibility to endometriosis. However, this association was not independent of HLA-class I polymorphisms.

New HLA-B alleles detected by polymerase chain reaction-sequence-specific oligonucleotide typing: HLA-B*0725, B*0728, and B*3808

Three novel alleles, human leukocyte antigen (HLA)-B*0725, B*0728, and B*3808, were discovered during routine genotyping of samples for the Australian Bone Marrow Donor Registry and Australian Cord Blood Bank. The new alleles contain amino acid changes in the antigen-binding site of the expressed HLA protein, which may alter the antigen-binding properties of the functional protein.

Sustained CD8+ T-cell immune response to a novel immunodominant HLA-B*0702-associated epitope derived from an Epstein–Barr virus helicase-primase-associated protein

Generation of a peptide-based vaccine against persistent viral infections, such as Epstein-Barr virus (EBV), requires identification of immunodominant epitopes recognized by anti-viral cytotoxic T-cells. Using available computer algorithms, we have screened the entire translated EBV genome for potential HLA-B7-binding peptides. The binding to HLA-B7 of 18 selected peptides was assessed by competitive binding assays and was found to correlate with the computer-assigned scores, confirming the predictive value of these algorithms in selection of HLA-B7-associated peptides. Screening of the immune responses to these peptides by ELISpot assays identified a novel immunodominant epitope, termed LPRA, derived from an EBV helicase-primase-associated protein encoded by BBLF2/3. Peptide-specific cells constituted up to 0.8% LPRA-specific CD8+ T-cells in the matured anti-viral response. Cytotoxic and proliferative cytotoxic T lymphocytes (CTL) responses to the LPRA peptide were readily demonstrated ex vivo. In addition, mutational studies of this epitope demonstrated a highly specific recognition by LPRA-specific CD8+ T-cells. Taken together, our data suggest that the novel lytic-phase HLA-B7-associated epitope contains essential features required of a component in an EBV peptide-based vaccine.

HLA-B*0702 transgenic, H-2KbDb double-knockout mice: phenotypical and functional characterization in response to influenza virus

HLA-B*0702 transgenic mice (expressing a chimeric heavy chain with a murine alpha 3 domain: HLA-B7(m alpha 3)) in which the H-2K(b) and H-2D(b) class I-a (Cl I-a(-/-)) genes have been inactivated were compared with H-2K(b)D(b) Cl I-a(+/+) positive controls. Expression of the HLA-B7(m alpha 3) molecules resulted in a 3- to 4-fold increase in peripheral CD8(+) T lymphocyte numbers compared to H-2 Cl I-a(-/-) knockout mice. These cells show a diversified TCR repertoire. Following influenza infection, a significant improvement in HLA-B0702-restricted cytotoxic T lymphocyte (CTL) responses was observed in HLA-B7(m alpha 3), H-2 Cl I-a(-/-) compared to HLA-B7(m alpha 3), H-2 Cl I-a(+/+) mice. The CTL response of infected HLA-B7(m alpha 3), H-2 Cl I-a(-/-) mice was directed against the nucleoprotein (NP) 418-426 epitope in which mutations have accumulated. Whereas all NP 418-426 variant peptides induced a CTL response, cross-reactivity to the variants was affected. These NP mutations could have been selected over time in humans for the virus to escape HLA-B0702-restricted CTL responses since a similar response was seen in humans with, as in mice, altered cross-recognition of the NP 418-426 variants. These animals may prove a suitable model to study HLA-B0702-restricted CTL responses.

Relative dominance of HLA-B*07 restricted CD8+ T-lymphocyte immune responses to human cytomegalovirus pp65 in persons sharing HLA-A*02 and HLA-B*07 alleles

CD8(+) T-cell responses to three human cytomegalovirus (CMV) pp65 epitopes were studied in panels of healthy seropositive HLA-A*02/HLA-B*07 individuals, and HLA-A*02 donors mismatched for HLA-B*07. The majority of the latter had significant responses to a HLA-A*02-restricted epitope within the CMV pp65 antigen. By contrast, the strongest responses to CMV in the first group were to HLA-B*07-restricted epitopes. Similar immunodominance of HLA-B*07 over HLA-A*02 was found in two immunocompromised HIV-infected HLA-A*02/HLA-B*07 patients, and in the reconstituting immune system of three stem cell transplant recipients. In vitro stimulation of peripheral blood mononuclear cells (PBMC) from two immunocompetent HLA-A*02/HLA-B*07 individuals indicated that cytotoxic T lymphocyte (CTL) precursors specific for both HLA-A*02 and HLA-B*07 restricted epitopes were present and could be expanded by stimulation with the cognate peptides. However, if stimulation was performed by antigen presenting cells infected with recombinant vaccinia expressing full-length native pp65, only HLA-B*07 epitope-specific cells were seen. In one patient the HLA-B*07 dominance was partially broken by using recombinant vaccinia expressing ubiquitinated pp65, suggesting that enhanced protein processing can reveal weaker immune responses. Our results indicate that CMV-specific cellular immune responses restricted by HLA-B*07 dominate those restricted by HLA-A*02 in both immunocompetent and immunocompromised individuals. This may have significant consequences for the design of epitope-specific vaccines.

Derivation of HLA-B*0702 transgenic mice: functional CTL repertoire and recognition of human B*0702-restricted CTL epitopes

Transgenic mice expressing chimeric human leukocyte antigen (HLA)-B*0702 and murine H-2K(b) class I molecules were evaluated as a model system to study the immunogenicity of human cytotoxic T lymphocyte epitopes. Immunization of these mice with six known HLA-B*0702-restricted cytotoxic T lymphocyte epitopes emulsified in incomplete Freund's adjuvant induced significant immune responses specific for all six epitopes. A comparison of the immune responses between HLA-B*0702/K(b) and HLA-A*0201/K(b) transgenic mice demonstrated that the HLA-B*0702/K(b) mice possess a T-cell receptor repertoire capable of recognizing human B*0702 epitopes. However, the magnitude of B*0702-specific responses induced in B*0702/K(b) mice were approximately tenfold lower than A*0201-specific responses induced in HLA-A*0201/K(b) transgenic mice. A panel of 24 B*0702 motif-bearing peptides was used to examine the relationship between immunogenicity and HLA-B*0702 binding capacity. All seven peptides with high binding affinities of 50% inhibitory concentration < or =50 NM (IC(50) 50 nM or less) were immunogenic. Similarly, 75% (9 of 12) of the intermediate binders (IC(50) nM of 50-500) were also immunogenic. Finally, only two of five peptides with binding capacity > 500 nM were found to have marginal immunogenicity, whereas the other three were completely negative. HLA-B*0702/K(b) transgenic mice were found to induce B*0702-specific responses after immunization with whole DNA genes or minigenes, suggesting that, at least to some degree, B*0702 epitopes were generated as a result of natural in vivo processing and presentation.

T cell responses to an HLA-B*07-restricted epitope on the dengue NS3 protein correlate with disease severity

Dengue hemorrhagic fever (DHF), the severe manifestation of dengue virus (DV) infection characterized by plasma leakage, is more common in secondary DV infections in previously infected individuals and is associated with high levels of immune activation. To determine the Ag specificity of this immune response, we studied the response to an HLA-B*07-restricted T cell epitope, residues 221-232 of the DV NS3 protein, in 10 HLA-B*07(+) Thai children who were studied during and after acute DV infections. Peptide-specific T cells were detected in 9 of 10 subjects. The frequency of peptide-specific T cells was higher in subjects who had experienced DHF than in those who had experienced DF. We also detected peptide-specific T cells in PBMC obtained at the time of the acute DV infection in 2 of 5 subjects. These data suggest that the NS3 (221-232) epitope is an important target of CD8(+) T cells in secondary DV infection and that the activation and expansion of DV-specific T cells is greater in subjects with DHF than in those with dengue fever. These findings support the hypothesis that activation of DV-specific CD8(+) T cells plays an important role in the pathogenesis of DHF.

Identification of a novel HLA-B*07 allele--HLA-B*0726

We describe here, the identification of a novel HLA-B*07 allele named HLA-B*0726. This allele was found in a Caucasian individual serologically typed as HLA-B7, B35. Novel DNA probe patterns for the HLA-B*07 allele were found using HLA-B specific reverse sequence-specific oligonucleotide probe (SSOP) and sequence-specific primer (SSP) typing. DNA sequencing demonstrated the presence of a new HLA-B*07 sequence variant encoding a single nucleotide substitution from a G to a T at nucleotide 539 in exon 3. This results in an amino acid substitution from arginine to leucine at residue 156 in exon 3.

Identification of HLA-B*0722

A novel polymorphism was identified in a B*07 allele. B*0722 possesses a unique nucleotide substitution at nucleotide 481. This polymorphism encodes an amino acid difference from aspartic acid in B*07021 to asparagine in B*0722. The functional significance of this polymorphism on peptide binding and/or T-cell recognition is unknown.

HLA-B*07 allele frequencies and haplotypic associations in Koreans

We have investigated the frequencies of HLA-B*07 alleles and their haplotypic associations with HLA-A, -C and -DRB1 loci in 489 healthy unrelated Koreans, including 214 parents from 107 families. All of the 45 samples (9.2%) typed as B7 by serology were analyzed for B*07 alleles using polymerase chain reaction (PCR)-single strand conformation polymorphism (SSCP) method. Two different B*07 alleles were detected: B*0702 (allele frequency 0.041) and B*0705 (0.005). Two characteristic haplotypes showing strong linkage disequilibrium in Koreans were A*2402-Cw*07-B*0702-DRB1*0101 (haplotype frequency 0.028) and A*2901-B*0705-DRB1*0803 (0.005). The characteristic haplotype A*2901-B*0705-DRB1*0803, found in 100% (5/5) of B*0705-positive individuals, has not been previously described in other ethnic groups. HLA-B7 alleles comprise distinctive extended haplotypes in the Korean population. The probability of HLA-B7 allele mismatches among ABDR-matched unrelated donor-recipient pairs is expected to be low in Koreans.

Characterisation of a new HLA-B allele, HLA-B*0720, identified in the Cuban population

The HLA class I genes display significant levels of polymorphism, which is principally due to hypervariable regions located in the second and third exons. To date, 286 HLA-B alleles have been identified and characterised. We describe a new HLA-B*07 allele present in a Cuban Caucasoid individual, which has been officially named HLA-B*0720.

Human memory CTL response specific for influenza A virus is broad and multispecific

Class I restricted cytotoxic T-lymphocyte (CTL) responses are thought to be focused against few immunodominant epitopes. In humans, an often quoted example of such narrow focus is the influenza A (FLU) matrix 58-66 specific memory CTL activity, detectable in HLA-A2 individuals as a result of natural infection. Herein, we analyzed the repertoire of memory, FLU-specific CTLs in A2 and A11 positive individuals. Eighteen A2.1 binding peptides, derived from the FLU-Puerto Rico/8/34 (PR8) isolate, elicited CTL activity in A2. 1/Kb transgenic mice upon direct immunization. These peptides were also tested for their capacity to recall memory CTL responses from peripheral blood mononuclear cells (PBMC) of human A2.1 donors. Besides the known dominant M1.58 peptide, 5 new epitopes (PA.46, PA. 225, PB1.413, NA.75 and M1.59) were identified. Similarly, eleven, A11-binding, FLU-PR8 peptides, which were immunogenic in HLA-A11/Kb transgenic mice, were assayed for induction of recall CTL responses using peripheral blood lymphocytes from a cohort of A11-positive donors. Eight different peptides (NP.188, NP.342, HA.63(,) HA.149, HA.450, M1.13, M1.178, and M2.70) induced memory CTL activity. Several of these peptides were found to be highly conserved amongst different FLU isolates, and also capable of binding multiple A2 and A11 supertype molecules. Finally, 37 HLA-B7 binding peptides were also identified. In conclusion, a previously unappreciated breadth of FLU-specific, memory CTL responses in humans was revealed. The relevance of these findings to the design of multiepitope vaccines is discussed.

Clinical implications of the new biology in the development of melanoma vaccines

There has been a resurgence in clinical research of vaccine therapies, particularly for the treatment of melanoma. The renewed interest in this field is attributable to an increased understanding regarding the immune response to tumors and the immunobiology of melanoma. Molecular biology techniques have enabled investigators to develop genetically engineered tumor vaccines that are intended to favor the type 1 immune response over the type 2 response. Melanoma-associated antigens have been characterized at the molecular level and are currently being investigated in clinical trials. Dendritic cell biology has also provided a potent method to present antigens to the host for immunization. Lastly, vaccines are being explored as a method to generate immune T-cells for adoptive immunotherapy. These new areas of clinical investigation will be reviewed in the context of the historical developments that have laid the foundations of this field.

Association between longevity and allelic forms of human leukocyte antigens (HLA): population study of aged Italian human subjects

Several arguments support the idea of a link between longevity and heredity, both in humans and in experimental animals. We have therefore investigated the possibility of an association between the human leukocyte antigens (HLA) and longevity in two groups of Italian subjects: 108 healthy subjects over 85 years old, and 749 healthy blood donors (controls). Only four antigens showed a higher frequency in the elder group: HLA-A31(19), B7, Cw7 and DQ1. These findings suggest an involvement of HLA antigens in human longevity, but the real biological meaning of these results is still unclear.

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.

Familial aggregation of undifferentiated spondyloarthropathy associated with HLA-B7

OBJECTIVE

To report multiple cases of recurrent seronegative arthropathy, enthesopathy, or both, occurring in a single family in the absence of the HLA-B27 tissue type, coexistent psoriasis or inflammatory bowel disease.

METHODS

Three generations of one family together with their general practitioners completed a standard questionnaire. All subjects with a positive questionnaire and two randomly chosen subjects with negative questionnaires were then examined by a single observer. HLA tissue typing and standard sacroiliac radiographs were performed.

RESULTS

Seven of 12 family members with a positive questionnaire had early onset oligo- or polyarthritis, enthesitis, or both, and fulfilled established criteria for spondyloarthropathy, although none had radiological evidence of sacroiliitis. The mean age at first symptom in this group was 22 years with only one individual having the first symptom over the age of 30 years. All subjects were rheumatoid factor negative. Histocompatibility studies showed a strong association with the HLA-B7 antigen.

CONCLUSIONS

The observations provide further support for the existence of 'undifferentiated' spondyloarthropathy and suggest that this can be associated with genetic factors other than HLA-B27.

Myasthenia gravis after allogeneic bone marrow transplantation

A 37-year-old Japanese man with chronic myeloid leukemia (CML) developed myasthenia gravis 29 months after bone marrow transplantation (BMT) from an HLA one locus-mismatched brother. Proximal muscle weakness and bilateral ptosis occurred along with the exacerbation of chronic GVHD shortly after sudden cessation of cyclosporine (CYA) and prednisolone. The diagnosis of myasthenia gravis was made based on clinical symptoms and elevation of an anti-acetylcholine receptor antibody titer and all symptoms related to myasthenia gravis promptly diminished with the start of treatment for chronic GVHD. In most previously reported cases, the underlying disease was aplastic anemia (6 of 7 cases) and donors were of the opposite sex (6 of 7 cases). The haplotypes HLA B7 (3 of 5 cases), B35 (3 of 5 cases), and DR2 (3 of 3 cases) were common. All cases suffered from chronic GVHD. The present case had only chronic GVHD and HLA B7 as a background for myasthenia gravis after BMT. The abrupt cessation of immunosuppressive therapy may also be related to the development of myasthenia gravis after BMT.

[Genetic hemochromatosis and mixed gonadal dysgenesis]

We report a case of association between genetic haemochromatosis and mixed gonadal dysgenesis. To our knowledge, this case is the first reported in the literature. We discuss the mechanisms of hypogonadism observed in this patient.

Delineation of determinants on HLA-B7 and HLA-B27 that are necessary for cytolytic T cell recognition by using inter- and intra-domain recombinants

We have used bulk culture HLA-B7 and HLA-B27 specific CTL lines derived from 11 donors, and a series of rHLA-B7/HLA-B27 genes transfected into and expressed on the surface of the murine cell P815, to determine the amino acid residues on these HLA class I molecules that are critical for allospecific CTL recognition. The results obtained indicate that for four of six HLA-B7-specific CTL lines the alpha-1 domain for CTL recognition. Furthermore, we found that residues 77 and/or 80 had a critical effect on recognition for all of the CTL lines tested. The region 97-156 in the alpha-2 domain was also important for some of these CTL lines. Furthermore, by using five bulk culture HLA-B27-specific CTL lines we were able to show that residues 77 and/or 80 and residue 152 are also essential for recognition of HLA-B27 by HLA-B27-specific CTL. The strong influence exerted by these residues is discussed in terms of the three-dimensional structure of class I molecules. Finally, a selection was regularly observed in the bulk cultures such that the CTL that were preferentially influenced by either the alpha-1 or the alpha-2 domain were lost after 4 to 7 wk of culture resulting in CTL cell lines which were extremely sensitive to sequence modifications of HLA-B7 or HLA-B27. The possible reasons for this selection, which we have previously observed with both anti-HLA-A2 and anti-HLA-A3 cell lines and is therefore not unique to HLA-B7 or HLA-B27, are discussed.

Multiple enhancer-like sequences in the HLA-B7 gene

Enhancer-like sequences have previously been identified in the promoter region of the mouse major histocompatibility complex (MHC) class I genes. We have screened for such sequences in and around a human MHC class I gene, HLA-B7. Various restriction fragments of the B7 gene were assayed for their ability to enhance transcription of a bacterial chloramphenicol acetyltransferase gene from a simian virus 40 promoter in transiently transfected mouse LTA cells. Our results demonstrate that enhancer activity is located in introns 3 and 5 as well as 5' to the transcription initiation site. RNase protection experiments corroborate the results. Preliminary experiments indicate that B7 enhancers are active in various cell types. The role of these enhancers in B7 gene expression is not known at present. We speculate that the position of the enhancer elements may be related to the occurrence of Hpa II tiny fragment islands.

Cytotoxic T cell responses in HLA-A2.1 transgenic mice. Recognition of HLA alloantigens and utilization of HLA-A2.1 as a restriction element

Previous studies have indicated that the frequency of murine CTL precursors (CTLp) for human class I molecules is one to two orders of magnitude lower than that for murine class I alloantigens, and that this is due to species-specific structural differences between these molecules. Transgenic mice expressing the human class I MHC Ag HLA-A2.1 were used to examine changes in the frequency of class I HLA-specific precursors after T cell differentiation in an HLA-A2.1 positive environment. The HLA-A2.1 gene product was expressed at levels comparable to those of the endogenous H-2Db molecule in thymus, bone marrow, and spleen. By limiting dilution analysis, it was observed that the frequencies of CTLp in transgenic mice responding to the human alloantigens HLA-B7 or HLA-A2.2 were comparable to or lower than those in normal C57BL/6 mice, regardless of whether the Ag was presented on human or murine cells. Thus, expression of a human class I molecule in these animals did not result in an expansion of the number of CTLp specific for other human class I Ag. In addition, the frequency of HLA-A2.1-restricted, influenza specific CTLp was substantially lower than the frequency of H-2b restricted CTLp, indicating a poor utilization of HLA-A2.1 as a restricting element. Finally, the frequencies of CTLp for HLA-A2.1 expressed on syngeneic murine tumor cells were decreased significantly. Thus, expression of HLA-A2.1 in these animals appeared to induced tolerance to this Ag. Interestingly, however, these mice were not tolerant to the HLA-A2.1 molecule expressed on human cells. This indicates that the HLA-A2.1 associated epitopes expressed on murine and human cells differ and suggests that, under these circumstances, HLA-A2.1 acts as a restricting element for human nominal Ag. These results are discussed in the context of current models of T cell repertoire development.

[HLA studies and histochemical detection of liver iron in porphyria cutanea tarda]

With regard to disturbances of the iron metabolism, porphyria cutanea tarda (PCT) is most frequently accompanied by liver siderosis. In 74 out of 88 patients suffering from PCT (84%), we found histochemical evidence of liver siderosis. These patients showed a significantly higher incidence of HLA A3--which has been proved to be associated with hemochromatosis--than those without liver siderosis (39.2% vs. 7.1%). With part of the PCT patients, disorders of the iron metabolism related to the HLA system (A3) might contribute to the manifestation of the disease. We discuss PCT as the result of the combined action of several predisposing genetic markers and exogenic factors.

IFN-mediated differential regulation of the expression of HLA-B7 and HLA-A3 class I genes

The regulation by IFN of the expression of HLA-B7 and HLA-A3 class I molecules was studied in Jurkat human T lymphoma cells, HHK EBV-transformed human B lymphocytes, and murine HLA-B7 HLA-A3 co-transfected L fibroblasts. Jurkat cells express constitutively low level of HLA class I molecules and treatment with human IFN resulted in preferential increase of the expression of HLA-B7 molecules, the expression of the HLA-A3 molecules being relatively unchanged. Similar treatment of HHK cells, which express constitutively large amount of HLA class I molecules, resulted in a marginal increase of the expression of both HLA-B7 and HLA-A3 molecules. HLA-B7 HLA-A3 co-transfected L cells express relatively low level of HLA class I molecules, expression of both however was significantly increased after treatment with murine INF-alpha, the augmentation being more accentuated for HLA-B7 molecules. In all cases, variations of cell surface expression were related to parallel modifications of the level of HLA-B7 and HLA-A3 RNA transcripts. Important nucleotide differences exist between the IFN consensus sequences associated with the HLA-B7 and HLA-A3 class I genes. Using oligonucleotides corresponding to these sequences two patterns of retarded bands were observed by the gel mobility shift assay, suggesting that the IFN-mediated differential regulation of the expression of the HLA-B7 and HLA-A3 genes could be due to different nuclear regulatory factors.

Tissue-specific and cell surface expression of human major histocompatibility complex class I heavy (HLA-B7) and light (beta 2-microglobulin) chain genes in transgenic mice

We introduced the human genes HLA-B7 and B2M encoding the heavy (HLA-B7) and light [beta 2-microglobulin (beta 2m)] chains of a human major histocompatibility complex class I antigen into separate lines of transgenic mice. The tissue-specific pattern of HLA-B7 RNA expression was similar to that of endogenous class I H-2 genes, although the HLA-B7 gene was about 10-fold underexpressed in liver. Identical patterns of RNA expression were detected whether the HLA-B7 gene contained 12 or 0.66 kilobase(s) (kb) of 5' flanking sequence. The level of expression was copy number dependent and as efficient as that of H-2 genes; gamma interferon enhanced HLA-B7 RNA expression in parallel to that of H-2. In addition to the mechanism(s) responsible for gamma interferon-enhanced expression, there must be at least one other tissue-specific mechanism controlling the constitutive levels of class I RNA. Tissue-specific human beta 2m RNA expression was similar to that of mouse beta 2m, including high-level expression in liver. Cell surface HLA-B7 increased 10- to 17-fold on T cells and on a subset of thymocytes from HLA-B7/B2M doubly transgenic mice compared to HLA-B7 singly transgenic mice. The pattern of expression of HLA-B7 on thymocytes resembled that of H-2K as opposed to H-2D. These results confirm that coexpression of both human chains is required for efficient surface expression and that HLA-B7 may share a regulatory mechanism with H-2K, which distinguishes it from H-2D.

Genetic susceptibility to multiple sclerosis. A co-twin study of a nationwide series

The problems of differentiation between environmental and genetic influences on the development of multiple sclerosis are well known. Twin studies may provide valuable information on this question. However, most published twin series are selected and no through clinical twin studies based on epidemiologic series have been carried out. In this study, all available same-sex twin pairs with clinically definite multiple sclerosis derived from the Finnish Twin Cohort of 15815 pairs were studied by clinical evaluation, magnetic resonance imaging, and visual and auditory evoked responses. The mean length of follow-up of the pairs after the onset of symptoms of multiple sclerosis was 20 years. Two of the seven monozygotic pairs were concordant; one was definitely so, and in the other, the co-twin of the index case had, in addition to clinical findings, white matter changes suggestive of multiple sclerosis in magnetic resonance imaging and abnormal visual evoked responses. All six dizygotic pairs were discordant. The frequency of the HLA antigen DR2 in probands (69%) was significantly increased, but the distribution among the healthy subjects and patients showed nonsignificant differences. The results indicate a genetic influence on the susceptibility to multiple sclerosis, although still unknown genetic determinants are possible involved.