Role of tropomyosin as a cross-reacting allergen in sensitization to cockroach in patients from Martinique (French Caribbean island) with a respiratory allergy to mite and a food allergy to crab and shrimp

BACKGROUND

Tropomyosin has been described as cross-reacting allergen between mite, cockroach and shrimp.

METHODS

In 13 patients with asthma and/or rhinitis sensitized to mite and/or German cockroach and presenting urticaria, oral allergy syndrome or angio-edema upon eating shrimp and/or crab, we measured specific IgE to mite, cockroach, crab and shrimp tropomyosin.

RESULTS

Ten patients had specific IgE to tropomyosin from mite, 8 from shrimp, 6 from crab and 5 from cockroach. AST inhibition tests indicated that mite allergen is a primary sensitizer and is cross-reacting with shrimp, crab and cockroach allergens.

CONCLUSION

Tropomyosin could be the cross-reacting allergen relevant for clinical symptoms to mite, cockroach, shrimp and crab.

Impact factors on intraocular pressure measurements in healthy subjects

AIM

To evaluate whether intraocular pressure (IOP) calculation by applanation tonometry is determined more essentially by the subject's neck position or by neck constriction.

METHODS

23 right eyes of 23 healthy subjects (12 male, 11 female) were included. IOP was measured by applanation tonometry with the TonoPen on sitting participants under four different conditions: with open collar upright (A) or with the head in the headrest of a slit lamp (B), with a tight necktie upright (C) or in slit lamp position (D). All measurements with neck constriction were performed 3 minutes after placing the necktie.

RESULTS

Mean IOP was 16.9 (SD 2.3) mm Hg (range 11-21 mm Hg) (A), 18.1 (SD 2.2) mm Hg (range 14-22 mm Hg) (B), 17.9 (SD 2.9) mm Hg (range 12-25 mm Hg) (C) and 18.7 (SD 2.7) mm Hg (range 13-24 mm Hg) (D). Mean IOP increased by 1.3 (SD 2.6) mm Hg (p = 0.028, paired t test, range +0.2 to +2.4 mm Hg) if subjects changed position from A to B. There was no statistically significant difference between measurements with or without neck constriction.

CONCLUSION

Applanation tonometry may be inaccurate if performed in slit lamp position. In contrast, tight neckties do not significantly affect IOP evaluation in healthy subjects.

Efficacy of birch-pollen immunotherapy on cross-reactive food allergy confirmed by skin tests and double-blind food challenges

BACKGROUND

The effect of birch-pollen immunotherapy (IT) on cross-reactive food allergies is controversial.

OBJECTIVE

The aim of this study was to investigate the effect of birch-pollen IT on apple allergy and to evaluate recombinant allergens and double-blind placebo-controlled food challenges (DBPCFCs) as monitoring tools.

METHODS

Twenty-five adult birch-pollen- and apple-allergic patients were randomly divided into two groups, either receiving birch-pollen IT or symptomatic drugs only. IgE and IgG4 antibodies against birch pollen, apple, natural Bet v 1 and Mal d 1 were measured. In addition, skin prick tests (SPT) were performed using recombinant Bet v 1 (rBet v 1) and Mal d 1 (rMal d 1). Clinical outcome was evaluated by DBPCFC. CD4(+)CD25(+) regulatory T cells (Tregs) were isolated from peripheral blood and tested in functional assays.

RESULTS

Birch-pollen IT resulted in a significant decrease of SPT reactivity for rBet v 1 (30-fold) and rMal d 1 (10-fold) already after 3 months. IgG4 antibodies were potently induced against Bet v 1, displaying cross-reactivity to Mal d 1. Visual analogue scale scores decreased >10-fold in 9/13 patients of the IT group, with three patients converting to negative. In the control group, no decrease was observed. Birch-pollen IT did not lead to detectable changes in the number or function of the CD4(+)CD25(+) Tregs.

CONCLUSIONS

This trial supports the claims that birch-pollen IT also decreases allergy to foods containing Bet v 1-homologous allergens. Recombinant allergens and DBPCFCs have proven to be useful tools for monitoring the effect of birch-pollen IT on linked food allergies.

The role of different histocompatibility testing methods for selection of related and unrelated bone marrow donors

Bone marrow transplantation has become the treatment of choice for many hematological malignancies. Approximately 30% of the patients lack an HLA-identical sibling donor, for them alternative donors have to be found. The chances of finding an unrelated donor can be estimated by consulting the Bone Marrow Donors Worldwide file and grouping the patients according to whether they have frequent or rare haplotypes. If the HLA-ABDR split antigens are taken into account, for less than 25% of the patients identical donors can be identified. In order to select the best matched donor for a patient, sensitive HLA typing techniques should be employed including DNA typing techniques, but for optimal selection of a suitable donor one should not only study genetics but also determine the immunological repertoire recognizing the histocompatibility differences between donor and recipient. Several promising cellular techniques such as the HTLp and CTLp test have recently become available and should also be used to select the best donor.

Monoclonal antibodies against the human mannose receptor as a specific marker in flow cytometry and immunohistochemistry for macrophages

Recently we developed mouse monoclonal antibodies (mAb) against the isolated human 175-kDa mannose receptor. In the present study we tested whether these mAb are suitable for the detection of the mannose receptor on cultured macrophages using flow cytometry and on cells in human tissues using immunohistochemistry. Human monocytes did not react with the mAb in flow cytometry. Mannose receptor expression became detectable on monocytes cultured for 3 days (macrophages), and was maximal from 4 days onward. The mannose receptor was up-regulated on dexamethasone-treated (immunosuppressed) macrophages, and down-regulated on lipopolysaccharide-treated (activated) macrophages. Immunohistochemically the staining pattern of our mAb was compared with the marker of monocytes/macrophages KP1. In a bone marrow smear, only macrophages were stained with our mAb, whereas all myeloid cells were stained with KP1. In the thymus and lymph node, mannose receptor-positive branched cells (macrophages and dendritic cells) were detected in connective tissue, thymus cortex (not medulla), and in the T cell area (not the B cell area) of lymph nodes, whereas KP1 stained branched cells in all areas. It was concluded that the mAb are useful tools in flow cytometry and immunohistochemistry for the specific detection of cells expressing mannose receptor.

Bone Marrow Donors Worldwide: a successful exercise in international cooperation

Bone marrow transplantation using unrelated donors has become a clinical reality but a large number of challenges remain. One of the most important and a crucial one is locating a suitable donor. To cope with this very large registries have been formed but each of these lacks donors with phenotypes which occur in other registries. To facilitate the search process a collation system designated Bone Marrow Donors Worldwide (BMDW) was started. Several times a year it collects the phenotypes of all donors from all participating registries on a worldwide basis. The data are sorted by phenotype number of the broad antigens; the splits are specified immediately after the broad phenotypes. Here the experience with the first 11 editions is summarized. Although there is a steady increase in the numbers of donors and phenotypes included in BMDW, < 1% of the theoretically possible HLA-A, -B, -DR split phenotypes are so far represented. Furthermore, 70% of these phenotypes are unique, i.e. they occur in one donor only. As a result 30% of the donors have a phenotype which occurs in one registry only. Of 49 Europdonor donors who donated bone marrow, 8 (16%) had a phenotype which did not occur in any of the other registries. Because BMDW indicates in which registry a potential donor can be located, it can reduce search time by 75%. We conclude that the use of BMDW is the fastest and most cost-effective way to locate donors with rare phenotypes, whether or not they are of Caucasoid origin.

Enzymatic preparation of 1,6-anhydro-muropeptides by immobilized murein hydrolases from Escherichia coli fused to staphylococcal protein A

In order to produce biologically active 1,6-anhydro-muropeptides in large amounts by enzymatic degradation of isolated bacterial murein polymer highly specific periplasmic murein-metabolizing enzymes from Escherichia coli are made available. The genes slt, dacB, and mepA, encoding the soluble lytic transglycosylase (Slt), the penicillin-sensitive DD-endopeptidase (PBP4), and the penicillin-insensitive murein endopeptidase A (MepA), were independently fused to the N-terminal encoding sequence of staphylococcal protein A (SpA) under control of the temperature-inducible phage lambda pR promoter. The SpA fusion proteins were stably over-produced at high levels in E. coli upon temperature induction at 42 degrees C and account for 3% (5 mg SpASlt/l culture), 3% (5 mg SpAPBP4/l culture), and 0.3% (0.5 mg SpAMepA/l culture) of total protein. The SpA fusion proteins, immobilized on IgG Sepharose, are proteolytically sensitive, in vitro, resulting in complete degradation of the SpA portion of the fusion proteins and release of the murein hydrolases in intact and enzymatically active form into the supernatant. Proteolytic degradation could be prevented by p-hydroxymercuribenzoic acid (PHMB) or ethylenediaminetetraacetate (EDTA) suggesting the involvement of the periplasmic protease Pi from E. coli. The immobilized fusion proteins were enzymatically active and could be used for the batch production of biologically active 1,6-anhydro-muropeptides, which were successively separated on HPLC. Isolated murein polymer was degraded quantitatively to monomeric 1,6-anhydro-muropeptides when immunoglobulin G (IgG)-SpASlt was used in combination with IgG-SpAMepA. A combination of IgG-SpASlt with IgG-SpAPBP4 left the 1,6-anhydro-dimers and oligomers being cross-linked via an LD-peptide bond (m-DAP-m-DAP) uncleaved.

N-myc expression switched off and class I human leukocyte antigen expression switched on after somatic cell fusion of neuroblastoma cells

Neuroblastomas often show amplification and high expression of the N-myc oncogene. N-myc expression could be explained as a consequence of gene amplification, but an alternative possibility is that expression primarily results from the inactivation or loss of some factor that normally represses the N-myc gene. To test this idea, we fused N-myc-overexpressing neuroblastoma cell lines with lines that do not express N-myc. In the resulting hybrids, N-myc expression turned out to be switched off, although amplified N-myc copies were still present. This suggests that N-myc overexpression in neuroblastomas results, at least in part, from the inactivation of a suppressor gene that is present in normal cells. In rat neuroblastomas, it has been found that N-myc can switch off class I major histocompatibility complex (MHC) expression. Therefore, we analyzed in our hybrid cells whether suppression of N-myc results in reexpression of human class I MHC genes. Because this was found to be the case, the picture emerges of a hierarchic pathway that connects a putative tumor-suppressor gene with the expression of N-myc and consequently of class I MHC, thus affecting the potential immunogenic properties of neuroblastomas.

Trial and error in producing ankylosing-spondylitis-selective antisera according to Andrew Geczy

Geczy found that rabbit sera raised against Klebsiella strain K43 cross-reacted with the cells from HLA-B27 positive patients with ankylosing spondylitis (AS). Other laboratories failed to reproduce these results. After a series of unsuccessful attempts, however, we managed to prepare one selective antiserum, using E. coli, isolated from a Dutch Bechterew patient, in offspring of rabbits Geczy sent us. Ever since we obtained irreproducible results only. This paper reports about the many attempts we have made to produce a discriminating antiserum for use in a combined vital stain and dye-exclusion assay.

Suppression of class I human histocompatibility leukocyte antigen by c-myc is locus specific

The c-myc oncogene downregulates class I HLA expression in human melanoma. The major class I HLA antigens are encoded by three loci, A, B, and C, and we investigated whether these loci are suppressed equally by c-myc. In three melanoma cell lines with high c-myc expression, we analyzed mRNA, protein, and cell surface expression of the class I HLA antigens. Whereas the HLA-B locus expression was found to be strongly reduced, the HLA-A locus was expressed normally. Analysis of c-myc-transfected clones of two melanoma cell lines confirmed that c-myc preferentially suppresses the class I HLA-B locus. Immunohistochemical analysis of fresh melanoma lesions also showed that in the tumors the HLA-A loci are expressed normally, while on the majority of tumor cells no HLA-B antigen expression was found. This downregulation may have consequences for the recognition of malignant cells by tumor-infiltrating lymphocytes. Our results predict that HLA-B-restricted cytotoxic T cells will be unable to kill high c-myc-expressing melanoma cells.

Hyperimmunized patients do not need to wait for an HLA identical donor

Hyperimmunized patients tend to accumulate on renal transplant waiting lists because their high level of sensitization leads to positive crossmatches with almost all potential organ donors. The origins of sensitization and the different efforts made to find cross-match negative donors for these patients are discussed. Special emphasis is given to a local strategy based on the determination of HLA-A and -B mismatches, against which the patient did not form allo-antibodies, the so-called acceptable mismatches. Kidney donor selection is based on compatibility with the patient's own HLA-antigens in combination with the acceptable HLA-A and -B antigens, and can be operated from a central organ-sharing office. The acceptable HLA mismatches are often identical with or include the non-inherited HLA class I antigens of the mother (non-inherited maternal antigens: NIMA).

In vivo effects of combination treatment with recombinant interferon-gamma and -alpha in metastatic melanoma

The toxicity and therapeutic efficacy of the combination of recombinant interferon gamma (rIFN-gamma) and alpha (rIFN-alpha) was investigated in 15 patients with metastatic melanoma. Patients were treated with an escalating dose of rIFN-gamma and a fixed dose of rIFN-alpha administered s.c. 3 times a week. The maximum dose was well tolerated. The median survival time of the patients was 7 months; no clinical remissions were observed. In the majority of cases, expression of HLA class-I and -II antigens on the patients' peripheral blood lymphocytes and monocytes increased markedly during treatment. An increase in HLA-DR expression of peripheral blood T lymphocytes was correlated with a longer survival time. This suggests that activation of T lymphocytes may have a favourable influence on the course of metastatic disease. The in vitro anti-proliferative activity of IFNs on melanoma cell lines isolated from melanoma metastases during treatment of 3 patients was determined. In contrast to the lack of in vivo anti-tumour effect in patients, both rIFN-gamma and rIFN-alpha inhibited DNA synthesis of these melanoma cell lines in vitro, combined IFNs acting synergistically. Anti-proliferative activity observed in vitro occurred at IFN concentrations below the peak serum levels achieved in vivo.

Rabbit antisera to enterobacteriaceae isolated from HLA-B27 positive patients with ankylosing spondylitis (AS) are lytic for the mononuclear cells of AS patients

Vaccines prepared from Gram-negative bacteria isolated from the stools of HLA-B27 positive AS patients were used to immunize rabbits. Three of the sera obtained were lytic in vitro for the mononuclear cells of HLA-B27 positive AS patients. One of these sera discriminated between AS patients and healthy HLA-B27 positive individuals. Cytolysis was determined in an automated, non-radioactive assay based on the release of carboxyfluorescein diacetate and the incorporation of propidium iodide.

Blind confirmation in Leiden of Geczy factor on the cells of Dutch patients with ankylosing spondylitis

A follow-up blind study, of the ability of "cross-reactive" antisera to distinguish between the cells of Dutch patients with ankylosing spondylitis (AS) and normal controls, was performed in Leiden. Of the 45 cell samples tested, 29 were fresh peripheral blood mononuclear (PBM) cells while 15 were cryopreserved PBM. No false positives but one false negative was identified among the 45 samples, and the "negative" was confirmed after the recoded cryopreserved cells from this patient were retested. It is concluded that the "cross-reactive" antisera raised in Sydney give good discrimination between patients and normals. Factors affecting the success of the 51Cr-release cytotoxicity assay, and possible reasons for the failure of others to confirm these observations, are briefly discussed.

TCA: a polymorphic genetic marker in leukemias and melanoma cell lines

TCA (T Cell system A) is a di-allelic system of HLA-like antigens encoded by genes located about 15 cM telomeric to HLA-A. In normal individuals, TCA antigens are only expressed on a subpopulation of T cells, the TG lymphocytes. We now report on the expression of TCA on leukemias and other malignancies. An increased proportion of cells carrying the TCA phenotype was encountered in testing peripheral blood lymphocytes from patients with acute lymphoblastic T-cell leukemia (T-ALL), acute myeloid leukemia (AML), and chronic myeloid leukemia (CML). In contrast, patients with B-cell malignancies such as chronic lymphatic leukemia (CLL) and hairy cell leukemia (HCL) or non-T/non-B common acute lymphoblastic leukemia (common ALL) had normal proportions of TCA-positive lymphocytes. Quantitatively different levels of TCA expression are found on some melanoma cell lines and others are TCA negative. These variations are independent of the expression of HLA Class I antigens by the same cells. The expression of TCA antigens by malignant nonlymphoid cells suggests that this system may code for differentiation markers, important in the biology of neoplastic transformation.

Recognition of polymorphic monocyte antigens

Sera from multiparous women and renal transplant recipients were screened for the presence of anti-monocyte antibodies. Reactions caused by anti-HLA antibodies were excluded by using panel cells that were HLA-compatible with the antibody producers. Six sera with monocyte-specific antibodies were identified, and at least two monocyte-specific (probably allelic) antigens could be recognized. The perspective of the clinical significance of typing for monocyte-specific antigens is discussed.

Two different T-cell systems in humans, one of which is probably equivalent to Qa or Tla in mice

Two different alloantigenic systems, expressed mainly on TG and TM lymphocytes and called TCA and TCB, respectively, are described. Alloantisera from parous women are absorbed with Epstein-Barr virus-transformed B cell lines from the husband of the serum producer to remove all anti HLA-A,B,C and DR antibodies. The absorbed sera are tested against a random panel and against lymphocytes from families. Family studies indicate that the TCA system might be encoded by a gene linked to HLA and located on the telomeric side of HLA-A. The total lod scores for the material of 15 informative families is +3.301 at a recombination fraction of 15%. Furthermore we can show that the TCA molecule is associated with beta 2-microglobulin by blocking with turkey anti-beta 2 microglobulin. The antigens are dimers of peptides with a molecular weight of approximately equal to 42,000 daltons and 12,000 daltons, respectively. This implies that TCA might be equivalent to either Qa or Tla in the mouse. For the TCB system no evidence is found for linkage with any known genetic marker. Only in random population studies is an association seen between TCB and Gm.

HLA-linked control of predisposition to lepromatous leprosy

In order to investigate if genes conferring susceptibility to leprosy and/or predisposition to a particular leprosy type are linked to HLA, we performed HLA-A and HLA-B typing on members of 29 families containing at least two siblings affected with leprosy from a leprosy endemic area in Jiangsu Province, People's Republic of China. Moreover, we performed a lepromin test in nearly all of the members of eight families containing at least two siblings affected with lepromatous leprosy. For 26 families the data permitted analyses of the segregation of parental HLA-haplotypes observed among children in relation to leprosy status. Siblings affected with lepromatous (LL or BL) leprosy shared parental HLA-haplotypes significantly more often than expected (p less than 0.05), and a highly significant deficit (p less than 0.0005) of shared HLA-haplotypes was observed among affected siblings discordant for leprosy type. These data confirm the HLA-linked control of leprosy type and, in particular, recently obtained evidence for linkage of predisposition to lepromatous leprosy with HLA. Healthy siblings did not share a haplotype more often than expected, and those haplotypes which were shared among all leprosy patients of a sibship did not occur less frequently than expected among the healthy siblings of the same sibship. The latter data confirm the absence of linkage of genes conferring susceptibility or resistance to leprosy with HLA. An analysis of the lepromin test results observed among healthy siblings showed no evidence for cosegregation of the results with HLA.

Automated reading of Propidium Iodide lymphocytotoxicity tests for HLA-DR, MB, MT typing

The combination of the Propidium Iodide method and automatic reading and scoring with a microscope fluorimeter is an accurate, reproducible and stable procedure for HLA-DR, MB and MT typing.

The recognition of abnormal sex chromosome constitution by HLA-restricted anti-H-Y cytotoxic T cells and antibody

Using the cell-mediated lympholysis (CML) technique, we studied lymphocytes of six individuals with discrepancies between the karyotypic and phenotypic sex. Two sets of cytotoxic T cells (CTLs) obtained from two multitransfused female aplastic anemia patients were used as typing reagents. These cells were previously shown to kill allogeneic target cells from HLA-A2- or B7-positive male donors. An antiserum obtained from one of the patients likewise killed HLA-A2 male lymphocytes. The six patients studied were selected for the required antigens. Positive reactions were obtained with lymphocytes from a 46,XY woman with pure gonadal dysgenesis and a 45,XO male. Target cells of the mother of the latter patient were also lysed. One individual with a 45,XO/46,X,del(Y)? karyotype was weakly positive, while three 46,XX males were completely negative. The reactivity of the HLA-A2-restricted H-Y-specific antibody showed the same discriminatory patterns. The results obtained by the HLA-restricted CTLs as well as by the antiserum did not correlate with the presence of testes as is the case in a different test system for the serologically detectable male (SDM) antigen in man. On the other hand, there was a correlation with the presence of cytologically detectable Y-chromosome material in five of the six individuals studied. The HLA-restricted CTLs and the antibody might recognize the classical transplantation antigen H-Y.

Recognition of a polymorphic monocyte antigen in HLA

The serological recognition of 'new' gene products of the HLA system can be accomplished by selecting sera with strong leucocyte antibodies and testing these against a panel of cells obtained from donors which are compatible for the known HLA antigens with the antibody producer. This approach, which we termed the HLA-CAP approach (compatible with antibody producer), was essential in the recognition of what is now called the HLA-DR locus and of non HLA-linked T-cell subgroups. Using the same technique, we have defined here several sera recognizing a structure on monocytes similar to one of the alleles of the HLA-linked PL3 or secondary B-cell (SB) system, so far only recognized by cellular techniques.

Cell membrane polymorphisms coded for in the HLA-D/DR region. I. Relation between D and DR

The relation of HLA-D and -DR determinants was studied in Dutch Caucasoids. The recognition of subgroups of DR4, DR5, and DR7, and the specificities LB12 and LB13 are described. Phenotype and gene frequencies and a Hardy--Weinberg analysis of DR and local (LB) B-cell groups are given. Excellent correlation between D and DR typing was obtained when HTCs were studied by selected B-cell antisera. When the same sera were used to type a panel of D typed cells, the correlation was decreased (with the exception of DR3 and Dw3). In the case of discrepancies the DR specificity, but not the corresponding D specificity, always could be found and not the other way around. The data fit best the assumption that HLA-D and -DR are carried by the same molecule, although they might be different determinants on this molecule. A number of possible explanations for the observed discrepancies has been given.

Major histocompatibility complex-restricted H-Y-specific antibodies and cytotoxic T lymphocytes may recognize different self determinants

Previous studies have shown that influenza virus-immune cytotoxic T lymphocytes can recognize virus in conjunction with self HLA-A2 antigens. Nevertheless, the virus-infected target cells from one HLA-A2-positive male donor (designated M7) could not be lysed by the virus-immune cytotoxic lymphocytes from any HLA-A2-matched unrelated donors. Although extensive serological analyses showed no difference between the HLA-A2 antigens of donor M7 and other HLA-A2-positive donors, isoelectric focusing of the HLA-A2 molecule from donor M7 revealed a clear difference in the heavy polypeptide chains when compared with the HLA-A2 molecules of other donors. The present study demonstrates that the HLA-A2-restricted anti-H-Y cytotoxic T lymphocytes obtained from a female aplastic anaemia patient fail to lyse the male M7 target cells, whereas the HLA-A2-restricted anti-H-Y antibodies from the same patient react with the cells of donor M7. These results suggest that: (a) HLA-A2-restricted anti-H-Y antibodies can recognize self determinants on the HLA-A2 molecule that are distinct from those that are recognized by HLA-A2-restricted anti-H-Y cytotoxic T cells; and (b) HLA-restricted T and B cells may use different receptor repertoires for the recognition of foreign antigens such as H-Y.

Di-allelic alloantigenic systems on subsets of T cells

Sera obtained from multiparous women and some of other origin contain antibodies which react with antigens on T cell subsets. These antibodies recognize two distinct diallelic systems, one of which is mainly present on T gamma cells while the other is present on T mu cells. The sera that reacted with the T gamma cells formed a pattern consistent with that of a diallelic system which we have called TCA system with alleles TCA 1 and TCA 2; the sera which reacted with the T mu cells formed a pattern consistent with another diallelic system, independent from TCA, which we have designated the TCB system, with alleles TCB 1 and TCB 2.

Human alloimmune sera against T cell subsets. Detection and influence on pokeweed mitogen-stimulated Ig production in vitro

Sera from multiparous women contain antibodies against T cell subsets. Population and family studies of four anti-T cell-subset antibodies are given. Two of these reacted with part of the suppressor T cell fraction (T gamma) and two with part of the helper T cell fraction (T mu) cells. By mixing T gamma- and mu-enriched cell suspensions in different concentrations, preliminary evidence was obtained that the anti-T cell-subset sera recognized T cells that had different functions in pokeweed mitogen-stimulated cytoplasmic immunoglobulin synthesis.

DR typing in Australian Aborigines. An indication for a second locus in the HLA--D region defined by serology

A group of 43 Australian Aborigines was typed for HLA--DR determinants and other antigens on B cells, using pregnancy sera from Caucasoid women. The group could not be considered as random, since a selection was made for an equal number of Au antigen positive and Au antigen negative individuals The typing results showed that the specificities DRw2, 4 and 8 were as well defined in this population as in Caucasoids, whereas the specificities DRw1, 3, 5 and 7 could not be defined. Even more interesting was the finding that a cluster of six sera, defining the local B cell specificity LB12, gave positive reactions in 41 out of 43 Aborigines. Although LB12 is found to be highly associated with DRw1, 2 and 6 in the Caucasoid population, in 36 cases the LB12 positive Aborigines could not be demonstrated to carry the specificities DRw1 or 2. The recognition of DRw6 is difficult at the moment and for the reason its presence or absence in this material is uncertain. However, three individuals typed positive for DRw4 and 8 and for LB12 as well. These findings strongly support the hypothesis that the genes coding for LB12 and its postulated allele LB13 are separate from the genes coding for the known DR determinants. LB12 is very likely identical to the recently described determinants DC1 (Tosi & Tanigaki 1979) and MB1 (Duquesnoy et al. 1979a).

HLA antigen distribution and HLA haplotype segregation in Crohn's disease

A study of the HLA-A, -B, -C, and -DR antigens in patients with Crohn's disease and controls did not reveal a significant strong association with a particular HLA antigens. A segregation analysis of parental HLA haplotypes in nine families with at least two children suffering from Crohn's disease did not show a significant deviation from the expected Mendelian segregation.