Novel C1q assay reveals a clinically relevant subset of human leukocyte antigen antibodies independent of immunoglobulin G strength on single antigen beads.

It has been known for 40 years that cytotoxic human leukocyte antigen (HLA) antibodies are associated with graft rejection. However, the complement-dependent cytotoxicity assay (CDC) used to define these clinically deleterious antibodies suffers from a lack of sensitivity and specificity. Recently, methods exploiting immunoglobulin G (IgG) antibody binding to HLA single antigen beads (SAB) have overcome sensitivity and specificity drawbacks but introduced a new dilemma: which of the much broader set of antibodies defined by these methods are clinically relevant. To address this, we developed a complement-fixing C1q assay on the HLA SAB that combines sensitivity, specificity, and functional potential into one assay. We compared the CDC, IgG, and C1q assays on 96 sera having 2,118 defined antibodies and determined that CDC detects only 19% of complement-fixing antibodies detected by C1q, whereas C1q detects only 47% of antibodies detected by IgG. In the same patient, there is no predictability by IgG mean fluorescence intensity (MFI) as to which of the antibodies will bind C1q because fixation is independent of MFI values. In 3 clinical studies, C1q(+) antibodies appear to be more highly correlated than those detected by IgG alone for antibody-mediated rejection in hearts as well as for kidney transplant glomerulopathy and graft failure.

A multi-site study using high-resolution HLA genotyping by next generation sequencing.

The high degree of polymorphism at human leukocyte antigen (HLA) class I and class II loci makes high-resolution HLA typing challenging. Current typing methods, including Sanger sequencing, yield ambiguous typing results because of incomplete genomic coverage and inability to set phase for HLA allele determination. The 454 Life Sciences Genome Sequencer (GS FLX) next generation sequencing system coupled with conexio atf software can provide very high-resolution HLA genotyping. High-throughput genotyping can be achieved by use of primers with multiplex identifier (MID) tags to allow pooling of the amplicons generated from different individuals prior to sequencing. We have conducted a double-blind study in which eight laboratory sites performed amplicon sequencing using GS FLX standard chemistry and genotyped the same 20 samples for HLA-A, -B, -C, DPB1, DQA1, DQB1, DRB1, DRB3, DRB4, and DRB5 (DRB3/4/5) in a single sequencing run. The average sequence read length was 250 base pairs and the average number of sequence reads per amplicon was 672, providing confidence in the allele assignments. Of the 1280 genotypes considered, assignment was possible in 95% of the cases. Failure to assign genotypes was the result of researcher procedural error or the presence of a novel allele rather than a failure of sequencing technology. Concordance with known genotypes, in cases where assignment was possible, ranged from 95.3% to 99.4% for the eight sites, with overall concordance of 97.2%. We conclude that clonal pyrosequencing using the GS FLX platform and CONEXIO ATF software allows reliable identification of HLA genotypes at high resolution.

Isolation, characterization, and transplantation of bone marrow-derived hepatocyte stem cells.

Recently it was shown that a population of cells in the bone marrow-expressing hematopoietic stem cell antigens could differentiate into hepatocytes. However, explicitly committed hepatocyte progenitors, which exhibit highly differentiated liver functions, immediately upon isolation, have not yet been isolated from bone marrow. After studying common antigens on blast-like cells in fetal and adult regenerating cholestatic rat livers and human regenerating and malignant livers, we hypothesized that beta-2-microglobulin-negative (beta(2)m(-)) cells might represent dedifferentiated hepatocytes and/or their progenitors. Utilizing a two-step magnetic bead cell-sorting procedure, we show that in bone marrow from rat and human, beta(2)m(-)/Thy-1(+) cells consistently express liver-specific genes and functions. After intraportal infusion into rat livers, bone marrow-derived hepatocyte stem cells (BDHSC) integrated with hepatic cell plates and differentiated into mature hepatocytes. In a culture system simulating liver regeneration and containing cholestatic serum, these cells differentiated into mature hepatocytes and metabolized ammonia into urea. This differentiation was dependent on a yet nondescript humoral signal existing in the cholestatic serum. Transmission electron microscopy and three-dimensional digital reconstruction confirmed hepatocyte ultrastructure of cultured BDHSC.

Posttransplant therapy using high-dose human immunoglobulin (intravenous gammaglobulin) to control acute humoral rejection in renal and cardiac allograft recipients and potential mechanism of action.

BACKGROUND: Intravenous gammaglobulin (i.v.IG) contains anti-idiotypic antibodies that are potent inhibitors of HLA-specific alloantibodies in vitro and in vivo. In addition, highly HLA-allosensitized patients awaiting transplantation can have HLA alloantibody levels reduced dramatically by i.v.IG infusions, and subsequent transplantation can be accomplished successfully with a crossmatch-negative, histoincompatible organ. METHODS: In this study, we investigated the possible use of i.v.IG to reduce donor-specific anti-HLA alloantibodies arising after transplantation and its efficacy in treating antibody-mediated allograft rejection (AR) episodes. We present data on 10 patients with severe allograft rejection, four of whom developed AR episodes associated with high levels of donor-specific anti-HLA alloantibodies. RESULTS: Most patients showed rapid improvements in AR episodes, with resolution noted within 2-5 days after i.v.IG infusions in all patients. i.v.IG treatment also rapidly reduced donor-specific anti-HLA alloantibody levels after i.v.IG infusion. All AR episodes were reversed. Freedom from recurrent rejection episodes was seen in 9 of 10 patients, some with up to 5 years of follow-up. Results of protein G column fractionation studies from two patients suggest that the potential mechanism by which i.v.IG induces in vivo suppression is a sequence of events leading from initial inhibition due to passive transfer of IgG to eventual active induction of an IgM or IgG blocking antibody in the recipient. CONCLUSION: I.v.IG appears to be an effective therapy to control posttransplant AR episodes in heart and kidney transplant recipients, including patients who have had no success with conventional therapies. Vascular rejection episodes associated with development of donor-specific cytotoxic antibodies appears to be particularly responsive to i.v.IG therapy.

Cw*1701 defines a divergent african HLA-C allelic lineage.

The complete sequence of a new HLA-C allele, Cw*1701, was determined from a South African Zulu individual. Unique features that distinguish Cw*1701 from other HLA-C alleles include multiple point substitutions and an 18 nucleotide insertion in exon 5, which encodes the transmembrane domain. In a phylogenetic analysis of HLA-C sequences, Cw*1701 forms a third, distinct allelic lineage. A comparison of the transmembrane domain of Cw*1701 with other HLA-B and -C alleles reveals that duplications and deletions have been common in the evolution of these loci. A polymerase chain reaction based typing method was used to determine the distribution of this unusual allele in human populations. In contrast to the other two lineages of HLA-C alleles, the Cw*17 lineage is found at high frequencies only in populations of African descent. In addition, the HLA-B/Cw*17 haplotype diversity is higher in Africa.

A new syndrome of Crohn's disease and pachydermoperiostosis in a family.

Few syndromic associations with Crohn's disease are described. The aim of this study was to characterize a new syndrome of Crohn's disease associated with pachydermoperiostosis in 3 brothers. Three probands, 6 siblings, both parents, 20 of 21 third-generation relatives, and 9 spousal controls were evaluated. Serological evaluation for antineutrophil cytoplasmic antibodies and human leukocyte antigens as well as genetic testing for tumor necrosis factor microsatellites, intercellular adhesion molecule 1 polymorphisms, the interleukin 1 receptor antagonist gene, and the interleukin 1 beta gene were performed. Only the 3 probands were affected and developed pachydermoperiostosis between ages 14 and 17 years. Pachydermoperiostosis preceded Crohn's ileocolitis by 6 and 20 years in two probands, excluding secondary hypertrophic osteoarthropathy. Two probands were antineutrophil cytoplasmic antibody positive vs. 1 of 27 unaffected relatives (P < 0.001, chi 2). Haplotypes for human leukocyte antigen and tumor necrosis factor microsatellites were discordant. The probands' generation was homozygous for the common allele 1 of the interleukin 1 receptor antagonist and interleukin 1 beta genes. Two probands carried a rare polymorphism of the intercellular adhesion molecule 1 gene. A new syndrome of Crohn's disease and pachydermoperiostosis associated with antineutrophil cytoplasmic antibodies is described. Inheritance is most likely autosomal recessive by pedigree. No clear association was found between this syndrome and the gene regions evaluated.

HLA-B16 antigens: sequence of the ST-16 antigen, further definition of two B38 subtypes and evidence for convergent evolution of B*3902.

The ST-16 antigenic specificity of the HLA-B locus is defined as a B39 variant of Mexican-Americans. Nucleotide sequencing of cDNA shows the ST-16 allele (B*3905) differs from B*39011 by a single substitution that substitutes tyrosine for aspartic acid at position 74 of the mature class I heavy chain. The complete coding region sequence for the common caucasoid allele encoding the B38 antigen has been determined. This B*3801 allele differs from B*3802 at two nucleotide substitutions within the Bw4 sequence motif. B*3801 and B*3802 may have been derived independently from B*39011 by conversion events with B alleles donating distinctive Bw4 motifs. A novel allele B*39022 derived from a Colombian Indian differs from the B*39021 allele of Japanese origin at two widely separated silent substitutions. Comparison of sequences for the known B16 alleles suggest that B*39021 and B*39022 were independently derived by recombination from B*39013 and B*39011 respectively.

Intravenous immunoglobulin suppression of HLA alloantibody in highly sensitized transplant candidates and transplantation with a histoincompatible organ.

Patients awaiting solid organ transplantation who are highly sensitized to HLA antigens remain problematic in terms of finding compatible (crossmatch-negative) donors. We have used intravenous gammaglobulin (IVIG; 10% Gamimune N) to determine both its efficacy in reducing panel-reactive antibodies in vitro and the prognostic value of the in vitro testing for in vivo efficacy. In 18 patients with PRAs ranging from 40 to 100% (mean: 77%) we found a reduction in absolute PRA of 4-70% (mean decrease: 35%; percent inhibition: 4-100%; residual PRA 0-96%). In 7 cases, the residual antibody specificity could be easily determined and often appeared to include a short HLA-A2. This was independent of A2 subtype as determined by PCR-SSOP. Testing the IVIG on a panel of 21 HLA reagent alloantisera resulted in heterogeneous inhibitory patterns (7 complete, 3 partial, 8 differential, 3 none) independent of titer or specificity. In vivo administration to a 13-year-old kidney patient awaiting retransplant resulted in a PRA drop from 95% to 15% and successful retransplantation (now 11 months post-transplant). More impressively, successive in vivo administration of IVIG to a sensitized (anti-HLA-A2, A68, A69; B57, B58) heart transplant candidate resulted in successful transplantation with an A2+ histoincompatible heart. The patient experienced only one subclinical humoral rejection in the first 5 months posttransplant. Biochemical studies to determine the effective component of IVIG show that it is the IgG fraction and not soluble antigen or the minor IgM or IgA contaminants that is responsible. This suggests an antiidiotypic modulation of anti-HLA antibodies in vitro and in vivo.

Vitamin A-enhanced cleft palate susceptibility gene maps between C4 and B144 within the H-2 complex.

Pregnant mice congenic with C57BL/10 in the region of H-2, the major histocompatibility complex on Chromosome 17 (B10.BR, B10.A, B10.A(1R), B10.A(2R), B10.A(15R), B10.A(18R), B10.OL, or crosses between them) were fed Purina Laboratory Chow or the same diet plus 400 IU of vitamin A daily from conception and given dexamethasone (80 or 160 mg/kg) intraperitoneally on the twelfth day of pregnancy. It was found that the added vitamin A increased the frequency of isolated cleft palate only in strains that had b alleles between C4 and B144. The enhancement of susceptibility to glucocorticosteroid-induced cleft palate by vitamin A appears to be a recessive trait and the locus, called Acp, maps centromeric to another corticosteroid-induced cleft palate gene (Dcp-2) that also is in the C4:B144 interval.

Familial Mediterranean fever--linkage studies with genetic markers on chromosome 6.

Familial Mediterranean Fever (FMF) is an autosomal recessive disease manifested by recurrent short episodes of fever associated with polyserositis. Although the biochemical defect is unknown, there are several immunologic abnormalities which have been described in this disease. To examine critically whether there is linkage between FMF and the immunogenetic region (major histocompatibility complex-MHC) on chromosome 6, including the HLA, BF, and GLO1 loci, blood samples from members of 13 nuclear Armenian families were tested for these genetic markers. These 13 families included 28 affected and 42 unaffected family members. Linkage could be excluded at 7.5% recombination with the HLA ABC and D loci. Linkage could be excluded at 2.5% recombination for GLO1. Linkage could not be excluded with BF individually, but can be rejected based on the haplotype data. No association was found with either BF, GLO1, and HLA DQ alleles. HLA DR4 was found more often in affected cases than in controls; however, after adjusting for the number of antigens tested this was not significant. Our results would appear to exclude the immunogenetic region on chromosome 6 from linkage with FMF in the Armenian population.