Intravenous gammaglobulin (IVIG): a novel approach to improve transplant rates and outcomes in highly HLA-sensitized patients

Intravenous immunoglobulin (IVIG) products are derived from pooled human plasma and have been used for the treatment of primary immunodeficiency disorders for more than 24 years. Shortly after their introduction, IVIG products were also found to be effective in the treatment of autoimmune and inflammatory disorders. Over the past 2 decades, the list of diseases where IVIG has a demonstrable beneficial effect has grown rapidly. These include Kawasaki disease, Guillain-Barre syndrome, myasthenia gravis, dermatomyositis and demyelinating polyneuropathy. Recently, we have described a beneficial effect on the reduction of anti-HLA antibodies with subsequent improvement in transplantation of highly HLA-sensitized patients as well as a potent anti-inflammatory effect that is beneficial in the treatment of antibody-mediated rejection (AMR). These advancements have enabled transplantation of patients previously considered untransplantable. These studies and relevant mechanism(s) of action will be discussed here.

Intravenous immune globulin treatment inhibits crossmatch positivity and allows for successful transplantation of incompatible organs in living-donor and cadaver recipients

BACKGROUND

Sensitization to human leukocyte antigens (HLA) is a significant barrier to transplantation. Currently, no proven therapy exists to improve access to transplantation for highly sensitized patients. Here, we report a novel approach using intravenous immune globulin to modulate anti-HLA antibody and improve the chances for successful transplantation.

PATIENTS AND METHODS

Forty-five highly HLA-sensitized patients presented as candidates for living-donor kidney transplantation (n=28), cadaveric kidney transplantation (n=15), or heart transplantation (n=2). All patients had a positive CDC crossmatch (CMX) with their donors. In living-donor recipients, intravenous immune globulin (IVIG) was added to the CMX evaluation to determine whether blocking antibodies present in IVIG could inhibit cytotoxicity. For those who showed in vitro inhibition with IVIG (n=26), IVIG was administered (usually as a single dose, 2 g/kg) and the CDC CMX was repeated against the prospective donor immediately after IVIG infusion. If negative, the patient underwent transplantation with their living-donor kidney within 24 to 72 hr. A similar but modified protocol was performed for cadaver donor candidates, all of whom were highly sensitized and had had CMX positivity with multiple donors, negating transplantation. Reductions in CMX positivity, posttransplantation serum creatinine level, number and severity of rejection episodes, and patient and graft survival rates were determined.

RESULTS

Forty-two patients underwent transplantation. IVIG treatment completely abrogated the donor-specific CMXs in 35 of 42 patients. In the remaining 7 patients, the CDC CMX was inhibited, but flow cytometry CMXs remained positive. A total of 13 (31%) of 42 recipients developed rejection episodes 3 to 49 days after transplantation. Three grafts (7%) were lost to rejection. Mean serum creatinine level at 24 months was 1.4+/-0.4 mg/dL. Patient and graft survival rates were 97.6% and 89.1%, respectively, at 24 months.

CONCLUSIONS

The in vitro IVIG CMX technique predicts the ability of IVIG to reduce anti-HLA antibody levels in highly sensitized patients. Subsequent in vivo IVIG treatment of responders eliminates the positive CDC CMX and allows for successful transplantation. Thus a positive CMX result is not necessarily a contraindication for transplantation and allows access to transplantation for patients for whom it was previously contraindicated.

HLA class II haplotype associations with inflammatory bowel disease in Jewish (Ashkenazi) and non-Jewish caucasian populations

Ulcerative colitis (UC) and Crohn's disease (CD) are the clinical entities comprising idiopathic inflammatory bowel disease (IBD). Previous studies on the association of IBD and human leukocyte antigen (HLA) class II genes suggested a role for HLA in this disease. Here we present HLA class II (DRB1, DQB1, DQA1, DPB1) allele and haplotype distributions determined using the polymerase chain reaction and sequence-specific oligonucleotide probe methods. A total of 578 UC and CD Caucasian patients and controls from Jewish (Ashkenazi) and non-Jewish populations was examined. Our previously reported association of DR1-DQ5 with CD was attributable to DRB1*0103. A dramatic association with IBD and the highly unusual DRB1*0103-DQA1*0501-DQB1*0301 haplotype (OR = 6.6, p = 0.036) was found. The more common DR1 haplotype, DRB1*0103-DQA1*0101-DQB1*0501, was also associated with IBD (OR = 3.1, p = 0.014), a result suggesting that interaction between DR and DQ may determine the extent of disease risk. Our previously reported association of DR2 with UC was attributable to DRB1*1502 (OR = 2.6, p = 0.006). At the DPB1 locus, a significant association of DPB1*0401 with CD was observed for the combined populations (OR = 1.85, p = 0.007). These observations indicate that some class II alleles and haplotypes confer susceptibility to both UC and CD, implying common immunogenetic mechanisms of pathogenesis, while others confer risk to only one of these diseases, and illustrate the value of DNA HLA typing in disease susceptibility analyses.

Linkage of Crohn's disease to the major histocompatibility complex region is detected by multiple non-parametric analyses

BACKGROUND

There is evidence for genetic susceptibility to Crohn's disease, and a tentative association with tumour necrosis factor (TNF) and HLA class II alleles.

AIMS

To examine the potential of genetic linkage between Crohn's disease and the MHC region on chromosome 6p.

METHODS

TNF microsatellite markers and, for some families, additional HLA antigens were typed for 323 individuals from 49 Crohn's disease multiplex families to generate informative haplotypes. Non-parametric linkage analysis methods, including sib pair and affected relative pair methods, were used.

RESULTS

Increased sharing of haplotypes was observed in affected sib pairs: 92% (48/52) shared one or two haplotypes versus an expected 75% if linkage did not exist (p=0.004). After other affected relative pairs were included, the significance level reached 0.001. The mean proportion of haplotype sharing was increased for both concordant affected (pi=0.60, p=0.002) and unaffected sib pairs (pi=0.58, p=0. 031) compared with the expected value (pi=0.5). In contrast, sharing in discordant sib pairs was significantly decreased (pi=0.42, p=0. 007). Linear regression analysis using all three types of sib pairs yielded a slope of -0.38 at p=0.00003. It seemed that the HLA effect was stronger in non-Jewish families than in Jewish families.

CONCLUSIONS

All available analytical methods support linkage of Crohn's disease to the MHC region in these Crohn's disease families. This region is estimated to contribute approximately 10-33% of the total genetic risk to Crohn's disease.

Immunomodulatory actions of intravenous immunoglobulin (IVIG): potential applications in solid organ transplant recipients

Intravenous gammaglobulin (IVIG) products are known to have powerful immunomodulatory and anti-inflammatory functions in vitro and in vivo. In addition, IVIG has shown benefit in the treatment of many human autoimmune and inflammatory disorders. One potential mechanism of action responsible for these beneficial effects is the down-regulation of deleterious autoantibody titers through idiotypic-anti-idiotypic networks. Until recently, few data were available on the use of IVIG in the management of alloimmune disorders. In this review, we will discuss current data on the use of pooled human gammaglobulin as an agent with potential to regulate undesirable alloimmune responses and allosensitization through similar idiotypic-anti-idiotypic circuits and how this therapy could be of benefit in the management of highly sensitized patients both pre- and post-transplant. We will also discuss other potential anti-inflammatory and immunoregulatory mechanisms induced by IVIG treatment and how these may be applied to improve transplantability and outcomes in human transplantation.

Human diversity in killer cell inhibitory receptor genes

The presence and expression of killer inhibitory receptor (KIR) and CD94:NKG2 genes from 68 donors were analyzed using molecular typing techniques. The genes encoding CD94:NKG2 receptors were present in each person, but KIR gene possession varied. Most individuals expressed inhibitory KIR for the three well-defined HLA-B and -C ligands, but noninhibitory KIR genes were more variable. Twenty different KIR phenotypes were defined. Two groups of KIR haplotypes were distinguished and occurred at relatively even frequency. Group A KIR haplotypes consist of six genes: the main inhibitory KIR, one noninhibitory KIR, and a structurally divergent KIR. Allelic polymorphism within five KIR genes was detected. Group B comprises more noninhibitory KIR genes and contains at least one additional gene not represented in group A. The KIR locus therefore appears to be polygenic and polymorphic within the human population.

Heterogeneous phenotypes of expression of the NKB1 natural killer cell class I receptor among individuals of different human histocompatibility leukocyte antigens types appear genetically regulated, but not linked to major histocompatibililty complex haplotype

Natural killer (NK) cells that express the NKB1 receptor are inhibited from killing target cells that possess human histocompatibility leukocyte antigen (HLA) B molecules bearing the Bw4 serological epitope. To investigate whether NKB1 expression is affected by HLA type, peripheral blood lymphocytes of 203 HLA-typed donors were examined. Most donors had a single population of NKB1+ cells, but some had two populations expressing different cell surface levels of NKB1, and others had no detectable NKB1+ cells. Among the donors expressing NKB1, both the relative abundance of NKB1+ NK cells and their level of cell surface expression varied substantially. The percentage of NKB1+ NK cells ranged from 0 to >75% (mean 14.7%), and the mean fluorescence of the positive population varied over three orders of magnitude. For each donor, the small percentage of T cells expressing NKB1 (usually <2%), had a pattern of expression mirroring that of the NK cells. NKB1 expression by NK and T cells remained stable over the 2-yr period that five donors were tested. Patterns of NKB1 expression were not associated with Bw4 or Bw6 serotype of the donor or with the presence of any individual HLA-A or -B antigens. Cells expressing NKB1 are often found in donors who do not possess an appropriate class I ligand, and can be absent in those who express Bw4+ HLA-B antigens. Family studies further suggested that the phenotype of NKB1 expression is inherited but not HLA linked. Whereas identical twins show matching patterns of NKB1 expression, HLA-identical siblings can differ in NKB1 expression, and conversely, HLA-disparate siblings can be similar. Thus NKB1 expression phenotypes are tightly regulated and extremely heterogeneous, but not correlated with HLA type.

Testing the importance of each residue in a HLA-B27-binding peptide using monoclonal antibodies

When a peptide derived from histone 3.3 was incubated with mouse L cells transfected with HLA-B27, the cells became highly reactive with Ye-2, an anti-HLA-B27 mAb. The critical residues were analyzed by testing analogues in which each of the nine residues in the peptide was consecutively substituted by 19 other amino acids. The conclusions were separately verified using a different HLA-B27-positive cell line. The ability of some of these peptides to bind to HLA-B27 was also assayed by their ability to stabilize HLA-B27 in a mutant cell line which required HLA-B27-binding peptides to express HLA-B27 at 37 degrees C. These experiments showed that in P4, P5, P6, P7, P8, and P9, all 20 different amino acids could be substituted without eliminating the ability of the analogues to bind to HLA-B27. The residues which were responsible for the HLA-B27-peptide complex reacting with the Ye-2 antibody were P8 and P9. The latter might mediate its effect by altering either the surface conformation of the closely associated HLA-B27 heavy chain or the conformation of the peptide itself.

Testing the importance of each residue in a HLA-B27-binding peptide using monoclonal antibodies

When a peptide derived from histone 3.3 was incubated with mouse L cells transfected with HLA-B27, the cells became highly reactive with Ye-2, an anti-HLA-B27 mAb. The critical residues were analyzed by testing analogues in which each of the nine residues in the peptide was consecutively substituted by 19 other amino acids. The conclusions were separately verified using a different HLA-B27-positive cell line. The ability of some of these peptides to bind to HLA-B27 was also assayed by their ability to stabilize HLA-B27 in a mutant cell line which required HLA-B27-binding peptides to express HLA-B27 at 37 degrees C. These experiments showed that in P4, P5, P6, P7, P8, and P9, all 20 different amino acids could be substituted without eliminating the ability of the analogues to bind to HLA-B27. The residues which were responsible for the HLA-B27-peptide complex reacting with the Ye-2 antibody were P8 and P9. The latter might mediate its effect by altering either the surface conformation of the closely associated HLA-B27 heavy chain or the conformation of the peptide itself.

Distinct associations of HLA class II genes with inflammatory bowel disease

BACKGROUND

There are relatively few studies of HLA class II association either with Crohn's disease (CD) or ulcerative colitis (UC). The few available association studies have been carried out by serological techniques, and the results from these studies are inconclusive.

METHODS

The association between HLA class II genes was studied using molecular genotyping in combination with allele-specific oligonucleotide hybridization by polymerase chain reactions.

RESULTS

In UC (n = 74), we observed a positive association with the HLA DR2 allele (P = 0.008) and negative associations with the DR4 (P = 0.018) and DRw6 (P = 0.028) when compared with ethnically matched controls (n = 77). No associations were observed with any DQ alleles. In contrast, in CD (n = 95) we observed a positive association with the combination of DR1 and DQw5 alleles (P = 0.021). Furthermore, stratifying DR1 and DQw5 alleles indicated that neither allele was independently associated with CD, suggesting that the association was with the haplotype rather than either of the alleles individually. A suballele of DQw5, DQB1*0501, contributed this haplotypic association (P = 0.012).

CONCLUSIONS

DR and DQ molecules firmly separate UC and CD on genetic grounds, suggesting that the contribution of the HLA class II genes to the disease susceptibility is quite different for the two disorders.

Restriction fragment length polymorphism (RFLP) heterogeneity of HLA-DQ beta genes associated with DNA fragment identical to the DR1-beta DNA structure

Restriction fragment length polymorphism (RFLP) analyses of DR1 positive peripheral blood leukocytes DNA was carried out. The Taq I digested DNA was hybridized with cDNA probes for HLA-DR and -DQ beta genes. The DR probe detected fragments commonly observed in the DR1 specificity, whereas a new DQ-beta fragment was detected in some DR1 haplotypes when the DQ-beta probe was used. This fragment had an RFLP pattern identical to the DQ-beta fragment typically associated with most DR2 and some DRw6 specificities.

Use of RecA protein to enrich for homologous genes in a genomic library

RecA protein-coated probe has been utilized to enrich genomic digests for desired genes in order to facilitate cloning from genomic libraries. Using a previously cloned HLA-B27 gene as the recA-coated enrichment probe, we obtained a mean 108x increase in the ratio of specific to nonspecific plaques in lambda libraries screened for B27 variant alleles of estimated 99% homology to the probe. Class I genes of lesser homology were less enriched: 6.7x for non-B27 genes of estimated greater than 95% homology and 3.7x for other-Class I genes of greater than 80% homology. Loss of genomic DNA during the enrichment procedure can, however, restrict application of this technique whenever starting genomic DNA is very limited. Nevertheless, the impressive reduction in cloning effort and material makes recA enrichment a useful new tool for cloning homologous genes from genomic DNA.