Collection and processing of whole blood for transformation of peripheral blood mononuclear cells and extraction of DNA: the Type 1 Diabetes Genetics Consortium.

BACKGROUND: and PURPOSE: To yield large amounts of DNA for many genotype analyses and to provide a renewable source of DNA, the Type 1 Diabetes Genetics Consortium (T1DGC) harvested DNA and peripheral blood mononuclear cells (PBMCs) from individuals with type 1 diabetes and their family members in several regions of the world. METHODS: DNA repositories were established in Asia-Pacific, Europe, North America, and the United Kingdom. To address region-specific needs, different methods and sample processing techniques were used among the laboratories to extract and to quantify DNA and to establish Epstein-Barr virus transformed cell lines. RESULTS: More than 98% of the samples of PBMCs were successfully transformed. Approximately 20-25 microg of DNA were extracted per mL of whole blood. Extraction of DNA from the cell pack ranged from 92 to 165 microg per cell pack. In addition, the extracted DNA from whole blood or transformed cells was successfully utilized in each regional human leukocyte antigen genotyping laboratory and by several additional laboratories performing consortium-wide genotyping projects. LIMITATIONS: Although the isolation of PBMCs was consistent among sites, the measurement of DNA was difficult to harmonize. CONCLUSIONS: DNA repositories can be established in different regions of the world and produce similar amounts of high-quality DNA for a variety of high-throughput genotyping techniques. Furthermore, even with the distances and time necessary for transportation, highly efficient transformation of PBMCs is possible. For future studies/trials involving several laboratories in different locations, the T1DGC experience includes examples of protocols that may be applicable. In summary, T1DGC has developed protocols that would be of interest to any scientific organization attempting to overcome the logistical problems associated with studies/trials spanning multiple research facilities, located in different regions of the world.

The single antigen expressing lines (SALs) concept: an excellent tool for screening for HLA-specific antibodies.

Definition of the antibody specificity in the serum of patients waiting for a renal transplant or in need for platelet transfusion is a crucial step for finding adequate donors. Confounding factors are the complexity of the serum antibodies and the expression of several, up to six, different human leukocyte antigens (HLA) on peripheral blood lymphocytes used as target cells in the antibody screening. Single antigen-expressing (SAL) cell lines were generated by transfecting human major histocompatibility complex (MHC) class I sequences into K562, an erythroleukemia-derived cell line lacking MHC class I and II expression. Thirty-seven different SALs have been generated so far. In this study, we present the validation of 16 of those SALs by flow cytometry against a panel of 84 human HLA-specific monoclonal antibodies (30 HLA-A [8 IgG/22 IgM], 45 HLA-B [18 IgG/27 IgM], 6 HLA-A, B [3 IgG/3 IgM], and 3 HLA-C [all IgM]) developed in our laboratory. The SALs proved to be suitable tools to determine acceptable mismatches for highly sensitized patients. This concept of transfecting target sequences in immortalized cell lines opens up new avenues in the definition of serum and cellular reactivity for sensitized patients awaiting a suitable organ or blood component.

HLA matching and hematopoietic cell transplant outcome.

The development of accurate and reproducible high-resolution DNA-based HLA typing methods has significantly improved the prospects for identifying well-matched donors for patients undergoing HCT, particularly those who lack a matched relative to serve as donor. Analysis of high-resolution typing data has shown that donor-recipient compatibility for HLA alleles is an important predictor of transplant outcome. The risk of graft failure is increased by patient incompatibility for HLA alleles expressed by the donor, and by the presence of patient anti-donor alloantibody. The impact of HLA class I and class II allele disparity on transplant outcome in unrelated HCT has been demonstrated in several large studies, and it is now evident that complete donor-recipient matching for HLA-A,-B,-C,-DRB1 and -DQB1 genes can significantly reduce the incidence of GVHD and risk of mortality. Patient-donor disparity for multiple HLA class I and class II alleles is clearly related to poor outcome, in terms of both risk of severe GVHD and mortality. Important questions for future investigation include elucidation of the relative importance of matching for different HLA genes ("permissive" versus "non-permissive" alleles), and the potential synergistic impact of multi-locus class I and II disparities.

Killer Ig-like receptor haplotype analysis by gene content: evidence for genomic diversity with a minimum of six basic framework haplotypes, each with multiple subsets.

Killer Ig-like receptor (KIR) genes constitute a multigene family whose genomic diversity is achieved through differences in gene content and allelic polymorphism. KIR haplotypes containing a single activating KIR gene (A-haplotypes), and KIR haplotypes with multiple activating receptor genes (B-haplotypes) have been described. We report the evaluation of KIR gene content in extended families, sibling pairs, and an unrelated Caucasian panel through identification of the presence or absence of 14 KIR genes and 2 pseudogenes. Haplotype definition included subtyping for the expressed and nonexpressed KIR2DL5 variants, for two alleles of pseudogene 3DP1, and for two alleles of 2DS4, including a novel 2DS4 allele, KIR1D. KIR1D appears functionally homologous to the rhesus monkey KIR1D and likely arose as a consequence of a 22 nucleotide deletion in the coding sequence of 2DS4, leading to disruption of Ig-domain 2D and a premature termination codon following the first amino acid in the putative transmembrane domain. Our investigations identified 11 haplotypes within 12 families. From 49 sibling pairs and 17 consanguineous DNA samples, an additional 12 haplotypes were predicted. Our studies support a model for KIR haplotype diversity based on six basic gene compositions. We suggest that the centromeric half of the KIR genomic region is comprised of three major combinations, while the telomeric half can assume a short form with either 2DS4 or KIR1D or a long form with multiple combinations of several stimulatory KIR genes. Additional rare haplotypes can be identified, and may have arisen by gene duplication, intergenic recombination, or deletions.

Limits of HLA mismatching in unrelated hematopoietic cell transplantation.

HLA matching between the donor and recipient improves the success of unrelated hematopoietic cell transplantation (HCT). Matched donors are available for only a minority of patients. Further information is needed to evaluate the limits of HLA mismatching. We examined the association of mortality with HLA-A, -B, -C, -DRB1, and -DQB1 mismatching in 948 patients who received a T-replete unrelated HCT for treatment of a marrow disorder. A single HLA allele or antigen mismatch was associated with increased mortality among patients with chronic myeloid leukemia (CML) within 2 years after diagnosis compared to patients with no HLA mismatch, but not among those with more advanced malignancy. In particular, a single HLA-C mismatch conferred increased risk of mortality compared to matches. There was a suggestion for increased mortality with multiple mismatches involving HLA-DQB1 compared to multiple mismatches not involving HLA-DQB1. Donors with a single HLA allele or antigen mismatch may be used for HCT when a fully matched donor is not available for patients with diseases that do not permit time for a lengthy search. Whenever possible, HLA-C mismatches should be avoided for patients with early stage CML, and HLA-DQB1 mismatches should be avoided for patients with multiple mismatches.