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Beyond the HLA typing age: genetic polymorphisms predicting transplant outcome.

Although histocompatibility testing and matching for histocompatibility leukocyte antigens (HLA) remains the "state of the art" for determining donor selection, non-HLA encoded genes such as those for minor histocompatibiity antigens also play an important role in determining haematopoietic stem cell transplantation (HSCT) outcome. Single nucleotide polymorphisms (SNPs) within the promoter regulatory regions of non-HLA encoded genes such as those for cytokines and cytokine receptors which regulate the production of such molecules may also play a role in determining the extent of post-transplant complications. Mannose binding lectin genes (MBL) and other genes such as those for myeloperoxidase (MPO) and Fcgamma receptor may aid in the control of infection post transplant. This review will summarise the latest research concerning this area of predicting HSCT outcome and indicate the potential clinical use of the results.

Graft Survival↗

Multilaboratory evaluation of serum analysis for HLA antibody and crossmatch reactivity by lymphocytotoxicity methods.

CONTEXT: This report presents results of the serum antibody analysis and crossmatch challenges in the proficiency testing program for histocompatibility testing jointly sponsored by the American Society for Histocompatibility and Immunogenetics and the College of American Pathologists. OBJECTIVE: To obtain information about consensus rates among participating laboratories that reported antibody screening and crossmatch results by direct complement-dependent lymphocytotoxicity (CDC) and/or anti-human globulin (AHG)-augmentation methods. DESIGN: We analyzed responses from approximately 165 laboratories participating in 32 surveys during 1993-2000. Most of the testing was done by CDC methods, but increasing proportions of laboratories are using AHG augmentation of these techniques; almost one half of the serum screenings and crossmatches were done by AHG. RESULTS: A total of 40 serum specimens were screened to determine the percent panel-reactive antibody (PRA) and identify HLA-specific antibodies. Participants often reported very wide ranges of PRA values. Panel-reactive antibody ranges exceeded 60 percentage points for 16 (40%) of the serum screening results by CDC and for 31 (77%) of the results by AHG. The interlaboratory variability of PRA values suggests that in many laboratories, the CDC or AHG procedures were often too insensitive or overly sensitive. The antibody identification results revealed inconsistent patterns among the participants performing CDC or AHG screening. Most participants reported the same primary antibody specificities by both methods. The consensus levels were generally high for the monospecific sera. On the other hand, there was much less agreement among the participants if the sera reacted with 2 or more HLA antigens. Participants using the more sensitive AHG method reported additional antibody specificities in many specimens, but invariably the consensus levels were rather low. A total of 192 serum-cell combinations were used for the crossmatch challenges. There was considerable interlaboratory variability; 21% of the CDC crossmatches and 36% of AHG crossmatches failed to reach the 90% consensus threshold. CONCLUSIONS: This experience demonstrates considerable inconsistencies in serum screening and crossmatching among laboratories participating in the American Society for Histocompatibility and Immunogenetics/College of American Pathologists surveys. A lack of uniformity in test results may limit the efficient application of these methods in a clinical setting. Standardization of crossmatch and antibody screening techniques is highly desirable.

Antibody Specificity↗

Error rate for HLA-B antigen assignment by serology: implications for proficiency testing and utilization of DNA-based typing methods.

Until recently, the majority of HLA class I typing has been performed by serology. Expensive commercial typing trays are frequently used for testing non-Caucasian subjects and new strategies using DNA-based methods have been adopted for improving clinical histocompatibility testing results and adapted as supplements in proficiency testing. A double-blind comparison of the typing of HLA-B specificities in 40 samples was carried out between serology and two polymerase chain reaction (PCR) methods, PCR amplification with sequence-specific primers (PCR-SSP) and PCR amplification and subsequent hybridization with sequence-specific oligonucleotide probes (PCR-SSOP). The results demonstrated 22.5% misassignments of HLA-B antigens by serology. There was complete concordance between the results obtained with the two PCR based typing methods. A second panel of 20 donor samples with incomplete or ambiguous serologic results was analyzed by PCR-SSP and SSOP Both PCR methods identified correctly the HLA-B antigens. Our results suggest that more accurate typing results can be achieved by complementing serologic testing with DNA-based typing techniques. The level of resolution for HLA-B antigen assignment can be obtained by this combination of serology and limited DNA-based typing is equivalent to the HLA-B specificities defined by the WHO-HLA Committee. This level of resolution cannot routinely be achieved in clinical histocompatibility testing or in proficiency testing using serologic reagents only.

DNA↗

Factors influencing the outcome of kidney transplants.

This study is a multifactorial analysis of 389 transplants performed from June 1977 to December 1981. Analysis of the effects of transfusions antilymphocyte serum (ALS), histocompatibility testing, gender, and patient risk factors (presence of concomitant disease, greater than 50 years of age, etc.) was done. Two-hundred fifty-three patients received cadaver kidneys and 136 patients obtained kidneys from a relative. Two-hundred eighty-three (73%) patients received blood transfusions prior to transplantation. Our data showed that recipients receiving transfusions prior to transplantation had a significantly higher graft survival than those who were not transfused in both cadaveric and related graft recipients. Two-hundred twenty-one (56%) patients received ALS following the transplant. This group had a 15% higher graft survival than a comparable group. Analysis of histocompatibility testing data shows approximately 5% higher functional graft survival between each match grade. Surprisingly, female patients receiving kidneys from living related donors had a 16% higher graft survival than male patients. In cadaver recipients female patients had a 10% higher patient survival as compared to male patients. The risk factor status of recipients affected not only graft survival but patient survival, which probably is due to the consequences of immunotherapy. The authors' conclusion is that the above mentioned factors may be additive in nature. Further, multivariable analysis is necessary in order to correctly transplant data.

Antilymphocyte Serum↗

Marrow grafts between canine siblings matched by serotyping and mixed leukocyte culture.

Marrow grafts were carried out between 16 canine sibling donor-recipient pairs. The pairs were matched by serological histocompatibility testing and were nonreactive in a one-way mixed leukocyte culture. Recipients were prepared for transplantation by 1500-1580 R of total body irradiation. Donor marrow was infused within 4 hr of irradiation. Recipients were not given immunosuppressive drug therapy after grafting. All 16 recipients showed evidence of prompt and sustained allogeneic marrow engraftment. Six died between 30 and 128 days after grafting with graft-versus-host disease, and three died between days 72 and 230 with pneumonia but no evidence of graft-versus-host disease with the exception of lymphoid atrophy. Seven recipients survived without graft-versus-host disease and are in excellent health between 200 and 684 after grafting. In summary, fatal graft-versus-host disease was observed in a number of canine recipients despite matching with their sibling donor by serological histocompatibility testing and by mixed leukocyte culture in a manner similar to that employed to define human HL-A matched sibling pairs. The graft-versus-host disease in these matched siblings developed more slowly than that observed in mismatched dogs, but the ultimate death of approximately half of the matched recipients emphasizes the need for posttransplantation immunosuppression even in this "compatible" situation.

Animals↗

A rapid method for preimmunisation and grafting of mice with ear skin.

A schedule for a histocompatibility test among mice involving preimmunisation with ear skin is described and has been tested with the weak transplantation antigen H-Y in C57BL responder and C3H nonresponder strains. The transplantation technique was tested by autografting, and more than 99% of the operations were successful. The priming method reduces the survival of ear skin grafts in every combination tested.

Animals↗

[Comparison of the results of HLA typing using serologic and molecular genetics methods].

A comparison of the HLA class I typing in 50 unrelated individuals by means of serological and molecular genetic (PCR-SSP) methods was carried out. DNA-typing is more fast and reliable method in comparison with serology. It is necessary to introduce molecular genetic methods for the detection of HLA class I alleles. On the other hand there are alleles, which are not expressed on cell surface. In our laboratory both methods are established and the results of both were compared. It may be useful for determining the selection strategy of HLA-identical donor-recipient pair suitable for bone marrow transplantation. The results demonstrated 9% misassignments of HLA-A antigens by serology, 11% of HLA-B and 39% of HLA-C. The serological discrepancies found were of three categories: false negatives, false positives, and an incomplete typing. The vast majority of the discrepancies were due to a combination of relatively low expression of HLA antigens, lack of serological reagents and misclassification of antigens within cross-reactive groups. These results indicate that nowadays the serological typing is insufficient for clinical histocompatibility testing. (Tab. 3, Ref. 16.)

Alleles↗

Results of allogeneic bone marrow transplantation with unrelated or mismatched donors.

As most patients are not fortunate enough to have an HLA-matched sibling to use as a bone marrow donor, attention has focused on the use of either HLA-matched but unrelated donors or HLA-mismatched family members. With the maturation of the field of histocompatibility testing, it is now possible to quantitate with relative precision the degree of disparity between patient and donor. In general, it appears that with respect to histocompatibility differences between donors other than HLA-matched siblings, there is an increased incidence of acute graft-versus-host disease, with the risk correlated with the degree of histoincompatibility. However, the overall disease-free survival is not always adversely affected, as a graft-versus-leukemia effect may counterbalance the increased death rate from graft-versus-host disease. To find donors for most patients, efforts are under way to recruit a large number of unrelated volunteers into the National Marrow Donor Program.

Bone Marrow Transplantation↗

Two techniques to make the lymphocytotoxic crossmatch more sensitive: prolonged incubation and the antiglobulin test.

Two techniques capable of increasing the sensitivity of the lymphocytotoxic crossmatch test were compared for sensitivity and practically using the fluorochromasia modification of the cytotoxicity test. Prolonging the incubation period after addition of complement in the standard test resulted in further positive reactions. Modification of the test by addition of antiglobulin reagent increased the reactivity more than prolonged incubation of the standard test. The fluorochromasia adaptation of the antiglobulin test had sensitivity equivalent to the original antiglobulin method. The antiglobulin technique had a number of disadvantages, and neither the prolonged incubation nor the antiglobulin procedure meet the requirements of a busy histocompatibility testing service in view of the time consumed for the first and the complexity of the second.

Coombs Test↗

[SLA-testing and MCL-reaction in swine and their reaction to rejection of skin and liver transplants].

After porcine skin allografts there is a regular rejection within 6 - 12 days with a characteristic pattern of humoral antibodies corresponding to the histocompatibility testing. The rejection of skin allografts may be due to weak histocompatibility antigens which are not measured by the SL-A and MLC typing. A porcine liver allograft induces an immunological reaction of moderate degree. This state of hyporeactivity i. e. partial tolerance could be induced and maintained by the release of tolerogenic antigens from the porcine liver.

Animals↗

The relevance of proficiency testing for laboratories involved in cadaveric organ transplantation and its consequences for graft survival.

Organ exchange organizations such as Eurotransplant allocate organs on the basis of histocompatibility testing results. For this reason it is essential that all data reported by the affiliated laboratories are accurate and reliable. The Eurotransplant Reference Laboratory (ETRL) organizes proficiency testing schemes for the tissue-typing centers of the respective renal transplantation units participating in Eurotransplant. Each year, the ETRL sends out 8 peripheral blood samples of healthy blood donors for serological typing and crossmatching, 16 sera to screen for the presence and definition of HLA alloantibodies and 20 DNA samples for molecular typing to the 49 participating centers. The results are collected centrally and reported back to the participants in an open way. These exercises show that the quality of HLA typing, screening and crossmatching improved significantly over the years. In particular, the introduction of molecular typing for HLA-DR resulted in an increase of reliability. The clinical relevance of a reliable HLA typing was demonstrated in a selected group of transplants, the zero HLA-A,-B,-DR- mismatched group. After retyping the donors, 146 of the 3,458 matched transplants appeared to have a mismatch and those transplants had a significantly lower graft survival rate. A continuing problem, however, is the result of screening for panel reactive antibodies (PRA), where the percentage PRA reported for each serum varies significantly from center to center. The results indicate that the use of a PRA value for classification of patients and allocation of organs should be revisited.

Cadaver↗