Genetic aspects of the blood transfusion effect

Development and evaluation of a transfusion medicine genome wide genotyping array

BACKGROUND

Many aspects of transfusion medicine are affected by genetics. Current single-nucleotide polymorphism (SNP) arrays are limited in the number of targets that can be interrogated and cannot detect all variation of interest. We designed a transfusion medicine array (TM-Array) for study of both common and rare transfusion-relevant variations in genetically diverse donor and recipient populations.

STUDY DESIGN AND METHODS

The array was designed by conducting extensive bioinformatics mining and consulting experts to identify genes and genetic variation related to a wide range of transfusion medicine clinical relevant and research-related topics. Copy number polymorphisms were added in the alpha globin, beta globin, and Rh gene clusters.

RESULTS

The final array contains approximately 879,000 SNP and copy number polymorphism markers. Over 99% of SNPs were called reliably. Technical replication showed the array to be robust and reproducible, with an error rate less than 0.03%. The array also had a very low Mendelian error rate (average parent-child trio accuracy of 0.9997). Blood group results were in concordance with serology testing results, and the array accurately identifies rare variants (minor allele frequency of 0.5%). The array achieved high genome-wide imputation coverage for African-American (97.5%), Hispanic (96.1%), East Asian (94.6%), and white (96.1%) genomes at a minor allele frequency of 5%.

CONCLUSIONS

A custom array for transfusion medicine research has been designed and evaluated. It gives wide coverage and accurate identification of rare SNPs in diverse populations. The TM-Array will be useful for future genetic studies in the diverse fields of transfusion medicine research.

Critical Requirement for Graft Passenger Leukocytes in Allograft Tolerance Induced by Donor Blood Transfusion

Tolerance to a vascularized allograft can be induced in adult animals by pregraft donor-specific blood transfusion (DST). Mechanisms underlying this effect appear to depend on unresponsiveness of alloreactive T-helper cells. In this study, we examined the roles of DST and cellular components of the allograft that are important in inducing T-cell unresponsiveness in a rat model. DST alone did not tolerize alloreactive recipient T-helper cells, but the combination of DST and heart allograft induced profound inhibition of the antidonor proliferative response in spleen but not in lymph node cells. When heart allografts were depleted of passenger leukocytes by pretreating the donor with cyclophosphamide or by parking the graft for 2 months in a tolerant recipient, tolerance induction in DST-treated recipients was abrogated. Tolerance could then be restored in a majority of DST-treated recipients of passenger leukocytes depleted grafts by injecting them at the time of grafting with donor, but not third-party, dendritic cells. This indicates that graft passenger leukocytes, most likely dendritic cells, are required for DST-induced allograft tolerance.

Critical Requirement for Graft Passenger Leukocytes in Allograft Tolerance Induced by Donor Blood Transfusion

Tolerance to a vascularized allograft can be induced in adult animals by pregraft donor-specific blood transfusion (DST). Mechanisms underlying this effect appear to depend on unresponsiveness of alloreactive T-helper cells. In this study, we examined the roles of DST and cellular components of the allograft that are important in inducing T-cell unresponsiveness in a rat model. DST alone did not tolerize alloreactive recipient T-helper cells, but the combination of DST and heart allograft induced profound inhibition of the antidonor proliferative response in spleen but not in lymph node cells. When heart allografts were depleted of passenger leukocytes by pretreating the donor with cyclophosphamide or by parking the graft for 2 months in a tolerant recipient, tolerance induction in DST-treated recipients was abrogated. Tolerance could then be restored in a majority of DST-treated recipients of passenger leukocytes depleted grafts by injecting them at the time of grafting with donor, but not third-party, dendritic cells. This indicates that graft passenger leukocytes, most likely dendritic cells, are required for DST-induced allograft tolerance.

Semi-allogeneic (F1) versus fully allogeneic blood transfusions: differences in their ability to induce specific immunological unresponsiveness

The beneficial effect on graft survival achieved by pretransplant blood transfusions is well established. However, the type of major histocompatibility complex (MHC) mismatch between transfusion donor and recipient seems to play a role in determining the outcome. The hypothesis that this sharing of MHC antigens is correlated with the level of sensitization or tolerization was studied in mice by pretreatment with semi-allogeneic (F1) or with fully allogeneic whole blood transfusions. Limiting dilution analysis (LDA) in vitro for donor-specific T helper (Thp) and cytotoxic T lymphocyte precursors (CTLp) performed on splenocytes isolated from transfused recipients 2 or 4 weeks after transfusion showed that the duration and magnitude of the response was reduced after a semi-allogeneic compared to a fully allogeneic transfusion. After a semi-allogeneic transfusion, both Thp and CTLp frequencies had returned to naive levels 4 weeks after transfusion, whereas after infusion of fully allogeneic blood, they remained elevated after 4 weeks. When a fully allogeneic heart was transplanted 2 or 4 weeks after transfusion, a small but significant improvement in graft prolongation (2 weeks, not significant, 4 weeks: p < 0.01) was observed following pretreatment with a semi-allogeneic transfusion (2 weeks: median survival time (MST) 30 days, 4 weeks: MST 29 days) compared to that obtained after fully allogeneic transfusion (2 weeks: MST 23 days, 4 weeks: MST 12 days). The semi-allogeneic transfusions were correlated with a statistically significant prolonged (7 days) persistence of donor-derived MHC class II+ cells in the recipient and with reduced levels of anti-donor MHC class I-specific antibody formation compared to these responses after transfusion with fully allogeneic cells. These results demonstrate that pretreatment with a semi-allogeneic blood transfusion is more tolerizing and less sensitizing than pretreatment with a fully allogeneic blood transfusion. These findings may be explained by the sharing of MHC antigens between recipient and transfusion donor.

Expression of granzyme A and perforin in mouse heart transplants immunosuppressed with donor-specific transfusion and anti-CD4 monoclonal antibody

Granzyme A and perforin are produced by activated cytotoxic T lymphocytes and their expression correlates with the appearance of cytotoxicity. Using in situ hybridization and immunohistochemistry, we examined the phenotype of cellular infiltration and the appearance of granzyme A+ and perforin+ cells in a mouse cardiac transplant model where the recipients were pretreated with donor-specific transfusion, anti-CD4 monoclonal antibody, or both. While the profiles of cellular infiltration failed to correlate with graft survival, tolerized grafts, as compared with untreated allografts, showed a decreased frequency of granzyme A and perforin expression. These functional markers of cytotoxic T lymphocytes can differentiate between rejecting and indefinitely surviving grafts and may be of value in dissecting the immunological events involved in tolerance induction.

The blood transfusion effect: experimental aspects

In some animal models of organ transplantation, notably the rat, preoperative administration of donor strain blood may produce long-term allograft survival even in the absence of adjunctive immunosuppressive therapy. The ability of blood transfusion to prevent rejection is highly dependent on the strain combination and type of graft, as well as the nature, dose and timing of transfusion. Although the effect is donor-specific, partial sharing of MHC and/or minor antigens between the blood and organ donor may be sufficient to prolong graft survival. The mechanisms underlying the enhancing effect of blood transfusion and other protocols which lead to specific unresponsiveness in the adult animal are undoubtedly complex and still poorly understood. In contrast to neonatal tolerance, where there is complete clonal deletion or anergy, lymphocytes from enhanced animals often show normal alloreactivity in vitro. Blood transfusion provokes an accelerated immune response to an allograft with rapid leukocyte infiltration of the graft and associated induction of class I and class II MHC target antigens. Moreover, graft infiltrating cells obtained from non-rejecting grafts in transfused recipients show levels of in vitro specific cytotoxicity equivalent to or in excess of those found in rejecting grafts. Despite the heightened cellular response provoked by blood transfusion, host regulatory mechanisms override the rejection response and there is substantial evidence for the existence in transfused animals of T cells with antigen specific suppressor activity. However, the site in the rejection process at which suppression is mediated is unknown.(ABSTRACT TRUNCATED AT 250 WORDS)