The role of neutrophil primining and neutrophil antibodies in the pathogenesis of Transfusion-Related Acute Lung Injury (TRALI)

Yoke Lin Fung (2008). The role of neutrophil primining and neutrophil antibodies in the pathogenesis of Transfusion-Related Acute Lung Injury (TRALI) PhD Thesis, School of Medicine, The University of Queensland.

       
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Author Yoke Lin Fung
Thesis Title The role of neutrophil primining and neutrophil antibodies in the pathogenesis of Transfusion-Related Acute Lung Injury (TRALI)
School, Centre or Institute School of Medicine
Institution The University of Queensland
Publication date 2008-06
Thesis type PhD Thesis
Supervisor Dr Peter Wood
Dr Robyn Minchinton
Total pages 216
Total colour pages 15
Total black and white pages 201
Subjects 320000 Medical and Health Sciences
Formatted abstract Transfusion-related acute lung injury (TRALI) is a serious and potentially fatal complication of blood transfusion. Clinically, TRALI can occur in both adults and children without warning and is identical to acute respiratory distress syndrome (ARDS). The main difference is the association of TRALI with a recent blood transfusion.
Lack of complete understanding of the pathogenesis of TRALI, prevents the blood transfusion world from developing and implementing effective strategies to reduce the incidence of this serious transfusion complication.
In 2003, when this work began, only the Immune Mechanism and the Two-Hit Mechanism for TRALI had been proposed. While the detection of leucocyte antibodies in transfused blood products supported the Immune Mechanism, there was little information about the antibodies mechanism of action in TRALI patients. The Two-Hit Mechanism proposed a central role for primed patient neutrophils (PMNs) in TRALI, but information about the functional phenotype of these PMNs was limited. To address these knowledge gaps, work for this thesis focussed on the role of PMN priming and PMN antibodies in the pathogenesis of TRALI.
This first publication described the detailed laboratory investigation of two cases of childhood TRALI. This report was intended to increase awareness of TRALI in children. The literature review of TRALI in childhood made prominent the abnormally high morbidity associated with this transfusion complication in the young, and the paper detailed the “state of the art” of serological investigations recommended for TRALI then.
To investigate of the role of PMN priming in the pathogenesis of TRALI, we asked the question “Do ill patients have primed PMNs which increases their susceptibility to TRALI?” The PMN respiratory burst assay was validated and used to differentiate between the three PMN functional phenotypes (quiescent, primed and activated). PMN surface expression of functional
antigens, CD43, CD16, CD62L, CD11b and CD18 was quantified concurrently. Normal ranges for these assays were established using the PMNs of 100 healthy blood donors to facilitate reliable comparison with two planned patient cohorts.
The second publication described a cohort of 110 patients with systemic inflammatory response syndrome (SIRS) who represented a diverse population of very ill individuals. Notably, the respiratory burst assay data, demonstrated that the circulating PMNs from these SIRS patients were neither primed nor activated. Furthermore, changes to the surface molecules on the circulating PMNs revealed a predominantly hypo-responsive phenotype. Therefore, in contrast to the hypothesis proposed in this thesis, these results indicated that SIRS patients with significant systemic inflammation did not have increased susceptibility to TRALI as a result of circulating, primed PMNs.
To determine whether a different clinical insult was required to generate primed circulating PMNs, we longitudinally studied PMNs from 20 elective cardio-pulmonary bypass (CPB) patients using the same investigation profile. This cohort was selected because primed circulating PMNs have been reported following cardiac surgery and cardiac patients have been connected with a higher risk of TRALI. During the post-CPB neutrophilia the PMNs were neither primed nor activated. Instead, primeability was reduced and continued to decline. PMN surface molecules presented a hypo-responsive phenotype and may have indicated a homeostatic response to avoid injury to self. The PMN phenotype and primeability data indicated that CPB patients did not have a higher risk of TRALI 1 - 5 days post-CPB.
To investigate the involvement of PMN antibodies in TRALI, serum from a TRALI implicated blood donor with anti-HNA-2a specificity was investigated serologically, for its affect on PMN surface molecule expression and on the PMN’s respiratory burst. The serum did not prime HNA-2a+ PMNs, nor alter their respiratory burst but did increase PMN integrin expression. These findings did not support a role for the antibody in priming or activating PMNs
in TRALI. The anti-HNA-2a serum caused PMN agglutination. It’s binding to HNA-2a+ PMNs effectively blocked the subsequent binding of two CD177 monoclonal antibody clones. These findings highlighted the polyclonality and diverse epitope specificity of this donor TRALI antibody compared with monoclonal antibodies to the same antigen. This antibody profile might signify donor antibodies which might be most likely to precipitate TRALI. Further epitope mapping of the targets of TRALI antibodies and comparison with non-TRALI sera of the same antigenic specificity (e.g. from immune neutropenia) could support this hypothesis.
Over all, this work found evidence to disprove the thesis’ hypothesis. The expression of various functional surface PMN antigens was not revealed as a convenient metric to indicate the primed or activated PMN state. Results from the clinical studies provided novel and substantial evidence that patients with systemic inflammation, and post-CPB surgery did not have primed circulating PMNs, thereby challenging the initial step proposed in the Two-Hit TRALI Mechanism. Further work is now required to determine whether a substrate of primed PMNs is trapped in the pulmonary microvasculature of TRALI susceptible patients. Instead, the data from this thesis appears to provide stronger support for the proposed Threshold Mechanism of TRALI.
Keyword TRALI, neutrophil, phenotype, respiratory burst, prime, activate, transfusion, neutrophil antibody, cross-match, lung injury
Additional Notes 18,20,24,26,29,31,35-38,46,61,67,68,71

 
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