Immunology of allosensitization observed with left ventricular assist device implantation: can newly developed methods define precise antibody specificities?

Patients implanted with left ventricular assist devices (LVAD) often develop lymphocyte reactive antibodies (allosensitization) leading to prolonged waiting time and possible poor transplant outcome. The question is: are these antibodies specifically directed against HLA class I antigens and what may be causing their induction? This thesis is intended to define more precisely the specificity of the lymphocyte reactive antibodies and to evaluate newly developed methods to define allosensitization. Sera from sensitized LVAD recipients studied for autoimmune antibodies and underwent a series of differential cellular adsorptions and elutions. Sera (unabsorbed and absorbed) and eluates were assayed in parallel using newly developed methods to define antibody specificities. Fifteen patients were studied in this investigation. Antiphospholipid antibodies were detected in seven of seven patients tested, but only four of the seven remained positive as HLA specific antibodies became apparent. No patients tested positive for autoantibodies against antinuclear antigens. No auto- or cross-reactivity to pig lylmphocytes was found by differential cellular absorptions, and the thermal optima of antibody binding were consistent with alloreactivity. Sera from eight patients absorbed with pooled platelets had a 78% reduction in reactivity to class I HLA antigens. Preliminary specificity assignments were confirmed in six of eight patients as a result of absorption using homozygous B-cells. Using a newly developed single HLA class I antigen flow method, HLA specificity was determined in seven of seven patients previously reported as multispecific. Blocking studies confirmed HLA class I specificity in six of six patients. Only three of twelve patients tested positive for proinflammatory or immune-stimulating cytokines. This investigation demonstrates that a majority of sensitized LVAD recipients have IgG antibodies that are optimally active at room temperature and 37°C, have high avidity, and show HLA specificity in the absence of auto- and cross-reactivity. Also the use of singly HLA antigen coupled heads to test high panel reactive antibody (PRA) sera showed the precise information about antibody specificity could be obtained. Blood transfusion, chronic infection, and the LVAD itself are the most likely the causes of allosensitization.