ABSTRACT
BACKGROUND: The development of symptomatic or asymptomatic thrombocytopenia is not uncommon in HIV seropositive drug addicts. METHODS: Platelet binding immunoglobulins, as immune complexes or as platelet specific antibodies, were studied in eleven patients. Whole sera anche serum factions obtained by PEG sedimentation and gel filtration were investigated using methods able to characterize the IgG and IgM immunoglobulin classes. Immune complexes-containing fractions were used in competition assays with some monoclonal antibodies with receptor specificities. RESULTS: Immune complexes able to bind both autologous and allogenic platelets were detected in all patients, while platelet specific IgG or IgM autoantibodies were detected in most, but not in all, patients. The results obtained with the various individual tests were sometimes discrepant, owing to the low avidity binding of platelet-reacting immunoglobulins. Anti-low-affinity FcRII monoclonal antibody moderately reduced the platelet binding of IgG containing immune-complex fractions. CONCLUSIONS: In thrombocytopenic, HIV seropositive drug addicts immunecomplexes and platelet specific antibodies usually coexist and possibly have different pathogenetic potential in the development of thrombocytopenia.
