Identification and Characterization of Anti-Platelet Antibodies in Idiopathic Thrombocytopenic Purpura Patients

BACKGROUND The autoimmune disease known as Idiopathic (immune thrombocytopenic purpura thrombocytopenic purpura (ITP) is clinically defined by a low numbers of platelets in the circulation blood. This study aimed to isolate autoantibodies made against the platelet glycoproteins using platelets from healthy volunteers, to determine their specificity and further elucidate their effects on platelet function. METHODS This study used a phage display system to recognize Fab anti-platelet antibodies. Anti-platelet After isolation, the anti-platelet Fab-expressing phage was characterized by ELISA and Western blotting. The Fab-bearing phage pool obtained from five rounds of panning was analysed in order to determine its anti-platelet reactivity. Of the phage colonies obtained, 100 colonies of different sizes were randomly selected for reaction with whole platelets, using M13 phage as a negative control. RESULTS Twelve colonies of them had strong reactions against the whole platelet preparation, but only four colonies showed substantial reactivity against the lysed platelet preparation (lysate). Three of the four colonies showed three bands representing proteins with different molecular weights. The fourth colony showed only a single band. The final experiment to characterise the protein isolated from the phage library was a DNA gel agarose test. CONCLUSION Each colony showed a DNA band that corresponded with the molecular size marker for 5.4 kbase pairs, and this suggested the presence of heavy and light antibody chains in the phage.