Complement (C1q) Binding to HLA Antibodies in a Solid-phase Immunoassay and Clinical Effect on Platelet Transfusion

Background: Platelets are blood cells that help blood clot. Some people have what is called thrombocytopenia. This means they have a low blood platelet count. They need platelet transfusions very often. Human leukocyte antigen (HLA) alloimmunization occurs for a lot of these people. They become refractory. This means their platelet levels no longer increase after transfusions. Researchers want to study a procedure that detects HLA antibodies. They want to test how well it predicts how a person will respond to a transfusion. They want to see if it does this better than the procedure that is usually used. Objective: To study the effect of C1q-binding of Class I HLA antibodies on platelet refractoriness in people who get platelet transfusions. To test if this method better predicts response to platelet transfusion than the IgG solid phase immunoassay method. Eligibility: People enrolled on protocols 11-C-0136, 08-H-0156, 03-C-0277, 01-C-0157, or 01-C-0129 who: Agreed to have their specimens and data used for future research Had Class I HLA antibodies detected by the IgG method Had one or more platelet transfusions at NIH after the first positive HLA IgG antibody result Design: For each participant, researchers will look at a small portion of their archived plasma sample. The samples were left over from prior HLA antibody tests. Participants samples will be analyzed. They will be tested to see if C1q-binding HLA antibodies are present. This will be done by solid phase immunoassay. Results will be compared with the past results of the IgG method. Participants data will be stored in database that s protected by password. ...