Intravenous immunoglobulin (IVIG) therapy is used to provide passive immunity or to alter the immune response by increasing an individual's antibody titer and antigen-antibody reaction potential. IVIG has been investigated as a treatment for patients who are infected with human immunodeficiency virus (HIV) and who suffer from recurrent bacterial infections, severe HIV-related thrombocytopenia, and chronic parvovirus B19 infections.