The present invention relates to the treatment of immune system abnormalities that can be found in lethal human cancers and also in the progressive Human Immunodeficiency Virus Type 1 (HIV-1) infections and provides medicaments to correct abnormalities in a subject with cancer or HIV-1-infected subjects, in order to allow the immune system to fight the cancer or HIV-1 infections. The present invention also discloses multivalent polypeptides which specifically bind to and enable destruction and/or inactivation of immune cells that have CD11b and CD3 on their surface, therefore dissipating the deleterious effects of the CD11b+T cells.