Documented allergy to DMSO, mouse or bovine proteins, or iron. Known allergy or intolerance to any component of belimumab, including human or murine proteins or monoclonal antibodies History of allergy to mouse proteins Known allergy to murine proteins or have had a documented anaphylactic reaction to any drug, or a known hypersensitivity to diphenhydramine or other antihistamines of similar chemical structure. History of allergy to mouse proteins History of allergy to mouse proteins Patients who are known to have allergy to mouse proteins History of allergy to mouse proteins History of allergy to mouse proteins History of prior ? grade hypersensitivity reaction or any toxicity attributed to trastuzumab or murine proteins that warranted permanent cessation of these agents (applicable for Cohort only). Allergies or hypersensitivity to murine, chimeric, human or humanised proteins History of severe environmental allergies or allergy to egg proteins History of allergy to egg proteins hypersensitivity to trastuzumab, murine proteins, fulvestrant, or to any of the excipients History of allergy to murine proteins History of allergy to murine proteins History of allergy to mouse proteins Known hypersensitivity to murine or chimeric antibodies or proteins History of intolerance (including grade or infusion reactions) to murine proteins History of intolerance, including Grade to infusion reaction or hypersensitivity to trastuzumab or murine proteins or any components of the product Patients with known hypersensitivity to mouse proteins (murine antibodies in ISOLEX) if receiving soybean agglutinin and E-rosetting (SBA-E) bone marrow, or chicken egg products Patients with known hypersensitivity to mouse proteins (murine antibodies in ISOLEX) if receiving T-cell depleted (soybean lectin agglutination [SBA]-E)- bone marrow, or chicken egg products History of severe environmental allergies or allergy to egg proteins No prior history of intolerance or hypersensitivity to trastuzumab and/or adverse events related to trastuzumab, murine proteins, or any of the excipients that resulted in trastuzumab being permanently discontinued Type I hypersensitivity or anaphylactic reactions to murine proteins or to previous infusion of rituximab History of intolerance (including grade or infusion reaction) or hypersensitivity to trastuzumab or murine proteins Prior history of hypersensitivity to milk proteins Patients with a history of allergy to human proteins Documented allergy to iron dextran or murine proteins Prior exposure to murine proteins or chimeric antibodies