Western blot An immunochemical method for identifying proteins in a complex mixture, proteins separated by electrophoresis are transferred (blotted) from the gel medium to a protein-binding nitrocellulose or polymeric membrane; the transferred proteins are then detected by their relative binding to labeled antibodies. (See blotting)

WFI Water for injection; very pure water that meets specifications defined by the USP or other compendia; suitable for parenteral uses.

withdrawal Product withdrawal; a recall of a lot of product that is done voluntarily by a firm, when there is concern about product quality that is not proven. A recall may be mandated by FDA or regulatory bodies. (See also recall)

working cell bank A cell bank that is usually made from a single vial of the master cell bank, in which each vial has comparable contents and is expected to perform consistently when introduced into a process or assay. Both master and working cell banks are extensively tested and characterized before use. Manufacturing usually starts when a vial of working cell bank is thawed and added to a reactor. (See master cell bank)

xenotransplantation Implantation of living cells, tissues, or solid organs from one species into another, used when human donors are unavailable or when a temporary or "bridge" organ is needed; a controversial practice given concerns about potential viral transmission and strong immunological reactions.

YAC Yeast artificial chromosome; a vector used to clone DNA fragments up to 100,000 base-pairs long. YACs are constructed from the telomeric, centromeric, and replication sequences of yeast cells.

yeast A single-celled fungus (eukaryote).

Waters, UltraPerformance Liquid Chromatography, and UPLC are registered trademarks of Waters Corporation. BiopharmaLynx, HDMS, High Definition Mass Spectrometry, MassLynx, SYNAPT, and The Science of What's Possible are trademarks of Waters Corporation.

Following acronyms that appear in brackets throughout the guide represent the sources of definitions :

FDAQSG definition is the one that appears in the US FDA's Quality Systems guidance.

ICH Q6B definition is the one that appears in the International Conference on Harmonization (ICH) Q6B guideline, "Test Procedures and Acceptance Criteria for Biotechnological/Biological Products"

ICH Q8 definition is the one that appears in the ICH Q8 guideline, "Pharmaceutical Development."

ICH Q9 definition is the one that appears in the lCH Q9 guideline, "Quality Risk Management."

ISO 14971 Refers to the International Organization for Standardization's standard 14971, "Medical Devices—Application of risk management to medical devices."

ISO/IEC Guide 51 Refers to the joint ISO and IEC {International Electrotechnical Commission) publication, "Safety aspects—Guidelines for their inclusion in standards."

ISO Guide 73 Refers to ISO Guide 73, "Risk management—Vocabulary—Guidelines for their use in standards."