Tuesday, January 21, 2014

Antibodies, Bioassays, and Cells: The ABCs of Immunochemistry

Today, Cheryl Scott of BioProcess International takes us on a brief history of the ABCs of Immunochemistry.

A Brief History
At its most basic, immunochemistry is the branch of chemistry that covers how our immune systems react to and make use of the biomolecules listed above. One of the earliest examples was the Wasserman antibody test for detection of syphilis. It was developed by August Paul von Wassermann, Julius Citron, and Albert Neisser at Germany’s Robert Koch Institute for Infectious Diseases in 1906. Based on a complement-fixation serological reaction, this test grew out of earlier work performed in Belgium. The reaction is not specific to syphilis (other diseases such as malaria and tuberculosis also cause a positive response), and some infected persons produce no reaction whereas successfully treated patients can continue to show a reaction. So even though it’s been refined over time, the Wassermann test is rarely used today. Other early complement-fixation methods have also been replaced by serological methods such as enzyme-linked immunosorbent assays (ELISAs) and DNA-based methods of pathogen detection such as polymerase chain reaction (PCR).

Another pioneer in immunochemistry was Svante Arrhenius, a Swedish physicist whose work in chemistry brought the two disciplines together in what is now known as the study of physical chemistry. Arrhenius published a book called Immunochemistry in 1907 describing the application of physical chemistry methods to the study of toxins and antitoxins. Some immunochemists use antibodies to label epitopes of interest in cells (immunocytochemistry, ICC) or tissues (IHC, immunohistochemistry).

ICC uses antibodies to target specific peptides or protein antigens in cells through their specific epitopes. Bound antibodies are detected using a number of technologies such as f luorescent tagging, chromogenic staining, and secondary antibodies. For example, immunof luorescence is combined with confocal microscopy for studying the location of proteins and dynamic processes in cells — something for which Invitrogen’s Molecular Probes division of Eugene, OR, is well known. ICC allows researchers to evaluate whether particular cells express a specific biomolecule and shows them which subcellular compartments are expressing it. Similarly IHC methods detect antigens in tissue sections.

Immunohistochemical staining is widely used in diagnosis of abnormal (e.g., cancerous) cells. Certain molecular markers are characteristic of cellular events such as proliferation or apoptosis. IHC helps researchers understand the distribution and localization of biomarkers and differentially expressed proteins in tissues.

To look deeper into these applications, download the read the full article here.

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