What Are Antibodies?

We often discuss the importance of viscosity measurements of antibodies and other biotherapeutics, but what exactly are antibodies? 

An antibody, also known as an immunoglobulin, is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the pathogen, called an antigen (or antibody stimulator). Antibodies are made of four polypeptides produced by the plasma cells. More simply put, antibodies are "protective proteins produced by your immune system that remove foreign substances from your body". (Cleveland Clinic). 

Antibodies are categorized into 5 classes based on their location in your body:

• IgA antibodies are  found in saliva, tears, mucus, breast milk and intestinal fluid, and protect against ingested and inhaled pathogens
• IgD are antibodies found on the surface of your B cells (white blood cells), and are thought to support B cell activation when fighting infection
• IgE  antibodies are found in the skin, lungs and mucus membranes, and are known for triggering allergic reactions 
• IgG  antibodies are found in blood and tissue fluids and help protect against viral and bacterial infections. IgG antibodies make up ~70 - 75% of all antibodies in your body
• IgM  antibodies are found in your blood and lymph system, and act as the first line of defense against infection

Monoclonal antibodies (mAbs) are man-made proteins (made in a lab), designed to mimic your immune system’s natural ability to fight off pathogens.  Monoclonal antibody therapy is a form of immunotherapy that uses monoclonal antibodies (mAb) to bind monospecifically (targeting the same antigen) to certain cells or proteins, which if successful will stimulate the patient's immune system to attack those cells. mAbs have promising applications in the treatment of different diseases, including cancer, autoimmune diseases, numerous infectious diseases and even Alzheimer’s disease. Since 1985, approximately 100 monoclonal antibodies have been designated as drugs (Manis et. al).

The desirable properties for the target mAb products include stability, compatibility, syringeability, and injectability. Exploring viscosity of mAbs over a broad range of shear rates to identify non-Newtonian behavior can be crucial to predicting all aspects of performance of these high concentration injectable solutions, including stability and delivery.

Download our application note “Are concentrated monoclonal antibody formulations Newtonian?” to learn more about the importance of measuring viscosity of mAbs over a broad range of shear rates to determine if, and when, non-Newtonian behavior is observed. 

Written by: Eden Reid, RheoSense Senior Marketing and Sales Operations