Antibodies are proteins that function within the immune system to identify or attack pathogens in the body. Antibodies bind to antigens present on the surface of foreign cells, and either neutralize the pathogens directly or tag them for other elements of the immune system to destroy.
An antibody, or immunoglobulin [Ig], features a “Y” shaped structure with an antigen-binding site called a paratope located at the end of each arm. These paratopes bind to structures called epitopes on the surface of hostile antigens as they circulate through the body. Antigen epitopes fit into corresponding antibody paratops like a key into a lock, and the antibody-antigen reaction is highly selective—a given antibody is capable of binding to only one specific antigen.
The antibody-antigen reaction can defuse threats from hostile cells directly if binding a pathogen’s antigens to antibodies prevents the pathogen from invading healthy cells or replicating within the body. For example, certain antibodies bind to toxins and change their chemical composition to neutralize the poison—these antibodies are called “antitoxins.” Likewise, certain antibodies can immobilize harmful microorganisms or disrupt their cellular membranes, triggering lysis in the invaders.
In other cases, the antibody-antigen reaction serves as a flag to alert the immune system to attack the microorganisms to which antibodies are bound. In this way, white blood cells or other macrophages know to target and kill foreign cells that are tagged with antibodies.
Antibodies are produced by B cells, which are a vital component of the immune system. B cells feature several antigen receptors on their surface, which are comprised of Ig proteins anchored to the membrane of the B cell.
When antigens bind to B cell receptor [BCR] antibodies, the antibody-antigen reaction stimulates the B cells to produce and secrete antibodies with paratopes that match with the epitopes on the antigen that activated the B cell in question. These free antibodies then circulate throughout the immune system, binding to their corresponding antigens to tag or neutralize harmful pathogens. In this way, antigens induce production of antibodies in B cells when they bind to Ig proteins in the BCRs.
The BCRs covering the surface of a given B cell feature antibodies with identical chemical compositions. The exclusivity of the antibody-antigen reaction thus requires that a given B cell can recognize and bind to only one specific antigen epitope structure and produce antibodies with only one specific paratope structure. As such, the immune system relies on a diversity of B cells to respond to the different antigens that may be present in the body—particular antigens trigger particular B cells to produce specific antibodies that are uniquely suited to bind to the antigens in question.
Antigens are also present on the surface of healthy cells that are native to the body. In order to prevent these native antigens from binding to immune system antibodies, or stimulating B cell antibody production against these native antigens, developing B cells undergo a process called central tolerance. Also called “negative selection,” central tolerance eliminates B cells that exhibit self-reactive qualities, so that only B cells that react to foreign or hostile pathogens reach antibody-producing maturity.
Studying antibodies and leveraging the antibody-antigen reaction is a critical component of immunological research. Scientists can introduce antibodies to a patient to neutralize or identify and tag the antigens present on the surface of pathogens. In kind, introducing antigen proteins or weakened pathogens can stimulate a patient’s B cells to produce antibodies that correspond to the specific antigens present on the pathogen in question.
Whether derived from blood samples of previously infected hosts or produced through genetic engineering, antibodies or antigens deployed in treatment or vaccination rely on the same antibody production steps as these which naturally occur within the body when the immune system encounters a foreign pathogen. Antibody treatment has numerous applications, from vaccination to cancer cell destruction or protecting T cells from being disrupted by disease.
As B cells are the lynchpin of antibody production within a patient, isolating viable B cells from a patient is essential to being able to analyze how they will react to treatment that stimulates the production of the specific antibodies needed to combat a given pathogen. Since the presence of other cell types may interfere with the accuracy of analysis or disrupt the antibody production of B cells, it is important that the isolated B cell population is pure (high proportion of B cells to unwanted cells) and viable (healthy, functioning B cells). B cells are typically isolated from a biological sample by looking for identifying markers on the cellular surface and separating cells that exhibit these markers from unwanted cells in the sample.
Traditional procedures for B cell separation involve fluorescence-activated cell sorting [FACS], density gradient centrifugation, magnetic-activated cell sorting [MACS], filtration, or aptamer-based cell isolation. These technologies are often cost- and time-prohibitive, as they require assortments of complex equipment and extensive training to perform. Moreover, these common approaches often retain unwanted cells in the isolated population, impeding the purity, viability, and function of the isolated sample.
Buoyancy-Activated Cell Sorting [BACS] technology from Akadeum Life Sciences offers a compelling alternative to industry-standard B cell isolation protocols that is gentle, accurate, and efficient.
The BACS procedure first labels unwanted cells within a sample with biotinylated antibodies. Then, streptavidin-coated microbubbles are mixed into the sample. The streptavidin on the microbubbles binds with the biotinylated antibody bound to the antigen on the unwanted cells, and the buoyant microbubbles and their captured unwanted cells then float to the surface of the sample for removal, leaving a pure population of healthy, unaltered cells behind for downstream applications.
B cells can easily be isolated from a heterogenous biological sample using BACS microbubble technology. Akadeum’s microbubbles exploit the exclusivity of the antibody-antigen reaction to target and bind to only the unwanted cells that have been labeled with specific antibodies. Because the antibodies in the BCR receptors on the surface of B cells can only react with certain antigen proteins, they do not bind to the streptavidin protein microbubbles or become activated prematurely. Instead, the B cells in the population remain at the bottom of the sample once the unwanted cells are floated to the surface.
Akadeum’s BACS products are affordable, easy-to-use, and require no specialized equipment or training. Microbubble cell sorting opens the door for small labs and research institutions alike to conduct B cell sorting quickly, at commercial scale, while preserving the integrity of the B cells essential for immunological study. Take a look at our B cell isolation products and use our precise antigen-antibody binding microbubbles for high accuracy B cell separation.