Leukocyte Functions

What Is a Leukocyte?

Leukocyte is another name for white blood cells. Unlike red blood cells, leukocytes do not contain hemoglobin and they have a nucleus that inhibits their malleability. Due to variability in internal structure and organelles, leukocytes come in a variety of shapes and sizes specific to their unique functions. 

Leukocytes play a primary role in disease and infection defense. White blood cells (WBCs) either directly attack or aid other cells during immune responses—destroying foreign materials, infectious agents, and even cancer cells. In addition to combating infection head-on, some leukocytes produce antibodies that circulate through the bloodstream. 

Early stages of leukocyte development occur in the bone marrow. They circulate through the bloodstream and lymphatic vessels or reside in the secondary lymphoid organs, where they await activation. Allergic reactions or other immune responses spur leukocytes to traffic to infected areas, repair damaged tissue, or kill cancer cells. 

Because WBCs have a short lifespan, our bodies constantly produce them. Most people will produce 100 billion WBCs every day. A patient’s leukocyte cell count can indicate health status and risk of disease or infection. 

Leukocytes are integral to fighting infection and preventing disease; they come in many subtypes each with a unique function.  Some leukocytes do not directly kill pathogens or foreign cells, but rather aid and assist other leukocytes to help effectively eliminate the threat. 

Types of Leukocytes

Leukocytes are divided into granulocytes and agranulocytes. Each type of granulocyte and agranulocyte plays a distinct role in fighting infection and disease. 

Granulocytes contain granules or sacs and are the first line of the immune system’s defense. Neutrophils, eosinophils, and basophils are all considered granulocytes.  The concentration of granulocytes increases in response to infection, assisting in detection of disease, and providing the body’s innate immune response. Innate immune responses are immediate and non-specific, providing a broad range of protection against infection and aiding in the identification of non-self antigens. 

Granulocytes and agranulocytes, non-granule containing immune cells,  are commonly separated during cell studies, as they function differently in our bodies’ immune response. Agranulocytes are made up of monocytes and lymphocytes, or PBMCs (peripheral blood mononuclear cells).  Mononuclear leukocytes have unique capabilities that play an integral role in keeping your body healthy and building adaptive immunity (also called specific immunity). 

Monocytes are macrophages that engulf pathogens while lymphocytes can be divided into the following:  T cells, B cells, NK cells, and some subsets of dendritic cells. Although granulocytes and agranulocytes are associated with innate and adaptive immunity respectively, they can aid in both types of immune response. 

Neutrophils

Neutrophils are highly abundant granulocytes that serve as the immune system’s first responders. They defend against bacterial or fungal pathogens, as well as minor inflammatory responses. As they attack and die in mass quantities, their accumulation at the site of infection can lead to liquefactive necrosis—commonly known as pus. 

Neutrophils are very powerful bacteria destroyers, as they are chemically drawn to bacterial cells. They have phagocytic capabilities, meaning they are capable of engulfing target cells and, aided by their granules, destroying them via phagocytosis.

Basophils

Basophils aid in the short-term immune response by rapidly releasing enzymes and chemicals upon recognizing pathogens. By secreting histamines, basophils promote inflammatory responses and can inhibit blood clotting by opening capillaries to allow faster transit of other leukocytes. Basophils are the least common type of leukocytes.

Eosinophils

Most active in parasitic and allergic responses, eosinophils destroy parasites by phagocytosis. By quickly moving to the infection site, they trap infections and kill cells or parasites. Eosinophils can increase inflammation, which is a necessary aspect of the immune response; however, an overly aggressive  inflammatory response can pose risk of tissue damage.

Monocytes

Macrophages and some dendritic cells are subgroups of monocytes, capable of engulfing and breaking down foreign particles. They perform phagocytosis and antigen presentation to T cells. They aid in informing lymphocytes of infection and stimulate a more active immune response. Some monocytes develop into macrophages and migrate between blood and tissue, patrolling  tissues to remove dead neutrophils, cellular debris, and remaining pathogens after a first-wave immune response. 

Lymphocytes

There are three types of lymphocytes: B lymphocytes, T lymphocytes, and natural killer cells—or NK cells. B and T cells make up the majority of lymphocytes. B lymphocytes produce antibodies that are used to attack specific invading bacterias, viruses, or toxins. Some T lymphocytes destroy infected cells that have become infected or cancerous. Others indirectly attack foreign invaders by producing cytokines, signaling chemicals that the immune system needs to launch a larger response, overwhelming the pathogen. Both T and B lymphocytes can form memory cells, allowing faster and more efficient immune responses to familiar pathogens during future  infections. 

Best known for killing virally infected cells, NK cells are integral to the body’s natural defense against cancer. NK cells can kill cancer cells without priming or activation, making them a faster defense mechanism than T cells. NK cells naturally patrol the tissue and bloodstream looking for non-self targets. For example, NK cells recognize receptors on cancerous cells and flip them “on,” activating the lysis of the cancer cell.

How to Isolate Leukocytes From a Leukopak

 A leukopak is an enriched apheresis product collected via leukapheresis—a protocol designed to extract leukocytes (white blood cells)—and return the remaining cells and plasma to the donor. The product of this procedure is a highly concentrated solution of white blood cells. Leukocytes can be isolated from leukopaks via various blood separation techniques and more specific cell separation techniques. Once the cell isolation is complete, leukocytes can be used in various ways;  drug development, cell therapy research, immunotherapy, vaccine development, cell-therapy process development, and clinical trials.

Leukopaks contain up to 20 times as many monocytes as the same volume of whole blood, making them an ideal starting material for researchers looking to study monocytes and other agranulocytes. Many blood cell subsets can be isolated from a leukopak. For instance, it is not uncommon to remove granulocytes via granulocyte isolation for downstream use in assays. Granulocytes could also be removed to create a sample with a high concentration of PBMCs.

Similar to granulocytes, several other important blood cells can be isolated from leukopaks—such as B cells and T cells—that are necessary to explore human memory cells and the adaptive immune response. In addition to granulocytes and monocytes, basophil isolation can provide insight into the signaling chemicals responsible for rapid leukocyte transportation.

Akadeum Leukopak Processing Products for Leukocytes Applications

Regardless of the desired cell type to be isolated, Akadeum Life Sciences has a separation kit that will provide quick and gentle blood cell isolation. Our microbubble technology maintains the quality and integrity of the isolated cell solution or leukopak.

Additionally, our microbubbles can process an entire leukopak for cell separation in only 60 minutes. Cell separation is a fragile process where cells can become damaged during centrifugation, buffy coat formation, magnetization, and other steps. Fragility presents additional risk to a lengthy and imperative first step in cell and immunotherapy research. Akadeum’s technology revolutionizes cell separation techniques by simplifying an otherwise difficult procedure. 

Explore the applications of our Human T Cell Isolation Kit to see how accurate our microbubbles can make the cell separation process.

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