Peripheral Blood Mononuclear Cells (PBMCs) are a diverse group of white blood cells circulating in the blood that play a central role in the body’s immune system. The term “peripheral” means these cells are found in circulating blood, not in blood-forming organs like bone marrow. As “mononuclear cells,” they have a single, round nucleus, distinguishing them from other white blood cells with multi-lobed nuclei. PBMCs are crucial for defending the body against infections, cancer, and other foreign substances, making them a significant area of study in medical research.
Cellular Components
Peripheral Blood Mononuclear Cells represent a heterogeneous population primarily composed of lymphocytes and monocytes, along with a small percentage of dendritic cells. Lymphocytes, which include T cells, B cells, and natural killer (NK) cells, typically constitute 70% to 90% of PBMCs. T cells are the most abundant lymphocyte subset, making up about 45-70% of PBMCs, followed by B cells (5-15%) and NK cells (5-10%).
Monocytes account for 10% to 30% of PBMCs. These are the largest white blood cells in peripheral tissue and can differentiate into macrophages and dendritic cells upon migrating into tissues. Dendritic cells are rare within PBMCs, typically making up only 1% to 2%.
Key Functions
PBMCs orchestrate immune responses, defending against pathogens and abnormal cells. Lymphocytes are central to both adaptive and innate immunity.
T cells are involved in cell-mediated immunity, directly attacking infected or cancerous cells. Helper T cells also coordinate immune responses by signaling to other immune cells. B cells contribute to humoral immunity by producing antibodies that target and neutralize foreign invaders. Natural killer (NK) cells, part of the innate immune system, provide rapid defense by directly killing virus-infected or tumor cells.
Monocytes play a role in innate immunity by engulfing harmful microorganisms through phagocytosis. They also act as antigen-presenting cells, processing foreign particles and presenting them to T cells, bridging innate and adaptive immune responses.
Significance in Health and Research
PBMCs are instrumental in health and scientific investigation due to their accessibility and reflection of systemic immune status. They serve as a source of biomarkers for diagnosing and monitoring diseases, including metabolic disorders, arthritis, and neurodegenerative diseases. Changes in the gene expression or protein profiles within PBMCs can indicate disease progression or response to treatment.
In drug discovery and development, PBMCs are used for toxicity screening and assessing immune responses to new therapeutic agents. This allows researchers to predict potential side effects and evaluate drug efficacy before clinical trials. PBMCs are also used in vaccine development, enabling scientists to study immune system reactions to vaccine candidates and identify optimal protection strategies.
PBMCs hold promise in advanced cell-based therapies, notably cancer immunotherapy. They are the source for generating Chimeric Antigen Receptor (CAR) T-cells, where a patient’s T cells are genetically modified to recognize and destroy cancer cells. This non-invasive source of immune cells provides a platform for understanding immune mechanisms and designing targeted interventions against infectious diseases, autoimmune disorders, and cancers.