monocits

Monocits, commonly known as monocytes, are a type of white blood cell belonging to the innate immune system. They arise from the myeloid lineage in the bone marrow and circulate in the bloodstream before migrating into tissues, where they differentiate into macrophages or dendritic cells that help coordinate immune responses and remove debris.

In humans, monocytes are classified into subtypes based on surface markers: classical (CD14++ CD16-), intermediate (CD14++ CD16+), and non-classical (CD14+ CD16++). Functionally, classical monocytes respond quickly to inflammation and are highly phagocytic, while non-classical monocytes patrol the endothelium. In mice, analogous populations are described using different markers such as Ly6C. Monocytes in tissues contribute to various roles depending on the local environment, including host defense, tissue repair, and regulation of other immune cells.

Primary functions of monocytes include phagocytosis of pathogens and dead cells, antigen presentation to T cells, and secretion of cytokines such as IL-1β, TNF-α, and IL-6. They also participate in wound healing and tissue remodeling. Through differentiation into macrophages or dendritic cells, monocytes bridge innate and adaptive immunity.

Clinical relevance: elevated monocyte counts (monocytosis) can occur with chronic infections, autoimmune or inflammatory diseases, and recovery from acute infections. Monocytopenia is less common. Monocytes contribute to atherosclerotic plaque macrophage populations and can participate in various organ macrophage and dendritic cell pools.

Detection: monocytes are measured in a complete blood count with differential. Normal absolute counts are roughly 200–800 cells per microliter (about 0.2–0.8 x 10^9/L), representing about 2–8% of leukocytes; values vary by laboratory.

---