> See also: > - [[Blood Cells]] > - [[Cell Exhaustion]] ![[Cells of the Immune System.png|500]] # Cells of the Immune System There are a wide variety of different [[Blood Cells]] that play a role in the immune system's defense. It can be useful to classify the different types of immune system cells based on their location within the body. Most cells within the [[Innate Immunity|innate immune response]] are found within the tissue and blood stream White blood cells ([[Blood Cells|leukocytes]]) are the primary cells involved with the immune system. Cells of the immune system can often interact with other cells through chemical signaling. The most abundant leukocytes are the **neutrophils** - Eosinophils - Basophils: release vasoactive substances, promoting [[Inflammation & Fevers|inflammation]] - Mast Cells - Neutrophils - [[Macrophages]] - Monocytes - Dendritic Cells - --- The erythroid progenitor gives rise to erythroid lineages of blood cells—erythrocytes and megakaryocytes. Platelets are derived from megakaryocytes by fragmentation and are non-nucleated cell fragments. The main function of erythrocytes or RBCs is to carry oxygen throughout the body. Granulocytes such as eosinophil defend against helminth worms and other intestinal parasites, whereas highly phagocytic neutrophils capture, engulf, and kill bacteria by phagocytosis. Dendritic cells are key cells in initiating adaptive immune response since they capture pathogens in infected tissues and carry them to secondary lymphoid organs where adaptive immune responses are initiated. 1. **[[The Lymphatic System|Lymphoid Cells]]** - Composed of *lymphoid tissue* - 20-50% of white - T cells, B cells, and NK cells 2. **Mononuclear Phagocytes** - Monocytes that circulate in the blood - Macrophages found in tissues (sentinels) 3. --- ![[Myeloid Cells of the Immune System.png]]