![]() ![]() Local inflammatory cells, such as macrophages and mast cells, detect pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) and release cytokines as a signal for leukocytes to migrate out of circulation. Leukocyte migration to sites of injury or infection is mediated by pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) present on microbes and damaged tissue respectfully. The major groups are B lymphocytes and T lymphocytes.Īll white blood cells or leukocytes are involved in immune system function however, the specific roles and functions vary for each blood cell type.ĭiapedesis (also called Extravasation, or Leukocyte Adhesion Cascade) Lymphocytes subdivide into several groups using the cluster of differentiation (CD) markers. Larger lymphocytes, such as activated lymphocytes, have indented nuclei and are 9 to 18 µm in diameter with more cytoplasm containing azurophilic granules. The small lymphocytes are similar in size to red blood cells, have spherical heterochromatic nuclei, and scant cytoplasm. Lymphocytes constitute approximately 25% white blood cells, are of varying sizes, and have spherical nuclei. There is abundant cytoplasm, and the lysosomal granules at the resolution of the light microscope give the cytoplasm bluish-gray color. These cells constitute 4 to 8% of white blood cells, are 12 to 15 µm in diameter, have large nuclei that are indented or C- shaped, which can be eccentric. Monocytes are precursor cells for the mononuclear phagocytic system, which include cells such as macrophages, osteoclasts, microglial cells in connective tissue and organs. These cells have similar functions as mast cells.Īgranulocytes consist of lymphocytes and monocytes, and while they lack specific granules, they do contain azurophilic granules. The basophilia of the granules is due to the presence of heparin and sulfated glycosaminoglycans. These cells have life spans of a few days, and when activated in connective tissue, undergo apoptosis and are then removed by macrophages.Įosinophils have a bi-lobed nucleus with large cytoplasmic specific granules that are eosinophilic, staining red to pink.īasophils are 12 to15 µm in diameter, have bi-lobed or S-shaped nuclei, and contain cytoplasmic specific granules (0.5 µm) in diameter that stain blue to purple. ![]() Neutrophils, when activated, migrate into the tissues via diapedesis. Neutrophils contain specific granules in the cytoplasm that cannot be resolved by light microscopy and therefore give the cytoplasm a pale pink color. Thus, they are also called polymorphonuclear neutrophils. Neutrophils are 12 to 15 µm in diameter, have multi-lobed nuclei typically consisting of 3 to 5 segments joined by thin strands, or isthmuses. Histologically, granulocytes can be distinguished from one another by the morphology of their nucleus, their size, and how their granules stain. These cells also all have azurophilic granules (lysosomes) and specific granules that contain substances unique to each cell's function. Neutrophils, basophils, and eosinophils are all granulocytes. Leukocytes can be classified as granulocytes and agranulocytes based on the presence and absence of microscopic granules in their cytoplasm when stained with Giemsa or Leishman stains. ![]()
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