BMS2045 1b Cells of the immune system 2024 PDF

Theme 1 Cells of the immune system Aims To provide a familiarity with the different cells involved in immune responses Learning outcomes List, recognise and describe all the different types of cells involved in immunity Identify the different cells’ key characteristics and functions and explain how...

Theme 1 Cells of the immune system Aims To provide a familiarity with the different cells involved in immune responses Learning outcomes List, recognise and describe all the different types of cells involved in immunity Identify the different cells’ key characteristics and functions and explain how you can distinguish between them Cells involved in immunity Includes all white blood cells (leukocytes) and some others (endothelial cells, adipocytes and epithelial cells) Derived from self-renewing stem cells in bone marrow which differentiate under the influence of growth factors into pluripotent stem cells and then progenitor cells Progenitor cells and ‘lineages’ for leukocytes include myeloid & lymphoid with others suspected All contribute in a variety of ways to the innate and/or adaptive immune responses Immune cells from 2 main lineages: NKT cell Dendritic cells Granulocytes/ polymorphonuclear cells Macrophages White blood cells (leukocytes) move from bone marrow out into the blood and/or tissues where they can differentiate further and perform a wide variety of functions… Identifying cells Can use cell size and how granular the cytoplasms is… Cells have been identified by researchers by specific molecules they express (usually on the surface but sometimes internally) In 1982, amid growing confusion of alternative names being used, a group of scientists met in Paris to decide on a strict nomenclature The ‘CD’ system (Cluster of Differentiation) was established and is used today (371 in humans as of 2014 meeting in Australia) T cell CD3 no CD19, CD21 or CD14 B cell Monocyte CD19 & CD21 no CD3 or CD14 CD14 no CD3, CD19 or CD21 The myeloid lineage Innate Lymphoid Cells NKT cell Mast cell Dendritic cells Granulocytes/ polymorphonuclear cells Macrophages Myeloid progenitor cell Gives rise to polymorphonuclear cells (polymorphs or PMNs), monocytes, megakaryocytes, mast cells & erythrocytes Polymorphs include neutrophils, eosinophils and basophils also called granulocytes (60-70% white blood cells) Monocytes are blood borne; in tissues they become macrophages (MF) Bone marrow development Development from progenitor cells into specific cell types relies on the secretion of various hormones & growth factors such as: Cytokines or Inter-Leukins, (IL) Colony Stimulating Factors (CSF) within the bone marrow and later in the tissues Granulocytes ‘Polymorphonuclear’ cells (Morgan and Yang, Blood, 2013) Neutrophils Large cells (10-20 microns in diameter), only live about 2-3 days 90% of granulocytes are neutrophils Neutral staining cytoplasmic granules containing enzymes e.g. lysozyme Highly phagocytic, kill bacteria by microbicidal mechanisms Secrete NETs (neutrophil extracellular traps) Most important cell in non-viral infections Have receptors for antibody Eosinophils Contain prominent granules, which stain red with eosin & composed of a crystalline core cytotoxic for parasites; EOSINOPHIL BASIC PROTEIN Important in immunity to helminth (worm) infections When stimulated, release mediators that promote inflammation Phagocytic, though this is not a major function Have receptors for IgE (antibody) Basophils