White Cells - Leukocytes Flashcards
White cells are comprised of which 3 parts?
Granulocytes, monocytes and lymphocytes
What are granulocytes and their function?
Consists of neutrophils, basophils and eosinophils, all have granules present in the cytoplasm containing agents to breakdown phagocytosed micro-organisms
What are monocytes?
Precursors (substance from which another is formed) of macrophages, mature in tissues to macrophages
Where are granulocytes, monocytes and lymphocytes derived from?
HSCs give rise to myeloid and lymphoid stem cells -
Myeloid stem cells: Granulocytes and monocytes
Lymphoid stem cells: Lymphocytes
Which growth factors control the synthesis of granulocytes and macrophages?
Granulocyte-colony stimulating factor (G-CSF), Macrophage colony stimulating factor (M-CSF) and Granulocyte-macrophage colony-stimulating factor (GM-CSF)
Functions of Neutrophil granulocytes?
Chemotaxis, phagocytosis, killing of phagocytosed bacteria
Functions of monocytes and macrophages?
Chemotaxis, phagocytosis, killing of some micro-organisms, antigen presentation
Functions of eosinophil granulocytes?
Neutrophil functions, main defence against parasitic infections, regulating some immediate-type hypersensitivity reactions
Functions of basophil granulocytes
Neutrophil functions, mediation of immediate-type hypersensitivity reactions, modulation of inflammatory responses by releasing heparin (anti-coagulant) and proteases
Lymphocytes give what type of immunity?
Humoral and cellular immunity
What is the maturation of a granulocyte called, and what is the process?
Granulopoiesis - myoblast, promyelocyte, myelocyte, band forms, neutrophil
Cell division stops at band forms
Maturation of granulocytes is characterised by a reduction in cell size together with the development of granules that contain agents essential for cell function
Features of the neutrophil and how they function?
Segmented nucleus
Full of cytoplasmic granules
Spend 7 - 10 hours in circulation, then migrates towards tissues via chemotaxis (cytokines released from the tissue attracts neutrophils)
Adheres to vessels in infected area (margination) and migrates to tissue
Engulf, kill and digest microorganisms (phagocytosis)
Release inflammatory mediators
How do neutrophils phagocytise micro-organisms?
Release their (the neutrophil’s) toxic intracellular contents via 2 methods
What are the 2 methods for the neutrophil to release toxic contents?
- Superoxide dependent - ‘respiratory burst’ where the neutrophil releases a reactive oxygen species, which is a substrate for myeloperoxidase (MPO) leading to toxic substance production
- Oxygen dependent - antimicrobial agents are released e.g. defensins, gelatinases
Features of the eosinophil and how they function?
Spend less time in circulation
Defends against parasitic infections
Features of the basophil and how they function?
Granules contain stores of histamine (vasodilator - promotes blood flow) and heparin (prevents blood from clotting too quickly), as well as proteolytic enzymes
Appears in inflammatory responses