Cells of the Immune System Flashcards
What are the types of Lymphocyte
B cells, T cells, and NK cells
What are the types of granulocytes
Neutrophils, Eosinophils, Basophils, mast cells, monocytes (macrophages and dendritic cells)
True or false: NK and T cells kill infected Ella by apoptosis
True
How do NK and T cells induce apoptosis
T cell recognised infected cell and NK cell releases lytic granules that kill the virus infected cells
What is the activated function of a macrophage
Yeah phagocytosis and Activation of bactericidal mechanisms
What is the activated function of a dendritic cell
Antigen uptake I’m peripheral sites and antigen presentation
What is the activated function of a neutrophil
Phagocytosis and activation of bactericidal mechanisms
What is the activated function of an eosinophil
Killing off antibody Coated parasites
Stages of phagocytosis
Adherence
Ingestion (phagosome)
Digestion (phagolysosome)
Excretion (exocytosis)
Characteristics of Neutrophils (Granulocytes)
Primary and secondary granules
First cells to arrive at site of infection
FXN: phagocytosis, neutrophil extracellular traps
Describe the difference between primary and secondary neutrophils
Primary: larger molecules, peroxidase, lysozyme
Secondary: collagenases, lactoferrin, lysozyme
Describe characteristic of monocytes
Circulate in blood for ~8 hours after leaving the bone marrow.
Migration into the tissues and differentiation into macrophages and dendritic cells
Characteristics of macrophages
Differentiate tissues from monocytes
- increased cell size 5-10x
- more intracellular organelles, proteolytic enzymes, secretion of soluble factors
What are the types of macrophage
Resident macrophages: diff functions for diff tissues
Wandering macrophages: antigen presenting cells that travel within and between tissues to phagocytose
Characteristics of Dendritic cells
Express MHC 1, MHC 2, CD4 and CD8 molecules
FXN: phagocytes, antigen presenting cells (APC)
- Phagocytosis of pathogen/antigen —> maturation —> transport to lymph node
- antigen presentation to T cells
Characteristics of eosinophils
Phagocytic granulocytes
Mostly in connective tissue under epithelium
Cell surface receptors for cytokines, complement, Fc receptor for IgE (—> andtiboy dependant cell cytotoxicity - ADCC)
Explain the effector funstion of eosinophils
Upon activation they release free radicals and toxin proteins from granules that kill microorganisms and parasites but can also induce allergic reactions.
They also release prostaglandins, leukotrienes and cytokines that amplify the inflammatory response which activated epithelial cells to recruit leukocytes
Characteristics of Basophils
Non-phagocytic granulocytes
Recruited from blood into tissues
Cell surface receptors for cytokines and Fc fragment of IgE —> ADCC
Explain the effector function of basophils
Release histamine —> increase in vascular permeability
Defence against parasites with eosinophils
Can induce allergic reactions
Characteristics of Mast cells
Differentiate only upon entering tissues In connective tissue, around blood and lymph vessels and nerves Granules with histamine Secrete cytokines Receptors for Fc of IgE —> ADCC
Describe effector function of Mast cells
Can induce allergic reactions (histamine)
Role in inflammation
Characteristics of NK cells
Kill only infected or cancerous host cells by detecting the “missing self”
Cytotoxic granules containing perforin and enzymes
Express receptors on cell surface
Describe the receptors on the cell surface of NK cells
Activating receptors: detection markers of stress on infected or cancerous cells, trigger killing of target cells
Inhibiting receptors: prevent NK cells from killing normal cells by detecting Normal levels of MHC 1 molecule
Explain the activation of NK cells
Apoptosis indies by: - fas-dependant mechanism - fas-independant mechanism - antibodies: ADCC MHC 1 alone will not activate but will in conjunction with activating Ligands Activating ligands alone can activate
What is MHC
Major Histocompatibility complex, a cluster of over 200 genes on chromosome 6
They present antigens on the cell surface
Membrane bound glycoproteins
Describe MHC 1 glycoproteins
Expressed on surface of every uncleared host cell
Spit the signal pathogenic cells to T cells
Present only endogenous (intracellular) antigens
Describe MHC II glycoproteins
Express only on surface of professional APC (dendritic cells, B cells, Macrophages)
Present only on EXOGENOUS (extracellular) bacteria, viruses, parasitic worms, pollen, dust, toxins
What is a receptor
A protein that binds to substrates to pick up a change, send that signal to a cell and to initiate a signalling cascade stimulating or inhibiting a response
What are the types of receptor
Intracellular
- cytoplasmic: in cytosine, swim around to pick up pathogenic structures and relay to nucleus
- nuclear: sit in nucleus and gives instructions/signals to genetic material
Extracellular
What are the functions of receptors
Specific binding to molecules: peptide, antigens, neurotransmitters, hormones, drugs, toxins etc.
Conformational changes to receptor lead to downstream effects
- Activation of signalling
Change of membrane potential
Describe cytokines
- Low Mr proteins secreted by cells of immune and other systems
- Bond to specific cell-surface receptors and induce profound changes in target cells
- can act in an autocrine, paracrine or endocrine fashion
Function of receptors, cytokines and chemokines
Activation e.g. Th1 lymphocytes activate macrophages through IFN-gamma Proliferation Differentiation Chemotaxis (chemokines) Cell death and survival Etc.
Examples of cytokines families
- Haematopoietin family: e.g. Interleukin: produced by leukocytes and target other leukocytes
- interferon family (mainly anti-viral function)
- chemokine (adhesion, chemotaxis and activation of leukocytes)
- TNF family (inflammation)
