Flashcards in Immunology Deck (207)
What are the four types of innate immunity?
Anatomical barriers, physiological barriers, phagocytic barriers and inflammatory barriers
What are examples of anatomical barriers?
Skin and mucous membranes
What are examples of physiological barriers?
Temperature, acidity, soluble factors
What are examples of phagocytic barriers?
What are the characteristics of the epidermis?
Dead outer, impermeable, nutrition by diffusion, sheds every 10-15 days, made up of keratinocytes
What are the characteristics of the dermis?
Vascularised, connective tissue, glands, sebum secretion
What is the most common entry point for pathogens?
What composes the mucous membranes?
Outer epithelial and connective tissue layers
What makes up mucus?
Mucin (glycoproteins), anti-microbial, proteins, inorganic salts
How does the influenza virus evade the mucous membrane defence?
It has specialised adhesion molecules
How does gastric acidity destroy most ingested pathogens?
Low pH denatures enzymes, affects transport mechanisms and metabolic activity
What are the soluble factors and how to they defend the body?
Lysozyme (cleaves peptidoglycans, weakens cell wall, osmotic lysis), interferon (anti-viral activity, prevents viral replication), opsonins (ficolin, surfactant proteins, mannose binding protein, promotes phagocytosis), complement (lyse target cells, enhance phagocytosis and chemotaxis)
What are cells of the myeloid lineage of the innate immune system?
Neutrophils, monocyte/macrophage, eosinophils, basophils, mast cells
What are cells of the lymphoid lineage of the innate immune system?
Natural killer cells
What is the difference between endocytosis and phagocytosis?
Endocytosis is the ingestion of macromolecules, phagocytosis is the ingestion of particles. All cells are endocytic but only certain cells can phagocytose.
What are the two major mechanisms of endocytosis?
Pinocytosis (nonspecific) and receptor-mediated endocytosis (specific)
What is the mechanism of phagocytosis?
Plasma membrane expands to form pseudopods. Pseudopod retracts and seals intelf into a phagosome. Phagosome fuses with lysosomes. Processing then similar to endocytosis.
What is the function of opsonins?
Tagging microbes to make it more palatable for phagocytes
What are the two functions of complement?
Generate reaction products to clear antigens and generate an inflammatory response
How is complement activated in adaptive immunity?
Classical pathway - C1 recognises immune complexes formed by the binding of antibodies to antigen
How is complement activated in innate immunity?
Alternative pathway - non-specific activation by bacteria, fungi, parasites and viruses, C3b deposits on surfaces of microbes. Lectin pathway - mannose binding lectin attaches to mannose sugar residues on bacteria surface
What is the first important mechanism which occurs following complement activation?
Opsonisation - coats surface with C3b proteins to promote phagocytosis
What is the second important mechanism which occurs following complement activation?
Initiates an inflammatory response - release anaphylatoxins C3a, C4a and C5a, which bind to immune cells to trigger the inflammatory response. Anaphylatoxins are also chemoattractants to phagocytes
What is the third important mechanism which occurs following complement activation?
Punches holes in cell membranes - formation of the membrane attack complex on surface of cells, bacteria and evneloped viruses
Define the inflammatory response
A complex sequence of events that occur following tissue damage caused by invasion or wounding
How are leukocytes transported?
In the circulatory system
What is the function of precapillary sphincters?
Prevent the backflow of blood
What are the three types of capillary?
Continuous, fenestrated, sinusoidal
What are the features of continuous capilaries?
Least permeable, most common (skin, muscle), don't let cells pass through in normal homeostatic conditions