Introduction Flashcards
What are the three layers of defence?
Physical barriers, innate IS and adaptive IS
How does the skin act as a protective barrier?
The tough protein keratin found in the skin renders it impermeable to most infectious agents when intact. Damage to skin increases infection risk.
What acids are secreted by the skin to limit bacterial growth?
Lactic acid and fatty acids. Low pH also limits bacterial growth
Name the bactericidal components of secreted body fluids
hydrochloric acid in gastric juice. spermine and zinc in semen, lactoperoxidase in milk, alpha lysozyme in tears, nasal secretions and saliva.
How does mucous limit bacterial growth?
Mucous is secreted by epithelial membranes, acts as a protective barrier by preventing the adhesion of bacteria to epithelial cell, preventing colonisation. Microbial and other foreign particles are trapped in the mucous membrane and transported out of the body through ciliary beating (mucosal-ciliary escalator in lungs), coughing and sneezing.
Where do the vast majority of infections originate?
Mucosal surfaces
What is microbial antagonism
This occurs due to normal bacterial flora (commensials) suppressing the growth of potentially pathogenic bacteria and fungi through competition for essential nutrients. Commensials can also produce microbicidal substances which are aimed to kill and limit the growth of pathogenic bacteria. When protective commensals are disturbed by antibiotics, susceptibility to opportunistic infections increase; Candidia albicans and Clostridium difficile.
How is microorganism recognition mediated?
Through antigens, which are glycoprotein/ proteinaceous structures on the surface of cells.
What are the two types of immune responses?
innate and adaptive
What are the characteristics of the innate response?
Broadly specific, does show increased pathogen clearance following subsequent infections by the same pathogen, i.e. no immunological memory.
What are the cells of the innate response?
Monocytes/Macrophages, dendritic cells, neutrophils, eosinophils, basophils, mast cells, natural killer cells.
True or false, Mast cells are located in the blood?
False, they are located in tissues, basophils (although independently derived but similar) are located in the blood.
Mononuclear phagocytes structure:
In blood, they are monocytes in tissues they develop into macrophages. They have a large nucleus, little cytoplasm, indentation of the nucleus.
Neutrophil structure
Most numerous leukocyte, also known as polymorphonuclear phagocyte as they have a multilobed nucleus. They have a relatively large, granulated cytoplasm.
Eosinophils
Have a granulated cytoplasm and are also polymorphonuclear phagocytes; multilobed. Eosin stain stains these cells red. Act against large parasites. Not efficient at phagocytosis however their mechanism of killing is by releasing granule contents, i.e. extracellular killing
