Innate Immunity Flashcards
what are routes of entry for pathogens through mucosal surfaces?
- airway
- GI
tract - GU
what are routes of entry for pathogens through external epithelia?
- external surface (skin)
- wounds and abrasions
- insect bites
what pathogen causes meningococcal meningitis?
neisseria meningiditis
what pathogen causes syphilis?
treponoma pallidum
what pathogen causes athlete’s foot?
tinea pedis
what are the phases of innate immunity?
- infection
- recognition by preformed nonspecific effectors
- removal of infectious agent
- 0-4 hours
what are the phases of early induced response?
- infection
- recruitment of effector cells
- recognition and activation
- removal of infectious agent
- 4-96 hours
what are the phases of adaptive immune response?
- infection
- transport of antigen to lymphoid organs
- recognition by naive B and T cells
- clonal expansion of effector cells
- removal of infectious agents
- > 96 hours
what are some mechanical barriers to infection?
- tight junctions between cells
- air and fluid flow across epithelium
- movement of mucus by cilia
what are some chemical barriers to infection?
- fatty acids on skin
- enzymes: lysozyme in saliva, swear and tears
- low pH in stomach
- antibacterial peptides: defensins (skin and gut), cryptidins (gut)
what are some microbiological barriers to infection?
normal flora compete for nutrients and attachment (biofilms), and also produce antibacterial substances (colicins)
what are monocytes?
- 1 of 3 types of phagocytic cell of immune system
- circulate in bloodstream
- differentiate into macrophages in tissue
what is the role of a macrophage?
- phagocytosis and killing of microorganisms
- activation of T cells and initiation of immune response
what are examples of granulocytes?
- neutrophils
- eosinophils
- basophils
what is an alternate name for granulocytes?
polymorphonuclear (PMN) leucocytes - due to shape of nuclei
what is the role of a neutrophil?
- phagocytosis and killing of microorganisms
- most numerous and important cell of innate immunity
what does a deficiency of neutrophils lead to?
overwhelming bacterial infections
what is the role of an eosinophil?
- killing of antibody-coated parasites through release of granule contents
- important in parasite defence
what is the function of a mast cell?
- expulsion of parasites from body through release of granules containing histamine and other active agents
- well known due to IgE mediated triggering in allergies
- effect vascular systems
what is the role of a basophil?
function similar and complementary to eosinophils and mast cells
what are lymphocytes?
- B or T cells
- B cells produce antibody
- T cells becoming cytotoxic cells (CD8) or helper cells (CD4)
what are natural killer (NK) cells?
- large granular lymphocytes
- can recognise virally infected cells non-specifically
what are dendritic cells?
- potentially the most important immune cell
- bridges innate and adaptive immune responses
- specialised in antigen uptake and antigen presentation
what is the difference between NK cells and T cells?
- NK cells are not antigen specific
- don’t undergo length clonal expansion of T cells in lymph nodes when virus detected
what is the role of the complement cascade?
- part of immune system that enhances (complements) ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism
- promotes inflammation (heat labile component of plasma)
- attacks the pathogen’s plasma membrane
what are the 3 activation pathways that trigger the complement cascade?
- classical
- lectin
- alternative
what is the first phase of the classical pathway of the complement cascade?
antibody binds to specific antigen on pathogen surface
what is the first phase of the lectin pathway of the complement cascade?
mannose-binding protein binds to pathogen surface
what is the first phase of the alternate pathway of the complement cascade?
pathogen surface creates local environment conducive to complement activation
what are the results of complement activation?
- recruitment of inflammatory cells
- opsonisation of pathogens, facilitating uptake and killing by phagocytic cells
- lysis and death of pathogens
what is the classical pathway initiated by?
activation of C1 complex
what is the lectin pathway activated by?
- MBL
- MASP-1 and 2
what is the alternative pathway activated by?
spontaneous hydrolysis of serum C3
