BIO1022 Chapter Notes - Chapter Prescribed: Antigen, Histocompatibility, Mutation Rate
30 May 2018
School
Department
Course
Professor
BIO1022 – Readings – Week 10
concepts 43.1 - 43.2 - the host’s immune system response to pathogens
concept 43.1
- in innate immunity, recognition and response rely on traits common to groups
of pathogens
- innate immunity is found in all animals and plants
- vertebrates - innate immuntity serves as both an immediate defences against
infection and as the foundation for adaptive immune defences
- innate immunity of invertebrates
• insects in terrestrial and freshwater habitats - rely on their exoskeleton as
the first line of defence against infection
•
o composed largely of the polysaccharide chitin, the exoskeleton
provides an effective barrier defence against most pathogens
o chitin also lines the insect intestine where it blocks infection by
many pathogens ingested with food
o lysozyme - an enzyme that breaks down bacterial cell walls further
protects the insect digestive system
• any pathogen that breaches an insect’s barrier defences encounters a
number of internal immune defences
•
o immune cells called haemocytes travel throughout the body in the
haemolymph - the insect circulatory fluid
o
▪ some haemoytes - ingest and break down bacteria and
other foreign substances - a process known as
phagocytosis
▪ other haemoctyes release chemicals that kill pathogens and
help entrap large parasites
▪ encounters with pathogens in the haemolyphm cause
haemocytes and certain other cells to secrete antimicrobial
peptides - which are short chains of amino acids
▪
▪ these peptides circulate throughout the body of the
insect and inactivate or kill fungi and bacteria by
disrupting their plasma membranes
- innate immunity of vertebrates
• among jawed vertebrates, innate immune defences coexist with the more
recently evolved system of adaptive immunity
• barrier defences
•
o in mammals - barrier defences block the entry of many pathogens
o these defences include the skin and the mucous membranes lining
the digestive, respiratory, urinary and reproductive tracts
o the mucous membranes produce mucous - a viscous fluid that
traps pathogens and other particles
find more resources at oneclass.com
find more resources at oneclass.com
o saliva, tears and mucous secretions that bathe various exposed
epithelia provide a washing action that also inhibits colonisation
by fungi and bacteria
o body sections inhibit microbial entry
o body secretions also create an environment that is hostile to many
pathogens
o lysozyme in tears, saliva and mucous secretions destroys the cell
wall of susceptible bacteria as they enter the openings around the
eyes or the upper respiratory tract
• cellular innate defences
•
o many pathogens that defeat the barrier defences of mammals are
engulfed by phagocytic cells that use several types of receptors to
detect viral, fungal or bacterial components
o mammalian toll-like receptors - TLR - bind to fragments of
molecules normally absent from the vertebrate body but
characteristics of a set of pathogens - each receptor recognised a
molecular pattern characteristic of a group of pathogens
o detection of invading pathogens in mammals triggers phagocytosis
and destruction
o the two main types of phagocytic cells in the mammalian body are
neutrophils and macrophages
o
▪ neutrophils
▪
▪ circulate in the blood
▪ are attracted by signals from infected tissues and
then engulf and destroy the infecting pathogens
▪ macrophages
▪
▪ larger phagocytic cells
▪ some migrate throughout the body
▪ whereas other reside permanently in organs and
tissues where they are likely to encounter
pathogens
o two other type of phagocytic cells
o
▪ dendritic cells
▪
▪ mainly populate tissues, such as skin, that contact
the environment
▪ stimulate adaptive immunity against pathogens they
encounter and engulf
▪ eosinophils
▪
▪ often found beneath mucosal surfaces
▪ important in defending against multicellular
invaders, such as parasitic worms
find more resources at oneclass.com
find more resources at oneclass.com
▪ upon encountering such parasites, eosinophils
discharge destructive enzymes
o natural killer cells
o
▪ these cells circulate through the body and detect the
abnormal array of surface proteins characteristic of some
virus-infected and cancerous cells
▪ do not engulf stricken cells - instead they release chemicals
that lead to cell death - inhibiting further spread of the virus
or cancer
o many cellular innate defences in vertebrates involve the lymphatic
system - a network that distributes the fluid called lymph
throughout the body
o
▪ some macrophages reside in lymph nodes p where they
engulf pathogens that have entered the lymph from the
interstitial fluid
▪ dendritic cells reside outside the lymphatic system but
migrate to the lymph nodes after interacting with
pathogens
▪
▪ interact with other immune cells, stimulating
adaptive immunity
o antimicrobial peptides and proteins
o
▪ in mammals - pathogen recognition triggers the production
and release of a variety of peptides and proteins that attack
pathogens or impede their reproduction
▪ some of these defence molecules function like the
antimicrobial peptides of insects, damaging broad groups of
pathogens by disrupting membrane integrity
▪ others including the interferons and complex proteins are
unique to vertebrate immune systems
▪ interferons
▪
▪ are proteins that provide innate defence by
interfering with viral infections
▪ virus infected body cells secrete interferons - which
induce nearby uninfected cells to produce
substances that inhibit viral replication
▪ interferons limit the cell to cell spread of viruses in
the body - helping control viral infections such as
colds and influenza
▪ complement system
▪
▪ infection fighting
▪ consists of roughly 30 proteins in blood plasma
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Bio1022 readings week 10 concepts 43. 1 - 43. 2 - the host"s immune system response to pathogens concept 43. 1. In innate immunity, recognition and response rely on traits common to groups of pathogens. Innate immunity is found in all animals and plants. Vertebrates - innate immuntity serves as both an immediate defences against infection and as the foundation for adaptive immune defences. In adaptive immunity, receptors provide pathogen-specific recognition. Vertebrates are unique in having both adaptive and innate immunity. Adaptive immunity defends against infection of body fluids and body cells. Humoral immune response - occurs in the blood and lymph - which were once called body humours - fluid: antibodies help neutralise or eliminate toxins and pathogens in the blood and lymph. Cell mediated immune response specialised t cells destroy infected host cells. Both responses can include both a primary immune response and a secondary immune response with memory cells enabling the secondary response.
