Week 3 - Infection and Immunity Flashcards
3 things our immune system is designed to do
- prevent entry
- prevent spread/growth
- remove threat
What are the main components of the immune system?
- organs and tissues
- cells
- molecules/chemical mediators
What is a pathogen
a microorganism that can cause disease
What is pathogenicity
the capability of a microorganism to cause disease
What is an infection?
a pathogen has reproduced in the host’s body
How are infectious diseases caused?
caused by pathogens (microorganisms that invaded; multiply; cause damage)
Bacteria
- prokaryotic, single cell organisms, rigid cell wall
- contain DNA, RNA, and ribosomes (in cytoplasm)
- Can survive and divide outside a living host
- Named based on shape and characterisitics
Viruses
- small intracellular parasite
- requires a living host to replicate
- a protein coat with a core that contains RNA or DNA
- called virion when it is outside of a host
Fungi
- found everywhere in the environment
- eukaryotic single cells (yeast) or chains of cells (molds)
- can produce spores that become airborne (inhalation can trigger allergic reaction)
- only certain fungi are pathogenic (worse for people who are immunocompromised)
Protozoa
- parasites (pathogenic protozoa)
- complex eukaryotic organisms (unicellular, motile)
Prions
- don’t contain genetic material
- infection is transmitted by protein particles (prions) that are able to self-propagate (induces proteins in the brain to misfold -> nonfunctional -> neurodegeneration)
- systems are neuro-degenerative
Infection - modes of transmission
- direct contact
- indirect contact
- droplets
- aerosol
- vector-borne
Infection reservoir
the source carrying the infection
Innate immune response: defense mechanism
physical and chemical barriers, inflammatory response
Adaptive immune response: defense mechanism
kill the compromised cells (antibody tags the antigen)
Innate immune response characteristics
- immune cells are non-specific (what should/shouldn’t be in the body)
- molecular components are non-specific: chemical mediators involved in an inflammatory response
- fast, immediate response
- no memory
Adaptive immune response characteristics
- immune cells are specific for each invader
- molecular components: antibodies and chemical mediators
- initial response takes a few weeks
- immunologic memory
Leukocytes involved in the adaptive immune response
- natural killer cells
- antigen presenting cells (dendritic cells)
- B lymphocytes
- T lymphocytes
B lymphocyte roles in an adaptive immune response
- recognize specific antigens that have invaded the body before
- secrete antibodies (plasma cells do this)
T lymphocyte roles in an adaptive immune response
- recognize the specific antigen presented
- turn into helper T cells & Cytotoxic T cells
Helper T cells role in an adaptive immune response
secrete cytokines to help coordinate the immune response
Cytotoxic T cells role in an adaptive immune response
Kill target cells that present a specific antigen
Natural killer cells role in an innate immune response
- target cells infected with viruses and cancer cells
- trigger apoptosis in these cells
Initiation of the adaptive immune response
- dendritic cell phagocytizes a pathogen for the first time
- breaks up the pathogen into small peptides
- travels to the lymph node and ‘presents’ an antigen (fragment of the pathogen) to T cells
- T cells differentiate in specific mature T cell and reproduce
- antigen-specific B cells develop and reproduce; target specific pathogen and also turn into plasma cells once exposed to antigen; plasma cells secrete antibodies specific to the antigen
- antibodies attach to the specific pathogen and mark it for destruction
Hypersensitivity reactions
immune system overreacts to cause damage instead of protection
Autoimmune disorders
immune system can’t distinguish between certain self- and non-self antigens
Immunodeficiency
the consequence of a defect in one or more components of the immune system
Immunocompromised condition
any condition that leaves your body vulnerable to infection because of an issue with the normal functioning of the immune system
Primary immunodeficiencies
inherited defect in the immune system
Secondary (acquired) immunodeficiencies
induced as a consequence of disease, treatment, or malnutrition (e.g. HIV)
Opportunistic infections
more often and more severe
