Lecture 13/14: Support and defence system Flashcards
What are the various lines of defence? what type of defence are they?
Nonspecific defence (inniate immune system):
- First line: nonspecific physical and chemical surface barriers
- Second line: Nonspecifc internal cellular and chemical defense
Specific defence:
Third line: immune response
NOTE: if pathogen penetrates first defence then goes to second and if survives second goes to third
What are examples of the first line of defence?
- tears: proects against substances in eyes
- skin: physical barrier to outside
- Large intestine: normal bacterial inhabitants prevents invaders
- Saliva: washes awa microbes
- Respiratory tract: mucus traps organisms
- Stomach: acid skills organisms
- Bladder: urine washes microbes from urea
What are examples of second line of defence?
- identify foreign matter but isnt specific, doesn’t develop memory
- defensive cells, protein,s inflammation and fever
Explain protein based defence
- called lysis
- mainly in liver, released in inactive form
- deactivated by native proteins
- become activated by: polysaccharides on bacteria surface or antigen/antibody complexes (adaptive immune response)
- acts in digestive way, creates holes and fluid rushes in causing invader to burst
- in brain has similar system made from glial cells
- complement attacks the plaque and neurofibrillary tangles (common for alzheimers and neurodegradation)
How does inflammation workq
- foreign object found
- histamine is released
- capillaries opened, inc blood flow carrying defence cells and chemicals causing redness
- heat due to inc in metabolic rate
- swelling due to fluid containing defensive chemicals
- pain prevents movement allowing it to heal
- can also occur as response to tissue damage, stress, arthritis, obesity
How does a fever work?
- infection or toxins cause release of monocytes/macrophages then **pyrogenic cytokines
- gets into hypothalamus and resets thermoregulatory point
- why you get hot
How does the support and defence system defend against more than just invading microbes
- part of CNN, SDS always on doing multiple things and is “watching” for invaders
- protects against local tissue damage not due to infection
- normal tissue turnover (cell death, regeneration during wound healing
- appearance of transformed cell populations (cancer)
How does the support and defence system relate to obesity?
- adipocytes increase number (hyperplasia) but also in size HYPERTROPHY
- cell gets too big for capillaries and oxygen cant get to it
- lead to reduced blood flow/hypoxia and cell death
- Macrophages infiltrate these areas, recruited by kind of stress signal (MCP-1)
- macrophages release inflammatory peptides such as TNF, IL-6 that cause insulin resistance in surrounding tissues such as muscle
How can insulin resistance in small amounts be beneficial for SDS and obesity
- insulin promotes glucose uptake
- dont want tissues to take away energy, want tissues to get it
- if it becomes chonic and constant macrophages can lead to diabetes
Where do macrophages infiltrate?
- areas of reduced blood flow/hypoxia
- adipocytes
skeletal muscle (in obese individuals)
What are parenchymal cells
- think “parent”
- functional cell, are the critical functional portion of the tissue (gland/organ)
ex: liver, skeletal muscle, heart, brain, adipose tissue, pancreas
What are stromal Cells
- non parenchymal cells
- framework and support for parenchymal cells
form support and defence system
ex: neurons, astrocytes, fibroblasts, stem cells, gap junctions
What stromal changes occur during the development of pancreatic cancer
increase in sensory and SNS nerve fibers, macrophage infiltration, capillary density
What is MHC
major histocompatibility complex
- like a flag pole, holds an antogen that is either self or non self
What is an antigen
a molecule often on surface of a pathogen that the immune system recognizes as a specific foe
How does memory in the support and defence system work?
1) invader enters body
2) macrophage encounters, engulfs and digests the invader
- macrophage places a piece of invader (antigen) on its surface with the MHC marker
3) Alert: macrophage presents the antigen to a helper T cell and secrets a chemical that activates the T cell
4) alarm: activate T cell (effector helper T cell)
- activates into either naive cytotoxic T cell or a naive B cell
** slide21 of lec 13/14
How can T cells detect a foreign antigen
- cannot detect if circulating freely in the body
- must be displayed on a MHC.
- ability to trigger a T and B cell response to foreign antigens requires macrophages
What happens to the Helper T cell once it is activated?
- turns into effector helper T cell (means activates) it can either
1) turn into Naive B cell - building specific defences, cell divides
- plasma cell secretes antibodies targeting pathogens or toxins outside of cells
- like missile response, is not direct
2) turns into naive cytotoxic cell - builds specific defences and turns into effector cytotoxic cell
- targets cells infected with intracellular pathogen (cancer cells/cells of organ transplants)
- finds cells displays foreign antigen, kill by chemical means (perforins punching holes in target cell membrane like compliment)
- engages directly
How does memory play a role in subsequent encounters with pathogins
- memory B cells and memory cytotoxic cells are created
- first exposure to antigen will often get sick
- second exposure has a much stronger response to antigen because of memory cells
How is negative feedback involved with T cells
- T suppressor cells suppress activation of immune system, particularly production of T helper cells
- Too little T suppressor response: association with autoimmune disease, allergies, graft rejection, inflammatory bowel disease
- too much T suppressor response: possible connection to cancer and increased incidence of infectious diseases
How are glial cells used for protein based defence?
- glial cells in brain recognize neurofibrillary tangles and plaque (brains form on compliment)
- tangles and plaque are characteristic of alhziemer’s disease leading to neurodegredation
What are neutrophils
- type of phagocyte
- first on scene and consume bacteria
- method of cell based defence
What are macrophages
- phagocytes
- consume almost anything
- method of cell based defence
What are Eosinophils
- discharge enzymes that digest
- non phagocytes
