Module 2 Lecture 4: Immune System (Internal & External Defences) Flashcards
Why don’t B cells and T cells freely float around in the blood searching for pathogens?
B cells and T cells sit back and wait for pathogens to end up in lymph nodes.
* Lymphatic system drains tissues and the pathogens end up in lymph nodes where b cells and t cells will reside
* Activate only when the right antigen for them is found
What is meant by immunity?
Body’s ability to protect itself by resisting or eliminating harmful invaders
Immune system activities: Defends, Removes worn out cells and tissue debris, immune surveilance, hypersensitvity (ugly side of immune response)
What are bacteria and what are viruses
Bacteria: non-nucleated single celled organisms that cause tissue damage & disease via releasing enzymes
Viruses: DNA or RNA enclosed by protein coat which invades cell and injects it into the host
Viruses cannot carry out metabolic functions without host cell and it directs protein synthesis of virus when injected
What is this notion of virulence?
The inherent ability of a pathogen to cause disease
What are three external defences used against pathogens?
Mechanical, Chemical, Microbiological
Purpose of external defences is to not kill; rather protect it from entering
Examples of Mechanical Defence against pathogens?
- Tight junctions on epithelial cells which do not allow for the passage of pathogens
- Tears and cilia located in eyes/nose/oral cavity trap or fight off pathogen
Examples of Chemical Defence against pathogens?
Antimicrobial peptides in saliva and mucus are made all the time
A.K.A. host defence peptides
Examples of Microbiological Defence against pathogens?
Normal microbiota in our gut; the bacteria in our gut which will compete with the bacteria (pathogen) for space
* Make substances to prevent growth of other diseases
Mutual relationship with biota; bad biota however can lead to disease
What are the internal defences of our immune system?
Lymphoid tissue - Tissues that produce, store and process lymphocytes including:
* Bone marrow
* Thymus
* Lymph Nodes
* Spleen
* Tonsils
* Adenoids
* Appendix
* Peyer’s Patch
Spleen although it removes RBCs it plays an immune function by removing microbes.
Peyer’s patches are big concentration of lymphoid organs in certain areas like the gut for lymphocytes
Where are T-cells and B-cells formed?
T cells are formed at the thymus (site of maturational processing)
B cells are formed in the bone marrow
B cells and T cells only divide and expand in the lymphatic vessels or blood.
B and T cells circulate in lymphoid tissue
How do innate responses work?
Nonselectively defend against foreign material
* Rapid response but limited
Toll-like receptors - eyes of the immune system that sense and bind with telltale bacterial markers (distinguish normal cell from bacteria) and phagocytosis occurs
Innate defences include?
- Inflammation
- Interferons (cytokines; fights intracellular pathogens)
- NK cells (cell to cell action)
- Complement system (made by liver cells; innate immune function)
- Dendritic cells (bridge between innate and adaptive)
Dendritic cells use macropinocytosis and it’s innate receptors can identify what is a pathogen in what they just drank. Also, dendritic cells migrate to lymph nodes
How do adaptive responses work?
Selectively target particular invaders
What is humoral immunity and cell mediated immunity?
- Antibody-mediated immunity (humoral) is non cell-to-cell action; this involves **B cells in adaptive immunity that produce antibodies in the plasma **
- Cell-mediated immunity is another adaptive response which T cells follow; this is cell-to-cell action where **activated T cells are produced ** and leaves lymph nodes unlike B cells to fight off unwanted cells
In general, B cells recognize free-existing foreign invaders like bacteria, toxins and viruses. T cells specialize in recognizing cells gone awry and destroying them. (Different in recognition and response)
