Currently doing mod 7 - the 3rd line of defence is the most confusing and hardest thing ever and i feel like ive taken so much time on this
Does bio get harder than things like this? trying to decide if i should drop or not
nah not really. Also, that parts not too difficult once u have a fair understanding of it. Breaking it down in diagrams/flow charts or dot points helps.
Here's a section of my notes on that part.
The Third Line of Defence
The Adaptive Immune System
Antibody-mediated immunity
B Lymphocytes (B cell): B cells are produced in the bone marrow and are released into the blood. They reside in lymphoid tissues such as the lymph nodes and activate upon contact with a specific antigen. Upon contact, these B lymphocytes divide into either plasma cells or memory B cells.
Plasma cells
- Produce Y shaped antibodies which bind to specific antigens
- Antibodies do not destroy the pathogen, but interfere with its function.
- Antibodies either deactivate the pathogens active sites (neutralisation), bind to soluble antigens to form clumps of pathogen making it easier for phagocytes to destroy (precipitation), bind to antigens on the surface of cells (agglutination), or disarming pathogens by activating the complement system.
Memory B cells
- Provide the body with a long-term defence against pathogens
- Memory cells will recognise pathogens and produce plasma cells that make antibodies specific to the pathogen and its antigens. This leads to a faster, stronger and longer lasting immune response.
Cell-mediated immunity
T Lymphocytes (T cells)
- T cells are produced in the bone marrow and are released into the blood in an inactive state until contact with an antigen. The T cells bind to an antigen and procreates, then differentiates into one of four types:
- Cytotoxic (Cytokines)
These cells kill foreign and abnormal cells such as virus cells or cancer cells. They destroy cells by secreting or injecting toxic chemicals into the target cell, either killing the cell by breaking down its cell membrane or inhibiting replication.
- Helper (T Helper cells)
These cells promote the activities of other immune responses by increasing the activity of phagocytes, help promote inflammation, and stimulate the production of cytokines.
- Suppressor (Suppressor T cells)
These cells deactivate the immune response once the pathogen has been dealt with.
- Memory (Memory T cells)
These cells act similar to memory B cells, persisting after an infection to enable a larger and faster response to invading pathogens upon secondary exposure.
Immunity
Types of Immunity
- Active immunity
Active immunity occurs when your immune system is stimulated by an antigen to make its own T cells, B cells and antibodies. Active immunity is permanent as memory cells are produced.
Natural active immunity is when you become immune after catching a disease. The pathogen introduces the antigen to your immune system which triggers the adaptive immune system.
Artificial active immunity occurs through vaccinations which involve administering a controlled dose of antigenic material into the body which stimulates the immune system.
- Passive immunity
Passive immunity is when antibodies are transferred to an unimmunized person, providing them with temporary protection against a microbial agent or toxin. The body becomes immune after being administered these antibodies, but as the immune system is not activated, no memory cells are produced, providing only temporary yet immediate passive immunity.
Natural passive immunity occurs when a baby comes immune due to the antibodies it receives from its mother, through the placenta or breast milk.
Artificial passive immunity is when your body becomes immune after being injected with antibodies from someone else, such as the purified blood products of immune people or animals.
Primary and Secondary Responses to Infection
- understanding these graphs is crucial btw
Primary Immune Response
The primary immune response is when a pathogen enters the body for the first time. Because this is the first time that the immune system has seen this pathogen and its antigens, it can take a while for the matching T cells to be activated, and that there is a delay before the relevant B cells are also activated and matching antibodies produced.
Secondary Immune Response
The secondary immune response occurs after primary exposure.Because of the T and B memory cells produced in the first encounter, this enables a larger, stronger and after immune response upon reinfection with the recognised pathogen. The T cells will recognise the antigen and differentiate into cytokines, helper cells, suppressor cells, and memory T cells. The memory B cells will differentiate into plasma cells. Thus, the immune response and time of infection is quickly reduced.
