Adaptive immunity Flashcards
What does the adaptive immune system recognise from the innate immune system response that triggers its activation?
Antigens presented on cells.
What is the difference between a bacterial and a viral infection?
Bacteria do not hijack cells (there are exceptions like Anthrax but it’s rare), they can live independently.
Viruses need a cell to survive however. It uses a cells capability to produce proteins to replicate.
What are some innate immune mechanisms against viruses?
If a cell is infected with a viral protein it will release a cytokine called Type-I interferons (IFN). This reacts by binding to all adjacent cells to protect them from viral infection.
What are natural killer cells?
These can kill infected cells. It must happen in the presence of other mediators produced by the adaptive immune system. natural killer cells provide non-specific immunity.
Over the course of an infection, what increases in terms of immune components?
You only recognise changes in immune components after about a week of an infectious state. The adaptive immune components produced to eradicate and protect against future infections include antibodies and cytotoxic T cells.
What are cytotoxic T cells?
They will eventually kill all infected cells, even if they are self-cells. They can recognise infected cells with foreign material.
Where are antibodies produced from?
B cells, antibodies hit their peak about 10 days after infection.
How long after an infection do specific cytotoxic T cells hit their peak?
After about a week
Why does the adaptive immune system take a long duration to be activated?
The body must first ensure it is attacking a foreign material before it initiates an immune response. Memory cells are what speed up this process.
There is also an essential innate immunity coordination to the adaptive immune system that needs to take place. E.g., phagocytes, macrophages, natural killer cells, interferons, complement fragments and other innate immune system components. These all need to break down foreign material to form antigens and present them on their cells, they travel up the lymph nodes to naive T cells in the lymph.
What happens when an APC comes into contact with a T cell?
Every naive T cell has different T cells receptors capable of recognising specific antigens to its receptors. All naive T cells have different receptors that correspond to different antigens. When a compatible receptor and antigen bind the naive T cell will become activated. This will proliferate T cells so that it can migrate out into the body and start killing foreign material.
THE ONLY WAY TO ACTIVATE A T CELL IS TO PRESENT AN ANTIGEN ON AN MHC MOLECULE.
What is an MHC molecule?
This is major histocompatibility complex.
The function of MHC molecules is to bind peptide fragments derived from pathogens and display them on the cell surface for recognition by the appropriate T cells.
Without MHC you are invisible to your immune system. Your T cells will not be able to recognise you or antigens correctly. This can be a form of cancer where certain cancers down regulate the MHC markers so there is no appropriate display of antigens.
WITHOUT AN ANTIGEN BEING PRESENTED BY A MHC T CELLS DO NOT FUNCTION. THEY ARE REQUIRED TO ACTIVATE AN ADAPTIVE IMMUNE RESPONSE.
Everyones MHC molecules are unique to them, allowing us to identify our own cells. T cells can recognise our self and non-self MHC molecules presenting antigens. This is essential for organ transplant surgeries.
How are B cells activated and what do they do?
B cells do not need a specific antigen to be presented to it like T cells. B cells also have the capability to phagocytose pathogens. B cells have a molecular marker of CD20
B cells have antibodies on its surface capable of binding to a pathogens antigens on the pathogens surface. The antibody and the pathogen have to be compatible just like in T cells. The binding will cause proliferation that produces antibodies.
B cells can differentiate into antibody producing plasma cells.
What do T helper cells do?
T helper cells have a molecular marker CD4
They work by activating cytotoxic T cells and produce antibodies.
Without the helper T cells the immune system will not work.
What do Cytotoxic T cells do?
Cytotoxic T cells have a molecular marker of CD8
They eradicate viruses or infected and tumour transformed cells.
How many T cells are able to recognise any one antigen?
Approximately 16. Only 16 T cells distributed around your body have the capability of recognising any one specific antigen. These 16 naive T cells need to have the capability to proliferate within 6 days and produce thousands of these T cells to fight the infection. After they’ve fought the infection they die as activated T cells cannot exist with nothing to do: apoptosis.
Memory T cells are produced along the entire process. This process cannot take place without the innate immune system.
