Third line of defence Flashcards
what are the characteristics of the adaptive immune response?
It is highly specific: able to recognise and respond exclusively to antigens
immunological memory: cells ‘remember’ antigens after initial exposure, allowing a larger and faster response upon re-exposure
what cells are the adaptive immune response carried by?
white blood cells called B and T lymphocytes
what is the function of B cells in the adaptive immune response?
B cells help perform main role in the humoral immune response. B cells are activated and secrete specific antibodies (immunoglobulins) which circulate in the blood stream and target specific non-self antigens in the extracellular space
What is the function of T cells in the adaptive immune response?
T-cells perform main role in the cell mediated response, targeting host cells infected by pathogens, such as virus. Antigens from the virus is presented to the T-cell and this instruct T cell to induce the virally infected cell to die. This prevents virus replicating and T-cells can also kill cancerous cells or transplanted cells
what is the crossover between innate and adaptive immune systems?
T-cells are activated through cytokine exchange with APCs and naïve B cells are activated by cytokines released by T-helper cells
what is humoral immunity?
occurs in the blood and lymph where antibodies produced by lymphocytes, are secreted onto extracellular fluid. Humoral immunity responds to extracellular pathogens and involves B cells and antibodies.
what is the clonal selection theory in the humoral response?
non-self antigens act as selecting agents and activates correct naïve b cell, initiating humoral immune response
why can adaptive immune response recognise and response to millions of unique non-self antigens in the humoral response?
In the lymph nodes there are millions of naïve b cells with 10^5 unique antibody like receptors and complementary antigen binding sites
what happens when a complementary b cell is selected?
when a corresponding naïve b cell is selected by a non-self antigen, the naïve be cell proliferates, making clones of itself and then the clones differentiate into memory B cells and plasma B cells.
what happens after proliferation and differentiation of B-cells
-Plasma B cells secrete antibodies with the same antigen binding site as original antibody receptor on naïve B cell. Antibodies flood the blood stream and perform their function at infected site
What results in immunological memory of humoral response?
memory B cells have the same antibody surface receptors as naïve b cell but can survive a lot longer than plasma B cells- which leads to long term immunity. If the same pathogen with the same antigens invade, the memory cells in blood stream will recognise it and response will be faster and stronger
characteristics of naïve B-cell
- have receptors similar in structure to antibodies and identify antigens through their Ig like receptors binding to them
- there are specific naïve B cells for specific antigens therefore, different pathogens
characteristics of plasma B cell
- plasma B cells perform main role of humoral immune response
- plasma B cells result from naïve B-cells being activates and undergoing clonal expansion
- produce antibodies against antigen that activated the naïve B-cell
- antibodies are released into the bloodstream
- survive for only a few days
what are a antibodies called and what are they made of?
antibodies are known as immunoglobulins and are made up of proteins
How are antibodies produced?
antibodies are produced by plasma B-cells
characteristics of antibodies
- antibodies target and bind to specific non-self antigens that are in the extracellular space
- They will have the same antigen binding site as the original cell surface receptors on the original naïve B cell
- they can be find bound to the plasma membrane of B lymphocytes or floating freely in extra cellular spaces
what is the structure of antibodies?
- antibody is composed of 4 polypeptide chains: two heavy and two light chains forming a Y-shape. At the end of each arm, there is the same antigen binding site made up of both a heavy and a light chain. - The two chains making up the binding site are known as the variable region.
- the variable region is specific and only matches to one antigen
- the constant region is below the variable region and is the same for all antibodies
- the constant region has functions such as activating complement proteins and binding to phagocytes
- The heavy and the light chains are held together by disulphide bonds
what is an antigen paratope?
it is the antigen binding site on antibodies which is complementary to a specific antibody epitope
what are the benefits of hinge region of antibodies
it increases flexibility and improves efficiency in antigen binding and cross linking during agglutination
what is the function of the variable region on antibodies?
- it has a specific shape to select a specific antigen and allow antibodies to bind to different antigens
- it is the antigen binding site between the antigen and antibody
- the two binding sites are identical to each other on each arm of the Y shape
how do antibodies have such variety?
variable portion of antibodies have relatively small number of genes that are cut and shuffled randomly to produce millions of different combinations. This allows random production of innumerable antibodies