Adaptive Immunity and Disorders - Part 1 Flashcards
(38 cards)
What is the adaptive immune system
part of your immune defense that learns to recognize and remember specific pathogens (like viruses or bacteria) so it can respond more effectively if they invade again
What are characteristics of the adaptive immune system
- Specific (tailored to microorganism)
- Complex form of immunity (has memory)
- Delayed response
- Develops upon exposure (adaptive and acquired)
What are the 2 main branches of the adaptive immune system
- Cell mediated immunity
- Humoral Immunity
What is cell mediated immunity
- Involves the activation of activation of certain immune cells to combat pathogens
- Provided by T lymphocytes
Involves
- Helper T cells (CD4+) – help B cells make antibody and help activated cytotoxic T cells
- Killer or cytotoxic T cells (CD8+) – kill infected cells or tumour cells
- T regulatory cells (FoxP3+) – suppress immune responses
Where are dendritic cells located
sentinel (guard) cells located at ‘frontiers’ of the body (physical and chemical barriers that protect the body e.g. skin, mucous membrane, tears, saliva, stomach acid, good gut bacteria), and they migrate to lymph nodes when they capture antigen
Where are macrophages located
located in lymphoid organs connective tissues
Were are lymphocytes located
- 2% circulate in blood, rest are located in lymphoid organs
What are antigens
Antigens are molecules that your immune system can recognize as foreign. They may be surface molecules or secreted by pathogens.
These foreign substances trigger the immune system to generate antibodies which are then used to target and neutralize the antigens.
e.g.
- Bacterial antigens – toxins, cell wall proteins, flagella, enzymes
- Viral antigens – envelope proteins, enzymes
- Blood group antigens
- Histocompatibility antigens on organ cells
- Molecules on pollen grain surfaces
What are antibodies (Ab)
Also known as immunoglobulin
Antibodies are Y shaped proteins produced by B cells in your immune system which recognize and stick to antigens to help the immune system find and destroy invaders. Each antibody matches one type of antigen like a lock and key.
- Made by plasma cells
- Circulate in blood
- Exposure to Ag induces the production of antibodies
- Antibodies bind to antigens
What is IgM
First antibody released after infection
What is IgA
Found in saliva, sweat, mucous, milk, intestinal secretions
What is IgD
B cell surface receptor
What is IgG
Most abundant (75-80%)
What is IgE
Associated with allergy, chronic worm infections
What are different functions of antibodies
occurs when antibodies bind to their specific antigen
Inactivates by:
- neutralisation
- agglutination
- precipitation
Fixes and activates:
- complement
What is antibody neutralisation
When the binding of an antibody to its antigen on the surface of a virus will inhibit it from being able to attach and enter its target
What is agglutination
antibody binding to antigens on cells (eg. red blood cells) can lead to agglutination reactions. Each arm of the antibody can bind to a different cell bringing them into proximity. When enough cells have clumped together the clumps become visible. This will lead to cell lysis.
Antibodies cause large particles (like cells or microbes) to clump together. Which helps trap and immobilize pathogens - and make it easier for phagocytes to eat them.
What is antibody causing precipitation
antibody can bind to soluble molecules (like toxins) making them form insoluble complexes that fall out of solution. These can be eliminated by phagocytic cells.
. As each antibody can bind to two different antigens and the antigens have multiple binding sites, clumps can form. This will increase the visibility of the antigen to phagocytes and promote phagocytosis.
How do antibodies activates the complement system
Antibody binding to its antigen will activate complement
this will lead to formation of the membrane attack complex and cell lysis and will enhance phagocytosis and inflammation
How is the adaptive immune response initiated
- Lymphatics carry antigen and cells carrying antigen into lymph node (major site of antigen presentation and generation of adaptive immune responses)
- Antigen in blood drains into spleen
What cells can be antigen presenting cells
- Dendritic cells in connective tissues and epidermis
- Macrophages in connective tissues and lymphoid organs
- B cells
Dendritic cells phagocytose pathogens and enter lymphatics to present the antigens to T cells in lymphoid organs.
What are antigen presenting cells and their function
A special immune cell which initiates the adaptive immune response (cellular) by
- capture an antigen
- Process it by breaking it into small pieces
- Preset those pieces on their surface using Type 2 MHC (major histocompatibility complex) proteins
- When a T helper cell (CD4+) encounters an APC its TCR binds to the MHC class 2 molecule binding to the specific antigen fragment which is the first signal that activates the T helper cell
*T cell will only bind the antigen if its receptors are specific for the antigen
What are MHC molecules
Major histocompatibility complex molecules also known as human leukocyte antigen (HLA)
MHC molecules are a group of molecules found on the surface of cells that recognize foreign invaders, and their primary function is to present small fragments of proteins called antigens to immune cells.
What is a MHC Class 1
- Found in all nucleated cells – so every cell except a red blood cell
- Function is to present endogenous antigens (antigens that come from inside the cell e.g. virus) to the surface of the cell to give to cytotoxic T cells (target and destroy infected or abnormal cells)
