Adaptive Immune System Flashcards
Lymphocyte proliferation
T helper cell
- MHC class II molecule
- Macrophages release interleukin wich stimulates T cells
- CD4 molecule helps the T cell receptor bind to the MHC II molecule to bind to present antigen
- After the presentation the T helper cell secreates Interleukin 2 which stimulates the binding of the receptor with the antigen
- Daughter cells divide again if presented with complementory antigen
Lymphocyte Proliferation
B cell
- Can be activated by T helper cells
- Presented on the cell surface membrane by MHC class II molecule co-stimulated by CD4
- T cell receptor binds to MHC class II to form antigen complex which is co-stimulated by ILs from T helper
- Stimulated B cells to divide
- Some differentiate into plasma cells to produce antibodies
Structure and function
Antibodies
- Bind to extracellular antigens
- Y shaped protien molecule with 4 polypeptide chains
- 2 heavy chains and 2 identical light chains
- Variable region has the binding site and constant region
Types of immunoglobin
IgM pentameter - shaped like a hexagon
IgA Dimer - 2 antibodies connected by heavy chain
IgE monomer - Long heavy chain
IgG - monomer
Primary response
- First exposure to antigen
- B cell undergoes several divisions
- Forms plasma cells and memory B cells
- Plasma cells produce antibodies
- Symptoms can be observed when pathogen have enough time to cause tissue damage
- After antigen destroyed antibodies degrade and plasma cells die
IgM
Secondary response
- Previously exposed to antigen so memory B cells quickly divide to form plasma cells
- Quickly produce antibody so makes more memory cells
- Quicker to produce antibodies so more plasma cells/antibodies
- Memory cells persist for long time
IgG
Effect of antibodies
- Inactivate antigen
- Activates Complement Cascade
- Initiates release of inflammatory mediators
- Facilitate Phagocytosis
- Antibody dependent cellular activity
Stage 1
Inactivate antigen
Effect of antibodies
antibody binds to an antigen or when many antigens are bound together
Stage 2
Activates Complement Cascade
Effect of antibodies
Antigen binds to antibody. Antibody can then activate complement proteins inflammation, attracts WBC and lyses cells
Stage 3
Initiates release of inflammatory mediators
Effect of antibodies
Antibody binds to mast cell /basophil. Triggers degranulation
Stage 4
Facilitate Phagocytosis
Effect of antibodies
Antibody binds to antigen. Macrophages attaches to Fc of the antibody and phagocytoses both the antibody and the antigen
Stage 5
Antibody dependent cellular activity
Effect of antibodies
Activates cytotoxic cell responses. Cytotoxic cells release chemicals that destroy the antibody-bound antigen
Funtion of Immunoglobulin
IgG
- Secondary immune responses
- Some maternal IgGs cross the placental membrane
Funtion of Immunoglobulin
IgA
- External secretions
- Saliva, tears, intestinal and bronchial mucus, breast milk
Function of Immunoglobulin
IgE
Target gut parasites and are associated with allergic responses
Funtion of Immunoglobin
IgM
- Primary immune responses
Funtion of
Cell mediated Immunity
- Intracellular effects in response to pathogens, allergic reactions, tumours
- Essential Viral infections as antibodies can’t cross into cell
- Destroys infected/affected cell
Process of
Cell mediated Immunity
- Viruses infect cells
- Some viral proteins are broken down and become processed antigens
- Combined with MHC class I molecules & presented on surface
- T-cell receptor binding with the MHC class I to activate by Surface molecule CD8
- Secreation of IL2 by T-Helper cells stimulates T cells to divide
Funtion of
Cytotoxic T cell
- Attract innate immune cells such as Macrophages and stimulates Phagocytosis of antigen/cell
- Inflammatory response
- Activate additional cytotoxic T cells
- Directly kill virus infected cells
- Viral antigens on surface
- T cells bind to the antigens on the surfaces and cause the cells to lyse or under go apoptosis
Active Natural immunity
- Antigens are introduced through natural exposure
Active artificial immunity
- Antigens are deliberately introduced by a vaccine
Passive natural immunity
- Antibodies from the mother are naturally transfered to her child across the placenta or in milk
Why do allergic responses occour?
- Immune response to a non-pathogenic antigen
Allergen is an antigen that is typically not harmful to the body - Sensitive individuals that have an inappropriate immune response
- Sensitivity or hypersensitivity to the antigen
- Immediate hypersensitivity reactions are mediated by antibodies
- Sensitisation and Re-exposure Phase - same as primary response phase
Process of
Allergic response
- Antibodies IgE and IgG are produced
- IgE antibodies are immediately bound to mast cells and basophils.
- Memory T and memory B cells formed Re-exposure
- Allergen binds to IgE already present on mast cells
triggers immediate release of histamine, cytokines, other mediators - Cause allergic symptoms strong and rapid response
Aging Immune system
- Remove fluid from tissues,
- Absorb lipids from the digestive tract
- Remove defective red blood cells
- Thymus replaced with adipose tissue so lose the ability to produce mature T cells and may lose functionality
- Antigen exposure leads to fewer helper t cells
Less stimulation of B and cytotoxic T cells - Antibody and cell mediated responses decrease
- Primary and secondary antibody responses decrease
