Immune System Flashcards
Immune system
Group of cells, tissues, organs, mechanisms that defend an organism against pathogens and other foreign substances
Immune response
Complex series of specific and non specific processes involving a range of cells and chemicals
If the body successfully fights infection, will respond more quickly, effectively if encountered again
Non specific defence mechanisms
Physical barriers
Chemical barriers
Phagocytosis
Physical barriers
Skin (keratinised), impermeable
Mucociliary escalator in airways
Chemical barriers
Sebum, antibacterial fatty acids, pH 5.4
Tears, lysosomes, destroys bacterial cell wall
HCl, gastric juice, lactic acid, vagina
Phagocytosis
Inflammatory response, phagocytes, chemicals
Phagocytosis, phagocytes (intracellular chemicals)
Blood clotting, haemostasis
Specific defence mechanisms
Cell mediated response Humoral response (body fluids)
Specific immune response
AP immunity, TB cells (lymphocytes, WBC)
Phagocytosis
Phagocyte attracted to pathogen due to chemicals released by it
Moves towards pathogen up con grad
Phagocyte has several receptors on its cell surface membrane that attach to chemicals on the pathogen surface
Lysosomes within phagocyte migrate toward phagosome, formed by engulfing bacterium
Lysosomes releases lysozyme into phagosome where bacterium is hydrolyse
Hydrolysis products of the bacterium absorbed by phagocyte
Humoral immunity in blood
Pathogen/ toxin enters bloodstream, encounters many B lymphocytes
Some B cells have appropriate molecule on surface, attach to antigens on the surface of pathogen/toxin
Attachment=> rapid div of B cell, form plasma cells, clones of original
B cells produce appropriate antibody
Some become memory cells, remain in body for long time
Antibody effects
Neutralisation
Precipitation
Agglutination
Complement reaction
Neutralisation
Antibody combines with active part of toxin, prevents it from attaching to the surface of body cell
Precipitation
2 binding sites on 1 antibody may link with 2 molecules of antigen to produce a lattice like immune complex
Soluble antigen molecules may be precipitated and more easily ingested by phagocytes
Agglutination
Similar to precipitation, 2 binding sites may bind to 2 different pathogens
Leads to phagocytosis
Complement reactions
Series of reactions which lead to lysis of pathogen or phagocytosis
Cellular immunity
T cells have highly specific receptor molecules on cell surface which attaches to antigens
Only happen if antigen on surface membrane of one of body’s own cells, next to chemical marker (Major histocompatibility complex proteins)
Invaded cell will present antigens on surface
Only T cell triggered, divides rapidly, form clone T cells
Types of T cell
Cytotoxic
Helper
Memory
Cytotoxic T cells
Destroy target cell, usually the body’s own cell infected by viruses
Involved in destruction of cancer cells
Helper T cells
Stimulate more Tc and B cells to divide, produce plasma cells
Memory T cells
In future infections of same antigen
Antibodies
Protein called immunoglobulins
Produced by plasma cells, derived from B lymphocyte
Specific to antigen
Has antigen binding site Variable region Constant region Heavy chain All held together by disulphide bridges
Immunity
Primary response
Primary response, initial delay. Time taken for complementary specific B cells to randomly collide with antigen, bind, divide, form plasma cells, release relevant antibodies
Antibodies destroy antigens, fewer random collisions, antibody conc falls
Immunity
Secondary exposure
Rapid secondary response due to memory cell prescence
More likely to collide with antigen. Initiate IR
More plasma cells, more antibodies
Immunity
Between primary and secondary response
Conc of antibody does not go back down to 0
Memory cells remain
Antigen variability
Due to genetic mutation, antigens on pathogen surface frequently change shape
Multiply more rapidly, mutate quickly
Slow immune response to make new antibodies
Potentially risk vaccines being ineffective
Vaccinations
Preparation of antigen from pathogen
Injected or swallowed, depending on type
Methods of vaccine production
Dead pathogen, cholera
Toxins, produce less harmful toxoids, tetanus
Weakened pathogen, polio
Genetically engineered Eukaryotes producing required antigen, Hep B
Herd immunity
Vaccinate significant proportion of population provides protection for unvaccinated individuals
Difficult for disease to spread, fewer people to infect
Important for people who cannot be vaccinated, old people, babies, immune deficient people
Can lead to eradication of disease
Active immunity
Immune system responds to antigen, produces specific antibodies in response to antigen
Natural, encounter disease normally
Artificial, vaccination
Passive immunity
Person given antibodies
Natural, breastmilk
Artificial, tetanus when person given antibodies for immediate effect
Viruses
Not living
Acellular, no cell structure, cytoplasm or membrane
Genetic material core surrounded by capsid (made of capsomeres)
Outer envelope of lipoproteins
HIV structure
Spherical shape Lipid, glycoproteins envelope Cone capsid 2 identical RNA strands Has reverse transcriptase Retrovirus
Methods of transmission of HIV
Body fluids mix
Blood transfusions, sexual intercourse, IV drug use, needle sharing, mother to baby through placenta
HIV replication, infection
Enters bloodstream, circulates
HIV binds to CD4 protein on Th cell membrane
Capsid fuses with membrane, RNA and enzymes enter cell
Reverse transcriptase, virus RNA converted into DNA
DNA inserted into Th nucleus
New DNA creates mRNA with cell enzymes, contain instructions for viral proteins, RNA
New visions made in cell, break out with piece of cell membrane, forming lipid envelope
AIDS
State of immune system infected with HIV
HIV can be latent
AIDS develops when virions interfere with normal Th function
If Th damaged, no stimulation of B to replicate, produce antibodies
Memory cells infected, destroyed
Body cannot respond appropriately to infections, superinfections will kill
So many Th killed, system cannot recover
HIV treatment
No cure, control with antiretrovirals
MOnoclonal antibodies
Produced from 1 cell
Specific action, 1 antibody type produced
Polyclonal antibodies
Humoral response, more than 1 antibody produced as microbes have more than 1 type of antigen on surface
Each antigen stimulates production of specific corresponding antibody from different B cell
Use of monoclonal antibodies
Target cancer cells with toxic drugs, does not kill healthy cells
Monoclonal antibody function
Requires production of antibody that binds to antigen only on cancer cells
Attach to cytotoxic agent
Inject antibody cytotoxic complex into patient, target cells
Benefits of monoclonal antibodies
Only a small amount of cytotoxic agent required
Fewer side effects
Problems with monoclonal antibodies
MCA produced in mice, mice protein is foreign, immune response mounted against it
Overcome by use of GM mice, produce antibodies that have similar structure to human antibodies
Postcode lottery
Uses of monoclonal antibodies
Herceptin Heart disease Colon cancer Leukaemia Non Hodgkin lymphoma Suppress immune system in transport operations
Production of monoclonal antibodies
Antigen inserted into GM mouse Isolate antibody forming cells Tumour cell + antibody forming cell = hybridoma Antibody producing hybridoma cloned Form monoclonal antibodies
ELISA test
Enzyme linked immunosorbent assay uses antibodies and colour change to identify substance
Diagnostic tool
ELISA test
Description
Antigens from sample attached to surface
Antibody with enzyme conjugate applied over surface so it can bind to antigen
Enzyme substrate added
Reaction produces colour change in substrate
Uses of the ELISa test
Determine serum antibody concentrations
Detecting food allergens
Serological blood test for coeliacs
Certain classes of drugs
