Immunity Flashcards
What is the immune response?
a process to respond to a foreign antigen involving the activation of lymphocytes and the production of antibodies
Primary non-speficic denfence
-same response irrespective of type of pathogen/ first or second attack
-Prevents invasion by pathogen
Skin
-physical barrier that is difficult to penetrate.
-The keratinised protein of dead cells of the epidermis are tough and imprevious
-Production of sebum inhibits growth of pathogens
-Antimicrobial proteins disrupt strucutre and fucntion of microbial cell membranes
Blood cotting
Break in skin is a potential entry point but clotting forms placelet plug to seal wound
Tears
Contains lysozymes which destroy bacteria & fungal cell walls
HCl
Secreted in stomach lining: acidic so destroys pathogens
Mucous membranes
-e.g. nasal passages, vagina, trachea etc
-Goblet cells secrete mucin-> mucus
-Mucus traps organisms and also contains lysozymes which destroys bacterial and fungal cell walls
Inflammation
-mast cells are activated in damaged tissue
-They releasde histamines, serotonin, prostoglandins and cytokines
-Vasodilation of arterioles & capillary walls become more permeable-> increased blood flow into area and incresed tissue fluid formation
-Cytokines attract phagocytes to wound
-Heat, redness, tenderness, swealling, pain
Phagocytosis
{phagocytes = neutrophils + macrophages}
-Pathogen produces chemicals & damaged cells release cytokines
-Phagocytes are attracted to cytokines & toxins, thus moving down chem conc gradient by chemotaxis
-Phagocyte recognises a foreign protein on pathogen
-Pathogen attaches to receptors on CSM of phagocyte
-Phagocyte engulfs pathogen via endocytosis into a phagosome
-Phagosome fuses with lysosomes to form a phagolysosome
-Lysosomes contain hydrolytic enzymes (e.g. lysozyme) whihc destroys pathogen
-Hydrolysed products are absorbed by the phagocyte
Macrohages phagacytosis
-After digesting a pathogen, its antigens are presented on the surface of the macrophage and becomes an antigen presenting cell
-These exposed antigens can now stimulate other cells in the specific immune response
-Macrophages are formed from differentiated monocytes
Cytokines
-Chemicals produced by phagocytes that engulf pathogen
-Act as cell-signalling molecules
-inform other phagocytes that the body is under attack
Opsonins
Chemical; that bind to pathogens and tag them so that they can be recognised by phagocytes
Specific immune response
-triggered by surface antigens and targets specific types of pathogens
Lymphocytes
-small WBC, congregate in lymph nodes
-Are inactive until they come in contact with antigen-> activated, undergo mitosis to form larger clones
-Gain cell surface receptors during the maturation process
Where are T cells produced and Matured
Bone marrow and then Thymus glands
where are B cells produced and matured
BOTH bone marrow
What are the 4 types of T cells?
-T helper cells
Receptors bind to APC
detect antigens and secrete cytokines
Thus stimulates production of T cells, stimulate activity of B cells, stimulates macrophages to ingets pathogens
-T killer cells
Destroys infected cells by producing chemical which makes a hole in the pathogens CSM
-T memory cells
remain and ciruclate in the blood
Co-ordinate response on reinfection by dividing by mitosis to produce T killer
-T regulatory cells
Supress immune system e.g. inhibit ig production in B lymphocytes
Stop immune response once pathogen is eliminated
Make sure body recognises self-antigens
what is the function of B cells? what are the 3 types?
to search for the antigen that matches their receptors (clonal selection)
stimulated by T helper cells to divide in clonal expansion
-B effector cells: divide by mitosis to form plasma cell clones
-Plasma cells: Produce Ig to a specific antigen
-B memory cells- provide immunological memory-upon reinvasion, divide by mitosis to produce huge numbers of plasma cells
Antigen
A protein on the surface of a pathogen which triggers an immune response
Cell mediated immunity
-Immune response that does not involve antibodies
-Macrophages engulf pathogens by phagocytosis and become APCs
-Receptors on T helper cells are complementary to antigens on APCs
-They bind together- clonal selection
-T helper cells become activated and produce cytokines
-These stimulate more t cells to divide rapidly by mitosis- clonal expansion
Cloned T cells then: develop into T killer cells, cytokines stimulate phagocytosis and B cells to divide, develop into T memory cells
Humoral Immnunity
(B cell activation)
-When a pathogen enters the body, B lymphocyte with complementary Ig binds to it & processes it to form APC.
-Activated T helper cells bind to B lymphocyte APC (clonal selection) & activate it to form activated B lymphocyte
-These divide by mitosis into plasma cells & B memory cells (clonal expansion)
-Cloned plasma cells secrete Ig, disable the pathogen
This is a primary immune response- can take 7-14 days to become fully effective and lasts 2 weeks
Secondary immune response upon reinfection- early and rapid
Plasma cells have a higher number of:
-mitochondria, provide ATP for Ig synthesis
-Ribosomes, inc protein synthesis to produce Ig
-Golgi, RER etc
Antibodies
-specialised Y shaped glycoproteins called immunoglobulins
-Quarternary structure- made from 4 ppc chains, 2 heavy, 2 light
-Heavy chains held by disulfide bridges
-Constant region- binds to host cell, same for all ig
-Variable region- 2 antigen-binding sites: they are antigen specific
How ig works
produce antitoxins, by causing clumping to aid engulfing by other macrophages, by precipitation of soluble antigen s
Mantoux test
-TB
-Tuberculin injected below skin
-If Ig present, skin becomes inflamed and redness appear
-Size of red area is measured
-Large= strong immunity, small=limited, no mark= no immunity
HIV 2 tests
-Point of care test
Finger brick or mouth swap
result within 11-28 days
test takes 20-40 mins
Unreliable
-Blood sample
detects present of ig and antigens
results within 2-14 days
More accurate and fewer false +/-
Allergies
-when the immune system responds inappropriately to a harmless allergen
-Produce antibodies to the allergen
-Allergen triggers an immune response
-IgE produced, binds to complementary receptors on mast cells (asymptomatic)
-Upon re-infection, allergen binds to IgE attached to mast cells
-Releases histamine, triggers inflammatory response
what are antibodies
soluble glycoproteins that bind to complementary antigens on the surface of the pathogen
why is a secondary immune response more effective than primary immune response?
-Memory cells remain in the blood for long periods of time
-During secondary infection, recognise antigens on the pathogen
-More rapid clonal expansion
-Increased production of antibodies
-Secondary response is faster
what is sensitisation?
initial contact with the allergen triggers the primary immune response
what is the difference between natural and artificial active immunity?
natural = primary immune response to natural infection to a pathogen
artificial = deliberate introduction of antigens to stimulate primary immune response (i.e. vaccination)
what is active immunity?
activation of B and T lymphocytes in response to the presence of pathogenic antigens, resulting in the production of antibodies and memory cells
what is passive immunity?
no activation of lymphocytes and no memory cells produced
presence of antibodies ONLY
