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
