11) Immunity Flashcards
what is a pathogen and how do they cause harm ?
- microorganism that causes disease.
- they produce toxins and cause damage to host cells & tissues.
what is immunity?
protection against disease provided by the body’s immune system
what is a non self antigen ?
- FOREIGN substance
- stimulates IMMUNE RESPONSE
- PROTEIN
what is an immune response ?
series of responses of body to the entry of a foreign antigen. Involves lymphocytes & phagocytes
what are 3 physical barriers to infection ?
- skin is a tough physical barrier consisting of keratin
● stomach acid (hydrochloric acid) which kills bacteria
● gut and skin flora – natural bacterial flora competes with pathogens for food and space
what are the 2 types of phagocytes ?
- neutrophil
- macrophage
where do phagocytes develop and store?
bone marrow
what do phagocytes do ?
remove dead cells & invade microorganisms by phagocytosis
state 4 facts about neutrophils.
- can squeeze through capillary walls into the tissues.
- released in large numbers from bone marrow during infection.
- short lived cells (die after phagocytosis).
- dead neutrophils often collect at site of infection and form pus.
state 4 facts about macrophages
- develop from monocytes (which travel round body in blood)
- kill microorganisms before they enter the blood.
- long lived cells.
- develop into macrophages when they leave the blood and settle in organs (eg lungs, liver)
give 6 steps of phagocytosis
- chemoattractants cause phagocytes to move towards pathogen = chemotaxis. pathogen binds to receptors on phagocyte membrane.
- receptors on phagocytes’ cell surface membrane recognise & attach tp chemicals on surface of pathogen.
- phagocytes engulf the pathogen to form a phagosome = ENDOCYTOSIS. Lysosome move towards the phagosome and fuse w it.
- Lysozymes & protease in the lysosome destroy ingested bacteria by hydrolysis of their cell walls. The process hydrolyses large insoluble molecules into smaller, soluble ones.
- soluble products from breakdown of pathogen are absorbed into cytoplasm of phagocyte.
- indigestible parts of bacteria are discharged from phagocyte by EXOCYTOSIS.
state 2 types of lymphocytes
- B lymphocytes
- T lymphocytes
give 4 differences between B and T lymphocytes
- B matures in bone marrow, T matures in Thymus gland.
- B is associated with humoral immunity involving antibodies, T is associated w cell mediated immunity (body cells).
- B make antibodies, T have cell surface receptors.
- Once mature, B can only make 1 antibody specific to antigen, T has diff receptor specific to antigen.
What happens to T cells after activated ?
- divide by mitosis
- release cytokines (stimulate macrophages to increase rate of phagocytosis)
- release cytokines to activated B lymphocytes to divide and develop antibody secreting plasma cells.
- stimulate T killer cells.
2 types of b lymphocytes ?
- plasma cells (secrete antibodies)
- memory B cells (involved in secondary immune response)
Outline the roles of T-lymphocytes in primary immune response
- activated by antigens
- specific to the antigen
- secrete cytokines
Outline the roles of B-lymphocytes in primary immune response
- production of memory cells
- antibody production
- plasma cells formed
describe what plasma cells do (B lymphocyte)
- secrete antibodies directly
- antibodies destroy pathogens/toxins.
- responsible for primary immune response.
- only survive for few days
describe what memory cells do (B lymphocyte)
- do not produce antibodies directly but circulate in blood & tissue fluid.
- if encounter same antigen later, develop into plasma cells.
- provide long term immunity = secondary immune response.
- live longer than plasma (sometimes decades)
How do B lymphocytes recognise non-self antigens
- antibodies on surface act as receptors
- these antibody receptors bind to the non-self antigen
outline the stage where hybridoma cells are formed
- cell membrane fuses
- spleen cells (plasma cells) fuse with cancer (myeloma) cells.
- hybridogen used in the process
outline the use of monoclonal antibodies in treatment of disease
- bind to specific antigens
- attach to enzymes
- drug for treatment can be activated
outline the procedure for producing mAbs suitable for use in another mammal
- inject hamster w antigen
- pick out the plasma cells which can make the antibody
- fuse these plasma cells with cancer cells (myeloma cells)
- hybridogen can be used
use of monoclonal antibodies in disease diagnosis
- locate position of blood clots
- locate cancer cells
- identify exact strain of virus
outline the events in an immune response (4)
- recognition of non-self antigens
- mitosis of B-lymphocytes
- development of plasma cells
- secretion of antibodies
what is active immunity (& artificial/ natural)
- antibodies produced by plasma when antigen enters.
natural : gained by being infected
artificial : vaccination
what is passive immunity (& artificial/ natural)
immunity gained without immune response (INTRODUCTION of antibodies)
- natural : mother to baby across placenta
- artificial : injecting antibodies
how do vaccines provide long term immunity
1) vaccine contains antigens that stimulate an immune
response
2) macrophages take up virus by phagocytosis and act
as antigen presenting cells (APC)
3) lymphocytes bind to these and under clonal selection
4) clonal expansion then occurs by mitosis
5) memory cells are formed
6) booster is used to further stimulate memory cell
formation
