Immunity
Cell recognition
-leukocytes = another word for WBCs
→ must be able to distinguish (tell the difference between) your own body cells (self) and
foreign cells (non-self) to prevent damage to host cell tissue
Recognising non self cells
-Pathogens and damaged / worn out cells have molecules on their surface that identify them
as non-self (phagocytes bind to these during non specific immune response)
-Other molecules are unique to that particular pathogen; these trigger the specific immune
response
-antigen = any molecule on cell surface membranes or cell walls that are recognised as
non-self (foreign) by the immune system and trigger/stimulate an immune response
-Antigens enable the immune system to
identify non-self cells such as;
-Pathogens e.g. HIV
-Abnormal body cells e.g. cancer cells
-Toxins
-Cells from other organisms of the same
species e.g. organ transplants
Recognising self cells
-a self marker (MHC) marks cells as self
Non specific defence mechanisms (innate response)
-non-specific as they are not activated in response to a particular pathogen
-triggered by disruptions to homeostasis
—> caused by cuts,worn out cells,damaged cells,surgery,pathogens
-chemical and physical barriers form part of non specific immune response (prevent
pathogens entering body)
Mechanism 1- phagocytosis
-phagocytes found in lymph nodes/specialised organs and tissues
-these include macrophages and neutrophils
Process:
1) phagocyte attracted to pathogen by chemical products produced by pathogen or
dead damaged abnormal cells → moves towards pathogen along conc. gradient
2) Phagocytes have receptors that bind to complementary molecules on surface of
abnormal cells
3) Phagocyte engulfs pathogen (endocytosis) to form a vesicle called a phagosome
, 4) Lysosomes move towards and fuse with phagosome - lysozymes released into
phagosome → enzymes hydrolyse large bio molecules into smaller ones
5) Soluble products are absorbed into cytoplasm of phagocyte or released by
exocytosis
6) Antigen presentation - the phagocyte (macrophages) present antigens on surface
(from pathogen) → activates T-lymphocytes
Lysosome = a spherical Golgi vesicle that releases lysozymes
Lysozymes = hydrologic enzymes used to digest abnormal cells and organelles
Exocytosis = outward bulk transport of materials through cell surface membrane
Cell mediated immunity
Specific immune response
-long term immunity (can protect against future infections)
-response is specific for unique antigens
-slower response due to need to clone specific cells
—> involves another type of WBC (lymphocytes)
2 parts:
-cell mediated response (T lymphocytes)
-humoral response (B lymphocytes)
-occur simultaneously
Lymphocytes
-B and T formed in bone marrow
-B mature/differentiate in bone marrow
-T mature in thymus gland → T helper cells and Cytotoxic T cells
-Tc kill abnormal cells and infected body cells
-produce protein called perforin which creates holes in cell surface membrane —> will
become freely permeable to all substances and cell will die
Cell mediated response (primary)
-there are lots of different T cells
-each type of T helper has thousands of copies of a unique antigen receptor on cell surface
membrane → complimentary to specific antigen so as a population , the T helper cells can
recognise almost any antigen
Process:
1) Antigen presentation
2) T helper cell with complementary receptor protein binds to antigen —> clonal
selection (only T helper cells with receptors for that antigen are activated)
3) T helper cell binds to antigen which stimulates T helper fell to undergo mitosis
(clonal expansion) —> clone of identical T helper cells produced
4) The cloned T helper cells differentiate into
Cell recognition
-leukocytes = another word for WBCs
→ must be able to distinguish (tell the difference between) your own body cells (self) and
foreign cells (non-self) to prevent damage to host cell tissue
Recognising non self cells
-Pathogens and damaged / worn out cells have molecules on their surface that identify them
as non-self (phagocytes bind to these during non specific immune response)
-Other molecules are unique to that particular pathogen; these trigger the specific immune
response
-antigen = any molecule on cell surface membranes or cell walls that are recognised as
non-self (foreign) by the immune system and trigger/stimulate an immune response
-Antigens enable the immune system to
identify non-self cells such as;
-Pathogens e.g. HIV
-Abnormal body cells e.g. cancer cells
-Toxins
-Cells from other organisms of the same
species e.g. organ transplants
Recognising self cells
-a self marker (MHC) marks cells as self
Non specific defence mechanisms (innate response)
-non-specific as they are not activated in response to a particular pathogen
-triggered by disruptions to homeostasis
—> caused by cuts,worn out cells,damaged cells,surgery,pathogens
-chemical and physical barriers form part of non specific immune response (prevent
pathogens entering body)
Mechanism 1- phagocytosis
-phagocytes found in lymph nodes/specialised organs and tissues
-these include macrophages and neutrophils
Process:
1) phagocyte attracted to pathogen by chemical products produced by pathogen or
dead damaged abnormal cells → moves towards pathogen along conc. gradient
2) Phagocytes have receptors that bind to complementary molecules on surface of
abnormal cells
3) Phagocyte engulfs pathogen (endocytosis) to form a vesicle called a phagosome
, 4) Lysosomes move towards and fuse with phagosome - lysozymes released into
phagosome → enzymes hydrolyse large bio molecules into smaller ones
5) Soluble products are absorbed into cytoplasm of phagocyte or released by
exocytosis
6) Antigen presentation - the phagocyte (macrophages) present antigens on surface
(from pathogen) → activates T-lymphocytes
Lysosome = a spherical Golgi vesicle that releases lysozymes
Lysozymes = hydrologic enzymes used to digest abnormal cells and organelles
Exocytosis = outward bulk transport of materials through cell surface membrane
Cell mediated immunity
Specific immune response
-long term immunity (can protect against future infections)
-response is specific for unique antigens
-slower response due to need to clone specific cells
—> involves another type of WBC (lymphocytes)
2 parts:
-cell mediated response (T lymphocytes)
-humoral response (B lymphocytes)
-occur simultaneously
Lymphocytes
-B and T formed in bone marrow
-B mature/differentiate in bone marrow
-T mature in thymus gland → T helper cells and Cytotoxic T cells
-Tc kill abnormal cells and infected body cells
-produce protein called perforin which creates holes in cell surface membrane —> will
become freely permeable to all substances and cell will die
Cell mediated response (primary)
-there are lots of different T cells
-each type of T helper has thousands of copies of a unique antigen receptor on cell surface
membrane → complimentary to specific antigen so as a population , the T helper cells can
recognise almost any antigen
Process:
1) Antigen presentation
2) T helper cell with complementary receptor protein binds to antigen —> clonal
selection (only T helper cells with receptors for that antigen are activated)
3) T helper cell binds to antigen which stimulates T helper fell to undergo mitosis
(clonal expansion) —> clone of identical T helper cells produced
4) The cloned T helper cells differentiate into
