week 2 immunology Flashcards
what are the characteristics of the innate immune system
- non-specific
- distinguishes between human cells and pathogens but not between different types of pathogens
- fast and immediate
- no memory
what are the characteristics of the adaptive immune system
- highly specific
- distinguishes between different pathogens based on antigens
- slower: can take a few days to develop
- immunological memory
what are the two subcategories of innate immunity
cellular - phagocytes - eosinophils, mast cells - basophils (in that order) humoral - complement system - cytokines (happening simultaneously)
what are neutrophils
- phagocyte
- most abundant white blood cell
- they contain granules that are filled with many destructive enzymes such as peroxides, alkaline and acid phosphates which are responsible for kill and destroying bacteria and other pathogens
what are monocytes
- phagocyte
- bigger than neutrophils (can engulf more)
- in blood
- macrophages when in tissue
what do macrophages do
macrophages break down pathogens, process antigens and present these antigens to T cells and antibodies
- they are antigen presenting cells (APCs)
what are the stages of phagocytosis
- movement of the phagocyte toward the microbe
- attachment of microbes to phagocyte surface
- endocytosis of microbe and formation of phagosome
- fusion of phagosome with lysosome
- killing of microbe through digestion by enzymes
- discharge of waste material
what are eosinophils
- help combat parasitic infections
- involved in allergy and asthma
- granules contain many enzymes
what are basophils
- least common of the white blood cells
- contain large granules with inflammatory mediatiors
- no proven function
- found in parasitic infection
what are cytokines
- part of the humoral category of the innate immune system
- they are small proteins secreted by both immune and some non-immune cells in response to stimulus
what do cytokines do
- they communicate with other cells
- they bind to specific receptors on these cells producing a signalling molecule that leads to many biological effects
- they are key players in innate and acquired immunity: differentiation, activation, chemotaxis, enhancing cytotoxicity
what is humoral immunity
- AKA antibody mediated immunity
- involves helper T cells and B cells
- category of the adaptive immune system
what is cellular immunity
- involves phagocytes, cytotoxic T cells, cytokines and chemokines
- part of the innate immune system
what is the development process of lymphocytes
- production of B and T cells usually takes place in the bone marrow
- when they are maturing T cells gain T cell receptors and B cells gain B cell receptors
- activated by reaction with pathogen
what is the role of the lymphatic system
- drainage of tissue
- absorption and transport of fatty acids and fats
- immunity
what are the components of the lymphatic system
- lymphatic vessels
- lymphatic organs (primary and secondary)
what are the primary lymphoid organs
where blood cells are produced and receive their ‘early training’ (acquire ability to interact with antigens)
- bone marrow
- thymus
what are red blood cells, platelets and myloblasts formed from
myeloid stem cells
what do myeloblasts go on to become
granulocytes
- eosinophils
- basophils
- neutrophils
what are the steps of erythropoiesis (red blood cell formation)
- pluripotent haematopoietic stem cell
- uncommitted stem cell
- committed progenitor cell
- erythroblast
- reticulocyte
- erythrocyte
where is the site of T cell maturation
- T for Thymus
cortex = mature T lymphocytes
medulla = immature T lymphocytes and macrophages - so mature as they move through the thymus
what are secondary lymphoid organs
sites of lymphocyte activation by antigens
- lymph nodes
- spleen
- mucosal immune system
- tonsils
what is the red and white pulp in the spleen
red pulp: filter for ageing/damaged red blood cells, basically filters blood and removes particles like microorganisms
white pulp: mainly contains lymphocytes
where is the site of production for T and B cells
bone marrow
where is the site of maturation for T and B cells
T cells = thymus
B cells = bone marrow
where is the site of activation for T and B cells
secondary lymphoid organs
what are the adaptive phases of the immune system
- recognition of danger
- production of specific weapons (antibodies and cytotoxic T cells)
- transport of weapons to site of attack
what are cytotoxic T cells
T lymphocytes with CD8+ receptors
(T cell receptor only recognise antigens when CD8+ is bound to MHC I)
- killing!!!
what are helper T cells
T lymphocytes with CD4+ receptors
(T cell receptors only recognise antigens when CD4+ is bound to MHC II)
- Stimulate B cells to produce antibody
how does a cytotoxic T cell work
- cytotoxic T cell binds to infected cell
- perforin makes holes in infected cell’s membrane and enzyme (granzymes=enzyme that can promote apoptosis) enters
- infected cell is destroyed
what is the role of Th1 (T helper 1)
activates macrophages
defining cytokines: IFN-gamma
role in disease: autoimmunity, chronic inflammation
host defence: intracellular pathogens
what is the role of Th2 (T helper 2)
eosinophil and mast cell activation, alternative macrophage activation
defining cytokines: IL-4, IL-5, IL-13
role in disease: allergy
host defence: helminths
what is the purpose of MHC I
- found on virtually all nucleated cells
- present ‘virally induced’ peptides to CD8+ T cells and triggers cytotoxic response
what is the purpose of MHC II
- found only on ‘professional antigen presenting cells’ (i.e macrophages)
- presents exogenously produced antigen to CD4+ T cells
what are B cells
- involved in humoral activity
- main function is production of antibodies
where are B cells produced and where do they mature
bone marrow
what happens when B cells are activated
- activated when reaction with pathogen
- on activation they are differentiated into plasma cells (responsible for antibody production) or some stay as memory B cells
what are antibodies
proteins that are produced as an immune response against antigens
different antigens induce the production of different antibodies
what are the two regions is antibodies
- antigen binding region (the two bite at top of Y) (FAB)
- lower region (stem of Y) is called Fc region
what are are the five classes of antibodies
- IgM
- IgE
- IgA
- IgD
- IgG
what does IgM do
first antibody to be produced in infection
what does IgE do
- defends against parasites
- causes allergies
what does IgA do
protects mucosal surfaces
resistant to stomach acid
think A for acid
what does IgD do
unknown function
IgD signals B cells to be activated
what does IgG do
most common type
by binding of many kinds of pathogens it protects the body from infection
- there is placental transfer of IgG
what are the three functions of antibodies
neutralisation
opsonisation
complement activation
what happens in neutralisation in antibodies
prevention of attachment and entry mostly IgA (GI tract and respiratory tract)
what happens in opsonisation in antibodies
macrophages
what happens in complement activation in antibodies
classical pathway
what is the complement system
consists of more than 30 proteins/factors that are found in the plasma, present in inactive form
- part of the humoral category of the innate immune system
what are the three complement system pathways
- alternative pathway
- classical pathway (antibodies)
- lectin pathway
how are the proteins in the complement system activated
activated in a cascade
activation of the complement takes place on the surface of target cells
what are the functions of the complement system
- direct lysis of target cells
- some products increase blood flow and act as chemo-attractants and recruit other immune cells to the site of infection to enhance the immune response (inflammation)
- other products facilitate and enhance phagocytosis (opsonisation)
how does the complement system work
- binding of complement proteins to microbial cell surface or antibody
- formation of C3 convertase
- cleavage of C3
- formation of C5 convertase
- then at the end you end up with formation of membrane attack complex (MAC) (pore on surface of cell)
what happens when MAC makes pores in complement system
pores on cell surface confuse osmosis as liquid leaks out and cell dies
what is active immunity
protective immunity against pathogen induced by host’s own response to that pathogen
- takes time to develop
- b memory cells present
- permanent/long term protection
what is passive immunity
the transfer of antibodies or lymphocytes specific for the microbe
- immediate
- b memory cells absent
- protection is temporary
