More Host defence Flashcards
what is an antigen
molecule capable of inducing an adaptive immune response
what do antigen presenting cells do
taste the environment, phagocytose foreign material, process and present antigen in lymphoid tissue
what are the properties of adaptive immune response
diversity and specificity, seld-tolerance, memory
describe the process of Tc cells
APC ingests bug, bug antigen and MHC molecule displayed on APC surface, CD8 cells activated and become cytotoxic, and bind to infected cells
perforin makes holes in the infected cell membrane and infector cell lyses
describe the process of Th cells
APC ingests bug, antigen displaced in APC surface with MHC2, interactions with cell receptor and co-inhibitory/ stimulatory receptors release cytokines, induces B cell activation and CD4 cells differentiated into specific Th subtype
where are MHC 1 molecules found
on all nucleated cells
where are MHC 2 found
only on macrophages, dendritic cells and B cells
what are B cells
type of lymphocyte involved in antibody production
where are B cells made and stored
made in bone marrow, stored in secondary lymphoid organs
describe IgM
secreted by immatured plasma cells, CSR; variable region unchanged, attached to different constant region so changed properties
good at neutralising/ agglutinating
looks like a ring
describe IgA
can access musocsal surface, mediates mucosal immunity, good at opsonising and fixing complement
double pronged
describe IgG
makes up > 80% of circulating antibodies
constant region can activate complement and interact with phagocytes
good at opsonising and fixing complement
describe IgE
binds mast cells
mediates allergic response
what is CSR
Class switch recombination; sequential excision of constant region DNA means same plasma cells secrete different class of antibody with same specificity
what controls CSR
cytokines
describe the effector function of antibodies
variable region binds to target antigen and constant region interacts with effectors
what causes chronic inflammation
irritating cause persists, cellular response is inappropriate, structural abnormalities
describe the pattern of chronic suppurative inflammation
mostly innate cells (neutrophils) often surrounded by capsule of chronic inflammatory cells/ fibrous tissue e.g. lung abcess
describe the pattern of chronic autoimmune inflammation
mostly cells of adaptive immune system, may lead to fibrosis e.g. rheumatoid arthritis, smoking leading to fibrosis
describe the pattern of chronic granulomatous inflammation
mostly cells of adaptive immune system, may lead to fibrosis caused by infection, foreign body, aberrant inflammation, unknown origin e.g. sarcidosis
what is a granuloma
small nodule composed of organised collection of macrophages surrounded by dense collection of lymphocytes and fibroblasts
what is a hypersensitive reaction
disease where immune response to environmental antigens causes inflammation and damage to the body itself
what is a type 1 hypersensitivity reaction
IgE; immunological memory to something leading to allergic response
- immediate and acute
- e.g. acute anaphylaxis, hay fever
describe what happens during a type 1 hypersensitivity reaction
allergen binds to IgE coating mast cells in skin
mast cell contain granules that contain mediators that active immune system e.g. histamine, cytokines, basophils
binding of mast cells to IgE links them and signalling pathway made so they degranulate
what is the classification used for hypersensitivity reactions
Gell and Coombes
what is a type 2 hypersensitivity reaction
IgM/ G bind to cell surface antigens
- fairly quick
- leads to tissue injury and altered receptor function
- e.g. transfusion reactions, autoimmune disease
what is a type 3 hypersensitivity reaction
immune complexes leading to activation of complement
- antibodies and targets circulate, little lumps of antibodies and target get deposited in skin/ lung/ kidneys etc leading to activation of immunity and tissue damage
- e.g. farmers lung, SLE, post-streptococcal GN
what is a type 4 hypersensitivity reaction
T cell mediated delayed type hypersensitivity (DTH)
- formation of granulomas so slow process
- depends on activation of T cells which secrete cytokines when activated by antigens
- e.g. TB, contact dermatitis
how to remember hypersensitivity reactions
ACID allergic cytotoxic killing immune complexes delayed T helper cells
what is inflammation
local response to infection or injury
what is the main function if inflammation
destroy/ inactivate foreign invaders, set the stage for tissue repair
what are the key mediators in inflammation
phagocytes
what are the basic stages of inflammation
bacteria introduced, Chemomediates cause vasodilation and capillary permeability
chemoattractants recruit neutrophils to area
diapedesis results in neutrophils entering tissue where they engulf and phagocytose bacteria
capillaries return to normal as neutrophils continue to clear infection
what initiates acute inflammation in the lungs
specialist tissue resident macrophages = alveolar macrophages
how do alveolar macrophages start the process of inflammation in the lungs
respond to pathogens etc by recognising PAMPs and DAMPs
what type of reaction is anaphylaxis
type 1 hypersensitivity reaction
atopy definition
genetic tendency to exaggerated IgE response to antigen
