Adverse immune reactions (year 2) Flashcards
what are the four types of adverse responses?
tolerance or breakdown or tolerance
autoimmunity
hypersensitivity
transplantation
what is tolerance?
state of unresponsiveness to a particular antigen
when is tolerance useful?
essential to prevent immune reactions to the bodies own tissue
what cells must show tolerance and where is this generated?
T cells generated in the thymus
B cells removed by bone marrow if they are self-reactive
what occurs if tolerance isn’t selected for?
autoimmunity
what is autoimmunity?
loss of self/non-self discrimination in the immune responses causing damage to host tissue
what may induce autoimmunity?
exposure of hidden antigens new epitope formation cross reactivity with microorganisms viral induction immunoregulation deficiency damage to immunologically privileged sites
name some immunologically privileged sites
brain, reproductive tract, eye, bile ducts
name two systemic autoimmune diseases
systemic lupus erythesmatosus
rheumatoid arthritis
what are the 4 types of hypersensitivity?
type 1
type 2
type 3
type 4
what is a type 1 hypersensitivity?
atopy - allergic condition
IgE is produced to an antigen
describe how a type 1 hypersensitivity comes about
can be from an issue with class switching from IgM to IgG/A that goes wrong and switches to IgE IgE binds to mast cell stimulating histamines and inflammation
what is a type 2 hypersensitivity?
when antibodies bind to antigens on host cells
what causes tissue damage during type 2 hypersensitivities?
phagocytosis and complement
give an example of when a type 2 hypersensitivity may occur?
blood group mismatch
foals RBCs leak into mares circulation, mare forms antibodies, foals ingests these antibodies in colostrum
what is a type 3 hypersensitivity?
immune complexes form/deposit on host tissue
why do type 3 hypersensitivities occur and what is the outcome?
due to an excess of antibody
this activates complement and cause granulocytes to release enzymes
give an example of type 3 hypersensitivity
glomerulonephritis
immune complexes are deposited in the glomerulus
what is type 4 hypersensitivity?
T cell mediated so doesn’t involve antibodies
how does a type 4 hypersensitivity occur?
primed T cells respond to chronic antigen load by production of cytokines which attracts and activates macrophages causing damage to the tissue
give an example of when a type 4 hypersensitivity is used
TB testing
what is the main cause of transplant rejections?
differences in MHC between donor and host
what are the four types of transplant?
autograft
isograft
allograft
xenograft
what is an autograft?
from the same animal
what is an isograft?
from a genetically identical animal
what is an allograft?
from the same species
when is a xenograft?
from a different species
