allergy Flashcards
what are 4 type of hypersensitive reaction/allergy and their mediator
- type 1: mediated by IgE
- type 2: mediated by IgG to word cell surface
-type 3: mediated by IgG to words soluble antigen
-type 4: mediated by T cells
what is allergy
is disyregulated immune system against other harmless antigen in our body/ environment.
in simple way: is when someone’s immune system reacted to substance/antigen that are harmless in our environment
what is atopy
genetic tendency/predisposition to develop allergy
what is allergen
is an antigen that triggers allergic response in individual
what is the mechanism of hypersensitivity type 1 of allergy
first protein/antigen is taken up by dendritic cells for antigen presentation to naive T cells
activation of T helper 2 cell will induce B cells switch
then B cells will produce IgE
IgE will bind to the Fc receptor of mast cells
then granules content of mast cells will cause the allergic symptoms
what is the mechanism for type 2 hypersensitivity allergy
hapten penicillin or antigen will bind to red blood cell surface.
this will stimulate production of IgG that will bind to the hapten and are recognized by NK cells and phagocyte that release toxin mediators that cause allergic reaction called hemolytic anemia
what is the mechanism for type 3 hypersensitivity allergy
when patient receive drug containing particles from other species and it cause decomposition of Ab:Ag complex causing aggregate in some tissue leading to leukocyte/immune system activation resulting in tissue injury
what is the mechanism for type 4 hypersensitivity allergy
hapten will bind to self-protein
dendritic cells will up take antigen/hapten and present it to Th1 cells which will then secrete pro-inflammation cytokines
what are two phase of ALLERGIC IMMUNE RESPONSES
- sensitive: sensitization and memory
- effector phase: immediate reaction and delay reaction
what is the mechanism of sensitization and memory phase
- allergen can have both T cells and B cells epitope
- allergen bind on dendritic cells which present allergen through MHC and TCR of naive T cells, it will be activated and differentiated into Th2 cells which will activate B cells.
or allergen with B cells epitope will directly bind to IgM on B cells - Th2 cells will differentiate into memory T cells
- B cells will under goes class switch to produce IgE
how does B cells undergoes class switch
If these activated B cells encounter specific signaling molecules via their CD40 and cytokine receptors (both modulated by T helper cells), they undergo antibody class switching to produce IgG, IgA or IgE antibodies (from IgM or IgD) that have defined roles in the immune system.
what is the mechanism of effector phase on immediate reaction and delay reaction
for immediate reaction: reapplication of hapten lead to local recruitment of hapten specific Th2 cytotoxic cells that will release cytokines and recruit other inflammatory cells which will lead to allergic symptoms like swelling.
delay reaction; is same as above but it delay to react this can be due to amount of allergen- specific IgE present or allergen dose
what is the mechanism of sensitization phase for type 4 hypersensitive
-first protein will bind to dendritic cells
-once dendritic cells encounter protein they will be mature and migrate into lymphoid tissue/vessels
-dendritic cells present antigen to T naive cells in lymph node
-naive T cells will be activated and differentiate into memory and effector T cells
- T cells will leave the lymph node and circulate in the blood for immune response
what is the mechanism of effector phase of delay reaction for type 4 hypersensitive
-first protein will bind to dendritic cells
-once dendritic cells encounter protein they will be mature and migrate into lymphoid tissue/vessels
-dendritic cells present antigen to T naive cells in lymph node
-naive T cells will be activated and differentiate into memory and effector T cells
- it takes T cells 1-3 days to move in lymph node and activate other inflammatory cells
what is dermatitis
is a common condition that causes swelling and irritation of the skin
