8 Hypersensitivities (1 Hour) Flashcards
Type 1 hypersensitivities are mediated by
Ab
What hypersensitivity is atopic?
Type 1
What cells are immediately activated in Type I responses?
Mast, eosinophil, basophil
What receptors facilitate Type 1 hypersensitivity?
FC(epsilon)
Mast cells are found
In skin and mucosa
What is the high affinity Fc receptors for IgE found on Mast cells called?
Fc(epsilon)RI or CD23a
What do IL4 and IL13 stimulate?
Th2 response
What, from mast cells, stimulates and promotes eosinophil activation?
IL3, IL5, GM-CSF
What does CCL3 do?
Attracts monocytes, macrophages, and neutrophils
What does IL-5 induce on eosinophils?
FC(epsilon)RI
What is in high number during chronic allergic inflammation?
Eosinophils
What is the major contributor to tissue damage?
Eosinophils
What has the same mechanism as histamine but lasts longer and has stronger action? Who makes it?
Leukotrienes
Eosinophils
What is the most potent leukotriene? What do they do?
LTB4
They increase capillary permeability and increase mucus production
What causes class switching of B cells?
IL4
What does IL4 increase on cell surface of leukocytes?
VCAM-1 for adhesion
What cells have Fc(epsilon)R
Basophils and mast cells
What are the properties of allergens?
They require a tiny dose, they are very stable and can exist for a long period of time, small and highly soluble
What is the first exposure to an allergen? What happens?
Priming
No allergic reaction
How are allergens taken up?
They diffuse across mucosal epithelium and are processed and presented by Th2 and B cells make IgE against them
These IgE bind to Fc(epsilon)RI on mast cells
What happens immediately in an acute atopic response?
Cross linking of mIgE
Degranulation of mast cells
Sneezing, congestion, pruritis, rhinorrhea
What happens in the late phase of atopic responses?
After 4-12 hours there is an influx and activation of eosinophils, neutrophils, basophils and Th2
10 fold increase of mast cells w/ increased Fce receptors
What happens in atopic asthma?
Contraction and relaxation of smooth muscle in bronchioles
What causes systemic anaphylaxis?
Allergens introduced directly into the blood, systemic act. of mast cells, increase in vascular perm., huge drop in BP
What are Type 2 hypersensitivities called? What do they react against?
IgG or IgM against cell surface or ECM
What causes damage in Type 2 HS?
Complement binding (binds to both IgG and IgM)
NK through ADCC
In Type 2 HS, Ab against cell surface are ___________ but Ab against internal Ag are ____________
Pathogenic, non-pathogenic
What causes the bystander damage during Type 2 HS?
Phagocytes want to connect to the cells and phagocytose them but they can’t so they release lytic particles “at” the cells causing widespread damage
What is a penicillin “allergy?” What does penicillin bind to?
It is a Type 2 HS
the penicillin binds to the surface of RBC and gets lysed because it is recognized as non-self
What type of HS are transfusion reactions?
Type 2
What is given to protect fetal RBC from maternal Ab in second pregnancy?
Rhogam, it prevents B cell activation to Rhesus factor
Anti CD20 is used in
B cell non-Hodgkin’s lymphoma
What is anti-CD52 used in?
Chronic B & T cell leukemias
Immunosuppressants for BMT
What are Type 3 hypersensitivities known as?
Immune complex
What do Ab react to in Type 3 HS?
Soluble Ag
This happens when there is too much Ab and not enough Ag
How do Type 3 cause acute inflammation repsonse?
Phagocytes can’t chew up complexes so they release enzymes at the cells and the cells are damage and release internal contents, this leads to DAMPs and resultant activation
Rheumatic fever is caused by what? What does it react to?
Streptococcal cell wall Ag
This is similar to the heart wall and we get cross reactivity
What causes myasthenia gravis?
Anti-Ach receptor Ab
What causes grave’s disease (hyperthyroidism)?
Antibody stimulates TSH binding to receptor and you get overactivation of thyroid
What causes SLE?
Ab against nucleic acids, nucleoproteins
What does SLE cause?
Nephritis, arthritis, and vasculitis
What causes serum sickness?
Type 3 HS against various components of whole blood
What do Type 2 and 3 HS have in common?
They are both Ab mediated
Complement is major mediator in both
What are Type 4 HS also called?
Delayed type HS
What mediates DTH?
Ag-specific CD4
What are the 3 types of DTH?
Contact (Ni, poison ivy, latex)
Tuberculin (Tb test)
Granulomatous (look for presence of granulomas)
What are the two stages of DTH?
Sensitization
- antigen uptake by DC
- present on class 2 HLA
Elicitation
- recruit CD4 T cells
- pro-inflammatory cytokines
- Th1 cells
What is a quick and dirty way to measure cell mediated immunity?
Reaction of CD4 to something you know they were previously exposed to
What causes granulomatous DTH? What T responds?
Intracellular organism able to resist macro killing, macro walls it off with several layers, can form necrotic center, associated with Th1 response
happens in Tb
What causes MS
Type 4 HS against myelin proteins
What causes RA?
Type 4 HS in joints
What causes IDDM?
Type 4 HS against pancreatic islet ag
