A/26-33 IMMUNPATHOLOGY (Tamer) Flashcards
how fast does type 1 hypersensitivity reaction occur?
occurs rapidly -within minutes
may be local and appear as an annoying response to hay fever (allergic rhinitis) or severly weakening the individual during asthma /in a fatal systemic disorder (anaphylaxis)
give the sequence of events during first exposure to allergen
- APC takes up the allergen and presents it via MHC 2 to CD4 + TH2
- When CD4+ TH2 cells are active they secrete cytokines and immunoglobulins. e.g. IL-4,IgE,IL-5,IL-13
- mast cells bind Fc portion of IgE
list the cytokines and immunoglobulins secreted during the first exposure to an allergen
CD4+ TH2 cells secrete :
IL-4 –> Specific B-cells –>IgE
IL-5-->Activates eosinophils
IL-13 –> Epithelial cells –> mucus secretion
what happens in the 2nd exposure to the SAME allergen ?
- allergen binds IgE on mast cells –>biochemical signals –>mast cells secrete the following :
- *Vasoactive amines :**
- Histamine
- Adenosine
- Proteases
- Kinins
LIpid mediators:
Primary:
- prostaglandins
- leukotrienes
*Secondary (late-phase reaction ,2-8 hrs later) :
-*
Neutrophils
-Lymphocytes
-Leukotrienes B4
-Eosinophils –>Release toxins to epithel–>necrosis
what are the two types of anaphylaxis ?
- systemic anaphylaxis
- local anaphylaxis
describe Systemic anaphylaxis
-due to protein antigen (bee sting) /drug (penicillin)
symptoms : itching , hives , skin erythema, respiratory difficulty , vomiting , diahrrea, abdominal crumps
-ARDS in the lung
practically we observe Laryngeal , ARDS, General **edemas
anaphylactic shock without intervention**
describe Local anaphylaxis and give at least 3 examples
- when antigen is limited within a particular site
e. g. - allergic rhinitis (Hay fever , home dust , animal hair)
- itching skin
- food allergy
- asthma bronchiale
Give the clinical picture of Asthma
chronic inflammatory disorder of the airways .
the asthma triad
1) reversible airway obstruction
2) airway inflmmation (bronchial)
3) bronchial smooth muscle hypertrophy, hyperressponsiveness
symptoms include : wheezing ,coughing,dyspnea,chest tightness
how do the pathology cock-sucking bitches classify Asthma?
The classification of Asthma is as follows :
1) extrinsic/atopic -70% of cases
type 1 hypersensitivity
2) intrinsic/non-atopic- 30% of cases
triggered by non-immune stimuli
e.g. aspirin, cold,psychological stress
pathogenesis of Asthma
-begins in childhood
1) first exposure to an allergen :
APC takes up allergen –> CD4+ TH2 cells secrete:
IL-4 –> Specific B-cells –>IgE
IL-5
IL-13
-IgE binds mast cells
——————————————————————————–
2) 2nd exposure to an allergen (allergen triggered asthma)
A) Acute immediate response
allergen binds IgE on mast cells –>biochemical signals –>mast cells secrete the following :
- *-Leukotrienes** C,D,E
- *-Prostaglandins** D2
- *-Histamine**
- Ach
- PAF
- these mediators open intercellular junctions–> more antigens enter airways and bind mast cells
- antigen directly causes vagal stimulation that leads to bronchoconstriction
- edema and mucus secretion are present
B) Secondary (late-phase reaction ,2-8 hrs later) :
mast cells release additional cytokines –> influx of other leukocytes , mainly eosinophils which then release protein toxins that amplify the response
asthmatic attacks are preceded by what ?
- allergic rhinitis
- urticartia /eczema
what are the most common antigens that cause Asthma ?
-dust
-pollen
-animal dander
(tiny particles of skin that had been shed from animals)
describe the micro-morphology of Asthma
“Always On TIME”
- Atelectasis (collapsed pulmn. parenchyma)
- Overdistention due to overinflation
-Thickening of the basement membrane
–Increases size of Mucus glands
-Mucus plugs in bronchi
(Cruschmann spirals /Charcot-Leyden crystals )
-Edema and inflammatory infiltration
clinical course of Asthma
air struggles to get out –> destruction of septa–> emphysema--> capillary diameter decrease–> more effort to pump blood out –> **cor pulmonale
more frequent attacks -higher risk for emphysema and cor pulmonale . aim is to prevent frequent attacks**
type 2 hypersensitivity - basic definition
caused by antibodies generated against endogenous/exogenous antigens
what are the consequences of type 2 hypersensitivity reaction
1) opsonization - cells are tagged with antibodies and are phagocytosed (IgG, c3b)
2) complement activation : via the classical pathway and formation of MAC
3) Antibody mediated cellular dysfunction :
*no cell injury/inflammation*
- Myasthenia Gravis - antibodies against Ach receptors –>muscle weakness
- Graves Disease- antibodies againsy TSH receptors–>hyperthyroidism
- RH-incompatibility -
Mom RH+ Fetus RH-
Blood Mix –>Antibodies Generated–> 2nd Child Screwed–> EDEMA, HYPOXIA , JAUNDICE ,ICTERUS
type 3 hypersensitivity reaction what means dat?
“systemic immune complexes disease”
include formation of antigen-antibody complexes and
their deposition in blood vessels and several organs (systemic) or in a particular organs (localized)
anitgens can be endogenous/exogenous
Pathogenesis of type 3 hypersensitivity reaction
ag-ab complexes formation in circulation –>
deposition in various tissues –>
inflammatory reactions and complement activation (c3a,c4a,c5a)
- complexes also cause platelet aggregation and activation of factor 12 (hageman) –> microthrombi
- ->ischemia
Name at least 3 diseases associated with type 3 hypersensitivity reaction
- reactive arthritis
- post strep. glomerulonephritis
- Systemic lupus erythematosus
- vasculitis
- Polyarteritis nodosa
descrive the micro-morphology of type 3 hypersensitivity reaction
- fibrinoid necrosis (protein deposition)
- microthrombi , ischemic necrosis
- acute inflammation
- fibrosis
Give and example of local immune complex disease
Arthus reaction -
results from acute immune complex vasculitis
inflammation and histologic appearance same as the systemic diseases but localized to one tissue/organ
How does a penguin build it’s house?
Igloos it together.
type 4 hypersensitivity reaction whats mean dat ?
T-Cell Mediated -Delayed Type Hyp.Sens
to which disease is the type 4 hypersensitivity reaction related to ?
Tuberculosis
pathogenesis of type 4 hypersensitivity reaction
1st exposure to bacteria
- APC presents bacteria via MHC 2 –> IL-12
- generation of TH1 and memory cells
2nd exposure
- recruitment of TH1 and memory cells –>secretion of IFN-γ
- macrophages secrete –> PDGF, TGFβ , IL-12 which further enhance the reaction causing Amplification Loop
is the Delayed Type Hypersensitivity reaction acute or chronic ?
Chronic -due to the amplification loop
(chronic unless the toxic agent is eliminated)
what can a prolonged DTH (type 4) reaction result in ? and why ?
Granuloma Formation
activated macrophages –> become epitheloid cells
–>fuse and form giant cells –>surrounded by lymphocytes–>Granuloma surrounded by fibroblasts and CT
describe the T-cell mediated response that occurs during type 4 hypersensitivity reaction
-APC present via MHC 1 to CD8+ T-cells –>become cytotoxic T-cells –> releases of Granzymes and Perforins–> apoptosis of target cell
I thought about going on an all-almond diet
But that’s just nuts
there are 2 facts regarding organ transplantation what are they ?
-recipient and donor have **different MHC
-**
donor cells go through Turn-Over (dying cells removed by phagocytosis) process in recipient’s body–>antigens presented as foreign
List 3 mechanisms of transplant ejection
1) T-cell mediated rejection
involves CD8+ T-cells of recipient and MHC 1 of donor
cytotoxic reaction against cell of the graft
2)Antibody mediated rejection:
dying donor cells release substances–>presented by APC’s MHC2 to CD4+ T-cells–>release of IL-4 IL-5–> Ag’s bind BCR–>B-cells become plasma cells –> Ab’s against graft cells
3)Delayed Type Hypersensitivity Rejection :
APC’s of Donor have MHC2 on them–>reconized by CD4+ T-cells –> differ. into TH1 –>release TNF, IFNγ
–>DTH reaction proceeds
List all the transplant rejection types
1) Hyperacute rejection
- *-minutes/hours**
- by pre-formed antibodies of recipient
- arteritis , arteriolitis
- thrombosis
2) Acute rejection
-weeks/months
A) Acute cellular -related with tubulitis ,CD4+,CD8+,Mononuclear cells –> all cause edema
3) Chronic rejection
-develops within **years
-**
doesn’t respond to immunosuppression
-charecterized by vascular changes(fibrosis) that lead to general ischemia in the organ
list at least 3 methods that improve graft survival
1) try to match between MHC of donor/recipient
2) immunosupression by corticosteroids/cyclosporins
3) Anti CD3 therapy - supress T-cell
4) interrupt costimulation B7-CD28 between APC and T-cell
What is the downside of Immunosupression?
increase the risk for viral infection
e. g.
* EBV,HPV,Herpes
what are the two types of transplantation
- organ transplantation
- Bone marrow transplantation
what are the two types of Bone marrow transplantation
1) Autologus:
- stem cells are from your own body
- hematopoietic disease is treated with chemo/radiation and disappears, then we take out stem cells so in case disease came back we repopulate them and transplant .
2) Allogenous - recipient recieve high doses of chemo/radiation for immunosupression since the stem cells come from a donor and might be rejected .
- rejection is mediated by T-cells and NK cells
what are the possible complications of allogenic bone marrow transplantation ?
1) GVHD (graft versus host diease)
immunosupressd patient doesnt reject graft but the organ transplanted recognizes (via T-cells of donor organ) the patient’s body as foreign -ALLAHU AKBARRRRRRR
-acute GVHD- epithelial necrosis in skin,liver,gut
- *-chronic GVHD**- Skin lesions that resemble systemic sclerosis and other changes that mimic autoimmune disorders
- *2) Immunodeficiency-** increased risk for infections
what is immunologic tolerance ?
ITS MEANENN -
a state of unresponsivness to an antigen that is induced by exposure of specific lymphocytes to that antigen
Self Tolerance what means dat ?
lack of immune responsiveness to one’s own tissue antigens
what are the two mechanisms that prevent self reactivity ?
- *1) Central Tolerance**
- deletion of self reactive T/B cells occurs
in the Thymus epithelial cells present self antigen with self MHC to T-cells
T-Cell recognized self-antigen? OK, U DIE
T-Cell bind MHC too strong ? OK, U DIE
(apoptosis)
same Process with B-cells in Bone Marrow . they can also go through receptor editing.
- *2) Peripheral Tolerance -**
to eliminate autoreactive cells that managed to escape
- Anergy: inactivation of lymphocyte by interferance in B7-CD28 costimulation
- Supression of T-cells by Treg via IL-10, TGFβ
- Activation induced cell death- T-cells that get stimulated repeatedly undergo apoptisis via
FAS-R
Mention genetic factors that may lead to autoimmune diseases
-Autoimmune diseases have a tendancy to **run in families
-**
connection between **HLA Locus/other Loci and autoimmune diseases
e.g.
HLA-B27–>**
Ankylosing spondylitis
NOD2-crohn’s disease