Week 9 - Anaphylaxis Flashcards
- What are the key features of innate immunity?
- Neutrophils eat pathogens and send off signals
- Monocytes are triggered to turn into pathogen-eating macrophages
- Eosinophils attack parasite
- Basophils contain granules filled with histamine and other compounds related to allergies
All instant, on demand immunological defence system
- Explain the basics of Phagocytes:
Soldiers of immune system, responsible for killing and digesting invading microbes.
- Microphages: start in bone marrow, constantly circulate in blood, cannot replicate
- Macrophages: start as monocytes in stem cells in bone marrow, not as numerous as micro, but live longer
- What are the key features of Acquired immunity?
Lymphocytes begin a more specific and enduring attack - killer T cells, helper T cells and B cells.
- B cells produce antibodies capable of producing lasting immunity
- T cells coordinate immune system response
- Killer T destroy virus-infected cells
- What is Humoral immunity?
B cells - secrete antibody after antigen exposure
- What is Cell mediated immunity?
T cells - helper, suppressor and cytotoxic
- What is the Complement system?
Form of innate and acquired immunity - comprised of collection of proteins that recognise proteins on cell walls of invading microbes - invading bacteria are marked with chemicals that make them stand out
- What are cytokines?
Messengers
Help other elements of immune system to work together
- Explain the basics of the inflammatory response:
Phagocytes are activated, producing cytokines that activate other cells of immune system - cascade of reactions follows
- primary physical effect is for blood circulation to increase around affected area
- blood vessels around site dilate, gaps appear in capillary walls allowing larger cells of blood to pass through
- immune presence is strengthened
- painful due to expansion of tissues, causing mechanical pressure on nerve cells
- Explain the function of Mast cells:
Granules found in loose connective tissue - primary facilitators of both inflammatory and immune responses
- When damaged or activated by antigens they released their contents into interstitial fluid - release histamine, neutrophil chemotactic factor, eosinophil chemotactic factor and produce leukotrienes and prostaglandins.
- Explain the process once mast cells are activated:
- Histamine is a vasoactive amine - temporarily and rapidly constricts large vessels, dilates post capillary venules and retracts endothelial cells of the capillary walls
2/3. Chemotactic factors attract WBC to destroy dead tissue and toxins and release histaminease that limits the runaway effect of histamine - increase capillary blood flow and cap permeability - Leukotrienes - similar effects to histamine - stimulate slower and longer response than histamine
- Prostaglandins - several forms, Type E associated with inflammation, act on smooth muscle and increase vascular permeability, suppresses histamine release - responsible for the long-term pain of inflammation - Aspirin/NSAIDS suppress PG-E synthesis
- Define:
- Antigen
- Antibody
- Allergen
- Allergic
- Anaphylaxis
- Antigen = any substance when introduced into tissues/blood induces formation of antibodies and reacts only with its specific antibodies
- Antibody = protein produced by certain cells in presence of specific antigen - combines with antigen to neutralise/inhibit/destroy it
- Allergen = antigen that provokes a hypersensitivity reaction
- Allergic = sensitive to an allergen
- Anaphylaxis = severe, life-threatening, generalised or systemic hypersensitivity reaction, characterised by rapidly developing life-threatening airway, breathing, circulation problems, with skin/mucosal changes
- What is the mechanism of anaphylaxis?
- Prior sensitisation to an allergen
- Interaction of allergen with specific IgE immunoglobin antibodies - leads to activation of mast cells and release of preformed mediators stored in granules
- Mediators cause capillary leakage and mucosal oedema resulting in shock and asphyxia
- What is the role of adrenaline in anaphylaxis Rx?
Actions:
1. Beta 1 adrenergic - positive inotrope - raise BP, positive chronotrope - raise HR
2. Beta 2 adrenergic - bronchodilatation
3. Beta adrenergic - increase cAMP production which decreases inflammatory mediator release
For pt on beta blockers - give glucagon which increases production of cAMP and makes adrenaline work better
- What are the side effects of adrenaline?
- Feeling of impending doom
- Cardiac arrhythmias - SVT, VT, VF
- Marked hypertension - transient thumping headache, risk of intracerebral bleed
- Increased myocardial oxygen demand - may lead to angina/AMI
These are rare and usually only when administered IV
- What are the roles of these drugs in anaphylaxis?
- Steroids
- Anti-histamine
- Steroids - may prevent or shorten reactions - take up to 4-6hrs to be maximally effective - limited role in acute mx
- Antihistamines - primary role in non life threatening allergic reactions - urticaria; may prevent or shorten reactions but should never be relied upon as first line treatment
