M: Immunopathology 1 - Week 5 Flashcards
How does the adaptive immune system rely on the innate?
relies on the innate immune system to facilitate T cell signals, that are required to mature the APCs
Explain in 4 steps the process of recognising and removing an infectious agent
- Resident APCs within peripheral tissue recognise or endocytose small peptides of foreign antigent (macrophages or other innate cells might also engulf pathogen)
- APC (and macrophages) mediate the activation of T cells
- Antigen presented to T cells activates them and in turn activates B cells to produce antibodies
- Depending on the antibody, a particular range of mechanisms will be used to fight off the infection
What mechanisms are used to fight off infection when the following antibodies are produced? A) IgM and IgG B) IgG C) IgA D) IgA, IgG, IgM
A: C” activation
B: Opsonisation
C: Block adherence
D: Toxin neutralisation
How can T cells affect host tissue?
Some of the T-cell responses can cause cytotoxicity to the resident host cells (epithelial cells)
What T-cell enables chemotaxis of inflammatory cells to the site of infection/injury?
T-helper cells secrete cytokines and chemokines that enable the chemotaxis
What T-cell can dampen down the immune response?
Treg (Regulatory T cell)
Describe 2 broad ways immunopathology can occur, and provide an example for each
- Failure of all or part of the immune system
- e.g. immunodeficiency - Abnormal or unwanted responses
- e.g. allergies, autoimmune disease, graft rejection
Compare Primary vs Secondary Immunodeficiency for the following:
A) Cause
B) Rarity
A:
Primary - results from “inherent congenital defect” in the immune system. Caused by either genetic or intrauterine environment
Secondary - caused by “external agents” or alterations in other body systems that can compromise the immune system
B: Secondary is more common than Primary (primary is rare)
List 6 predisposing factors for secondary immunodeficiency
- age
- malnutrition
- tumours
- cytotoxic drugs/irradiation (cancer drugs can kill immune cells)
- other diseases incl. diabetes
- infections incl. malaria, HIV
Name 4 common environmental antigens or normal flora that you could have a secondary immunodeficiency to
- candida albicans
- scedosporium species
- fusarium species
- pseudomonas aeruginosa
Diseases related to secondary immunodeficiencies are often due to re-activation of latent infection. Name 6 microorganisms that could achieve this
- pneumocystis carinii
- toxoplasma gondii
- herpes simplex virus (HSV)
- cytomegalovirus (CMV)
- varicella zoster virus (VSV)
- mycobacteria
What 3 ways are hypersensitivities recognised clinically as?
- allergies
- autoimmune disease
- graft rejection
How many types of hypersensitivity classifications are there? Briefly explain them
Type 1: involves inflammatory response to allergens mediated by IgE
Type 2: where you have IgG and IgM antibodies that react with host cell antigens (particularly antigens expressed on host surface)
Type 3: is immune complex mediated
Type 4: is cell-mediated hypersensitivity or “delayed type”
What type of local (3) and systemic (1) responses can you get with type 1 hypersensitivity? Which is more common? local or systemic?
local: (common)
- rhinitis
- bronchoconstriction
- conjunctivitis
systemic; (rare)
- anaphylaxis
Describe the responses to type 1 hypersensitivity [in regards to time and phases]
They have both an immediate and delayed phase
Describe in 2 steps how a type 1 hypersensitivity occurs
- innocuous environmental antigens (e.g. pollens) stimulate the production of IgE antibodies which bind to local mast cells
- allergen becomes bound to mast cell by the IgE antibody on subsequent exposure
What type of cell mediates IgE mediated reactions?
TH2 lymphocytes
Name the 2 phases of a type 1 hypersensitivity reaction
- Sensitization phase
2. Elicitation phases
Describe in 3 steps the sensitization phase of type 1 hypersensitivity reactions
- In the presence of IL-4 and IL-33, the APCs will drive differentiation of T cells into TH2 cells
- TH2 activates the production of basophils
- TH2 also activates B cells to become plasma cells and start secreting IgE antibodies
Describe in 6 steps the elicitation phase of type 1 hypersensitivity reactions [continuing on from sensitization phase]
- IgE binds to mast cells in tissues via high affinity FceR
- Allergens cross-link the IgE on the surface of mast cells in tissues
- The cross link causes mast cell degranulation
- Rapid release of granules containing things like histamine
- 10-30 mins later, leukotrienes and prostaglandins are released from mast cells
- more than 10-30 mins: cytokines (TNFa and IL-4) are released from mast cells to exacerbate the allergic reaction
What does degranulation of the mast cell result in? What is contained within granules? (5)
results in the rapid release of preformed granules that contain: histamine, heparin, tryptase, chymase, TNFalpha
Name 4 typical allergic responses to hypersensitivity reactions. Are types of allergic responses tissue dependent?
- vasodilation
- increased permeability of blood vessels/capillaries in affected area
- smooth muscle contraction
- fluid secretion
Yes they are.
Describe the effects of an allergic response in the GI tract (2). What clinical symptoms can this result in? (2)
- Increased fluid secretion
- Increased peristalsis
Symptoms include:
- diarrhea
- vomiting