hypersensitivity Flashcards
what is hypersensitivity more commonly known as?
Allergy / autoimmunity Hypersensitivity is a growing problem
what is happening to the incidence of children with asthma in the population?
There is a large increase in children suffering from asthma.
what is happening to the amount of allergic diseases among adults in the population?
large increase in allergic diseases among adults
How is hypersensitivity a growing problem in the dental surgery in terms of the dental team?
Dentists and nurses are becoming increasingly sensitised to latex and dental materials.
How is hypersensitivity a growing problem in the dental surgery in terms of patients?
Patients are becoming increasingly sensitised to latex, dental materials and drugs used in the surgery
what are the 2 components of the immune system?
innate immune system and acquired immune system
what does acquired immunity consist of? (2)
Antibody response (humoral response) Cell mediated response BOTH are involved in hypersensitivity reactions.
How is MHC II involved in antigen presentation?
B cells present antigens to T Cells via MHC II.
- mIgM (or mIgD) binds to the antigen (Ag)
- phagocytosis occurs
- a peptide is displayed on the surface with MHC II (these are molecules found on antigen-presenting cells)
- TCR (T cell receptor) of naive T helper cells (CD4) binds to MHC II
- lots of other co-stimulatory molecules are required.
How do T cells help B cells? Think about how they cause clonal expansion
APC eats Ag (extrinsic) and presents it to naïve CD4+ T cells (via MHC II)
These turn into Th2 cells
Th2 cells bind to B cells that are presenting Ag (via MHC II). This Ag has been captured using the mIgR on cell surface.
Th2 cell now secretes cytokines (IL-4, IL-5, IL-10 and IL-13 )
These cause B cells to divide – CLONAL EXPANSION and differentiate into Plasma cells (AFC = antibody forming cell) and Memory B cells (Bm)
What are the stages of the antibody response to a pathogen?
- antigen uptake by cell
- antigen processing
- antigen presentation by an APC
- B cell binds to APC
- T cell help (involves cytokines)
- B cells proliferate to form plasma cells.
- Antibody is produced
How long does the antibody response take? Why is the antibody response often systemic/widespread?
It occurs quickly
This is because antibodies are soluble proteins that can reach most parts of the body quickly via:
Blood
Tissue fluids
Body secretions
Explain the stages of cell mediated immunity for both first and second exposures to the antigen?
1st exposure to antigen:
- Antigen uptake
- Antigen processing
- Antigen presentation in the context of MHC
- T cell receptor on the naive T cell binds to MHC on the antigen presenting cell.
- T cell then becomes activated
- This activated T cell proliferates to form many antigen specific memory T cells that patrol the body.
2nd exposure to antigen:
- T cell recognises the antigen expressed on the target cell in the context of MHC.
- The T cell can then respond by releasing cytokines / killing the target cell by apoptosis
![](https://s3.amazonaws.com/brainscape-prod/system/cm/315/441/516/a_image_thumb.png?1593866112)
How does Th1 (CD4) activation occur?
APC presents Ag with MHC II to naïve CD4 cell
Stimulation with high levels of IL-12 activate naïve cells to Th1 cells
Th1 cells go to secondary lymphoid tissue (spleen, lymph nodes)
Activated Th1 (CD4) cells proliferate (clonal expansion)
Th1 cell recognises Ag on infected cells (with MHC II) via TCR (CD4) Th1 secretes INFγ – stop virus spread (apoptosis)
![](https://s3.amazonaws.com/brainscape-prod/system/cm/315/441/783/a_image_thumb.png?1593866270)
What is cell mediated immunity directly mainly against? Are cellular immune responses fast or slow?
Cellular targets such as tumour cells, virally transformed cells and foreign cells.
Cellular immune responses tend to be localised, slow to develop and slow to resolve.
What if the immune system fails to produce an adequate immune response?
Immunodeficiency
what if the immune system produces an overactive, damaging response?
Hypersensitivity - allergy
What is hypersensitivity?
When the immune system responds in an exaggerated or inappropriate way resulting in harm.
Usually occurs on second or subsequent exposure to the antigen
Hypersensitivity is a characteristic of the individual (genetic susceptibility)
What are the 4 types of hypersensitivity?
Which are antibody-mediated and which are cell-mediated?
Type I - Immediate/anaphylaxis
Type II - Cytotoxic
Type III - Immune complex
Type IV - Delayed
Type I, II, III are antibody-mediated, type IV is cell-mediated.