Pathophysiology of Allergy Flashcards
What are some examples of allergic diseases?
Allergic diseases include asthma, dermatitis, conjunctivitis, rhinitis, and allergies to food, drugs, or insects. Anaphylaxis is a severe form of an allergic reaction.
What is atopic diathesis?
Atopic diathesis refers to a genetic predisposition that makes individuals more susceptible to immediate hypersensitivity reactions, also known as allergic diseases.
What types of cells are involved in allergic inflammation?
Allergic inflammation involves resident cells such as epithelial cells, dendritic cells, macrophages, smooth muscle, fibroblasts, endothelial cells, and nerves, as well as infiltrating cells like mast cells, eosinophils, T-lymphocytes, B-lymphocytes, neutrophils, and innate lymphoid cells.
How do mediators contribute to allergic inflammation?
Mediators released by resident and infiltrating cells play a key role in initiating allergic sensitization. These mediators, such as histamine and cytokines, can affect smooth muscle contraction, vascular permeability, and the recruitment of other inflammatory cells.
What are some common allergens?
Common allergens include house dust mites, fungi, domestic pets, and exposure to occupational chemicals.
How does allergic sensitization begin?
Allergic sensitization begins when antigen-presenting cells (APCs) detect an allergen and present it to T-lymphocytes. The mediator environment influences the development of a Th2 response, which leads to allergen-specific IgE production by B-lymphocytes.
What role do IgE, mast cells, and basophils play in allergic reactions?
IgE is the key immunoglobulin in immediate hypersensitivity. It binds to mast cells and basophils, “sensitizing” them to allergens. Upon re-exposure to the allergen, these cells release mediators like histamine, which trigger allergic reactions.
What is the role of eosinophils in allergic reactions?
Eosinophils are key players in allergic reactions and may be elevated in blood counts during allergy. They contain granules with proteins, enzymes, and reactive oxygen species, which are released upon cell activation.
How do epithelial cells contribute to allergic reactions?
Epithelial cells protect mucosal surfaces like the skin and airways. They interact with allergens, especially enzymes from allergens like house dust mites, which activate the cells through protease-dependent mechanisms, triggering allergic responses.
What is “biological redundancy” in the context of allergic inflammation?
Biological redundancy refers to the phenomenon where the effects of a single inflammatory marker can be duplicated by other mediators, which has important implications for drug treatments targeting inflammatory pathways.
What cells are responsible for initiating allergic inflammation in tissues?
Resident cells in tissues, such as epithelial cells, dendritic cells, and macrophages, are responsible for initiating allergic inflammation. These cells interact with infiltrating immune cells like mast cells and eosinophils.
What is the role of cytokines and chemokines in allergic responses?
Cytokines and chemokines are newly generated mediators that contribute to allergic responses. They play roles in the recruitment of inflammatory cells, the promotion of tissue remodelling, and the overall regulation of the allergic response.
How do reactive oxygen and nitrogen species contribute to allergic inflammation?
Reactive oxygen and nitrogen species are produced during allergic inflammation and play a significant role in damaging tissues, amplifying the immune response, and promoting further allergic sensitization.
What does IgE bind to on mast cells and basophils?
IgE binds to high-affinity IgE receptors (FcεRI) on mast cells and basophils. This binding “sensitizes” the cells, making them primed for activation upon re-exposure to the same allergen.
How do mast cells and basophils contribute to allergic responses?
Mast cells and basophils release a variety of mediators, including histamine, when activated by allergen-specific IgE. These mediators contribute to symptoms of allergic reactions such as swelling, redness, and smooth muscle contraction.
What is the role of T-lymphocytes in allergic sensitization?
T-lymphocytes, particularly Th2 cells, are crucial in allergic sensitization. They help promote the production of allergen-specific IgE by B-lymphocytes, leading to the development of allergic responses.
Why are eosinophils considered a hallmark cell of allergy?
Eosinophils are considered a hallmark cell of allergy because they are commonly elevated during allergic reactions. They contain granules with proteins and enzymes that, when released, exacerbate inflammation and contribute to tissue damage.
How does allergen exposure lead to the activation of smooth muscle in the airways?
Allergens cause the release of mediators like histamine, which act on smooth muscle in the airways, leading to contraction. This results in the narrowing of airways, which is a characteristic symptom of conditions like asthma.
What is the significance of “vascular leakiness” in allergic inflammation?
Vascular leakiness refers to the increased permeability of post-capillary venules, allowing plasma to exude into the surrounding tissues. This contributes to swelling (edema) and the recruitment of other inflammatory cells, amplifying the allergic response.
What is the process of an allergen being identified and its response?
- Allergen penetrates through the skin
- The allergen is detected by the antigen presenting cells.
- The MHC2 binding the APCs.
- This leads to the T helper cells to produce a B lymphocyte.
- The B lymphocytes lead to IgE being produced.
- The IgE binds to the IgE receptors on the mast cells.
- This leads to mast cell degranulation.
- This leads to histamine getting released from the mast cells.
- This histamine binds onto the H1 receptors (in nerves, respiratory epithelium, endothelial cells, hepatic cells, vascular smooth muscle cells, dendritic cells and lymphocytes) leading to the allergic reaction.
