Chapter 16 Terms (Autoimmunity) Flashcards
Autoimmunity
The failure of mechanisms of the immune system to inactivate or eliminate self-reactive cells.
Self-Tolerance
Results from the delibrate inactivation or destruction of lymphocytes bearing BCRs or TCRs that recognize & bind self-epitopes.
Central Tolerance
- Occurs during early differentiation of B cells in the bone marrow & t ceclls in the thymus.
- Mechanism by which newly developing T & B cells are rendered non-reactive to self.
Peripheral Tolerance
- Several mechanisms that control or eliminate autoreactive B & T cells after they exit the bone marrow or thymus.
- Includes Anergy & Suppression
Anergy
- A state of nonresponsiveness in lymphocytes after their receptors bind antigen (B cell) or pMHC (Tcell).
- Receipt of the first signal in the absence of second signal causes naÏve T cells to enter anergy.
- CD8+ & B Cells
Suppression
- Regulatory cells (Usually T cells) inhibit the activity of other cells.
- CD4+CD25+ T cells diminish activity of T cells stimultaed by various epitopes
Th1 Cells
- The host immunity effector against intracellular bacteria & protozoa.
- Triggered by IL-12 & IL-2
- Effector cytokine is IFN-gamma
- Main effector cells are mcrophages, CD8 T cells, IgG B cells, & IFM-gamma CD4 T cells
Th2 Cells
- Host immunity effectors against extracellular parasites including helminths
- Triggered by IL-4
- Their effector cytokines are IL-4, IL-5, IL-9, IL-10, & IL-13
- Main effector cells are eosinophils, basophils, mast cells, B cells, & IL-4/IL-5 CD4 T cells
Autoimmune Inflammatory Bowel Disease
- May be due to changes that favor developement of Th1-like cell-mediated inflammatory responses, perhaps triggered by pathogenic bacteria.
- Includes: Crohn’s Disease & Ulcerative Colitis
Molecular Mimicry
A process in which infection by particular microbes is associated with the subsequent development of specific autoimmune diseases.
Reactive Arthritis
- A group of inflammatory arthritis diseases that occur more frequently in individuals who have had food poisoning.
- Includes Ankylosing Spondylitis & Reiter Disease
Ankylosing Spondylitis
- Usually involving the lower spine
- Chronic inflammatory disease of the axial skeleton.
Reiter Disease
Affecting the joints of the lower limbs & the gastrointestinal/genital/urinary tracts.
Myasthenia gravis
- Neuromuscular disease that leads to fluctuating muscle weakness & fatigue.
- In most common cases, muscular weakness is caused by circulating antibodies that block acetylcholine receptors.
- Localized
Epitope Spreading (ES)
Development of an immune response to epitopes distinct from, & noncrossreaction with, the disease-causing epitope.
Immunologically Privileged Sites
Sites in the body that are associated with some degree of isolatio from the immune system
Blood-Brain Barrier
Consists of dense, tightly packed vascular endothelium that limits the flow of cells & large molecules from the vasculature into the brain, thus decreasing the ability of the immune system to infiltrate the brain.
Cryptic Epitope
If the molecule is altered by denaturation or cleavage, the “hidden” internal epitopes may become exposed & available for recognition & binding by antibodies.
Rheumatoid Factors
IgM antibodies directed at the cryptic carbohydrate structures on antigen-bound IgG molecules.
Neoantigens
Self-antigens that have been modified by some extrinsic factor so that they appear foreign to the immune system.
Cell-Mediated Autoimmune Diseases
- Insulin-Dependent Diabetes Mellitus (type 1)
- Multiple Sclerosis
- Reactive Arthritis
- Rheumatoid Arthritis
HLA Association with Autoimmune Disease
The risks for many autoimmune diseases appear to be associated with the presence of particular HLA genes.
Relative Risk
Compares frequency of particular disease among carriers of a particular HLA gene witht he frequency among non-carriers.
