Immunity part 3 Flashcards
What is active immunity?
The specific protection that is acquired through exposure to antigens
This is either achieved by your:
ADAPTIVE IMMUNE RESPONSE (to having caught the disease/ infection etc)
Through IMMUNISATION (aka vaccination) (to that specific disease infection)
The initial exposure to a pathogen can take a few days or weeks to respond to. However, the second time you come across that pathogen, because of memory B cells, your body will remember how to fight off the infection in a few hours.
An acquired immune response can improve on repeated exposures to an injected antigen, or a natural infection
What is passive immunity?
Is immunity transferred from another source
An infant receives passive immunity naturally from the transfer of antibodies from the mother in utero (IgG) and through breast milk (IgG & IgA).
Maternal IgG crosses the placenta in the last few weeks of pregnancy and protects the newborn during the first few months of life.
Therefore, infants born prematurely may be deficient
IgA is transferred to the newborn through breastmilk.
Normally an infant has few infectious diseases during the first few months due to protection provided by the mother’s antibodies.
Passive immunity only provides short term protection that lasts weeks to months.
How do we regulate the immune response?
Normally, after exposure to a pathogen the immune response is activated.
It is usually self limiting because:
the pathogen has been eliminated
Cytokines & antibodies produced by the immune response have a limited life span & are only secreted briefly for antigen recognition.
A second way we regulate the immune response is through Tolerance
What is tolerance?
A term used to define the ability of the immune system to be non-reactive to self-antigens whilst producing immunity to foreign agents.
Tolerance to self antigens protects an individual from harmful autoimmune reactions.
Exposure of an individual to foreign antigens may also leads to tolerance and the inability to respond to potential pathogens that cause infection.
Note – You also get specialized regulation in important organs such as as the brain, testes, ovaries and eyes and so immune damage in these areas can result in serious consequences.
To function properly, the immune system must be able to differentiate foreign antigens from self antigens.
It is the Major Histacompability Complex (MHC) which serve as recognition markers for self and none self
Tell me about Regulation of the Immune Response
Self regulation is an essential property of the immune systems.
An inadequate immune response may lead to IMMUNODEFICIENCY
An Inappropriate of excessive reaction can lead to AUTOIMMUNE DISEASES.
(It involves all aspects of the immune response: Antigen, Antibodies, Cytokines, Regulatory T Cells, & Neuroendocrine system)
What are the Tolerance Mechanisms?
Central Tolerance
Peripheral Tolerance
What is central tolerance?
Eliminate self reactive B-Cells & T- Cells in the central lymphoid organs (Thymus for T- Cells, Bone Marrow for B-Cells)
What is peripheral tolerance?
is the deletion or inactivation of autoreactive T- cells or B-cells that escaped elimination in the central lymphoid organs
Tolerance is moderated by?
T Regulatory cells
What is tolerance and ageing?
As we age, there are changes in immune responsiveness including:
Cell meditated and humeral responses
Elderly people, compared to younger individuals tend to be susceptible to:
infection
have more evidence of autoimmune disorders
Higher prevalence of cancer
Thought may be (in part) due to a biological clock
of T Cell function.
What are disorders of the immune response?
Normally, the immune system is a combination of complex defence mechanisms that work together to protect us.
It works to fight infection, heal damaged tissue and prevent disease.
Occasionally, inadequate or inappropriate activation of the immune system can lead to debilitating or life-threatening illnesses which we define as:
Allergies or Hypersensitivity reaction
Transplant rejection
Autoimmune Disorders
Immunodeficient states
Disorders caused by the immune system are collectively called ?
Hypersensitivity Reactions
What are the 4 types of Hypersensitivity disorders?
Type I - Immediate Hypersensitivity Disorders
Type II- Antibody Mediated Disorders
Type III - Immune Complex Mediated Disorders
Type IV - T- Cell Mediated Disorders
What are Type I, Immediate Hypersensitivity Disorders
Aka Allergic Reactions
IgE Mediated
Begin rapidly (often within minutes of an antigen presentation)
Antigens referred to as allergens
Examples of allergens include:
house dust mites, animal dander, foods, chemicals (e.g. antibiotic penicillin).
Exposure to an allergen can range from:
Mild / annoying e.g. seasonal rhinitis
Moderate & interfering e.g. asthma
Life threatening e.g. anaphylaxis.
What is the physiology behind Type I, Immediate Hypersensitivity Disorders?
An often harmless antigen reacts with a specific IgE antibody located on the membrane receptors on mast cells and blood basophils
This reaction between antigen & antibody causes rapid release of pre formed potent vaso-active and inflammatory mediators- including histamine.
This reaction also causes a rapid production of leukotrienes & prostaglandins which are released into the adjacent tissue.
The effect of all these chemicals (leukotrienes, prostaglandins, histamine) into the tissues cause:
Vasodilation
Smooth muscle Spasm
Increased Permeability of small Blood Vessels
Excessive secretion by epithelial cells
