What is immunity? Flashcards
What is the definition of Immunity?
It is the aBILITY OF AN ORGANISM TO RESIST A PARTICULAR INFECTION OR TOXIN BY THE ACTION OF SPECIALISED CELLS.
What is active and passive immunity?
They are both subunits of the acquired arm.
Active - you can feel it e.g. you have a cold and you feel rough because that’s your body fighting it off. It can be natural (from a natural infection) or artificial (vaccines).
Passive - you cant feel it its just happening. It can be natural (what’s passed to you from your mother through the placenta - placental transfer of IgG) or artificial (the human IgG).
How do the innate and acquired arms of the immune system communicate with one another?
Dendritic cells and macrophages (APCs).
What is a brief summary of the phases of immune response?
Starts with the innate - inflammation, complement activation, phagocytosis and destruction of the pathogens.
Moves to the adaptive - interaction between APCs and antigen specific T cells, recognition of the antigen and T-cell proliferation; activation of antigen specific B cells, formation of effector and memory T cells, interaction of T and B cells, formation of effector and memory B cells and production of the antibody.
Immunological memory - maintenance of memory B and T cells, and high serum or mucosal antibody levels to protect against reinfection.
What is the goal of the immune system?
- clear potential pathogens in a controlled and efficient process
- limit pathology in the host
- appropriate duration - returning to homeostasis asap
- not attack the self
- remove non-healthy cells e.g. tumours
- confer future protection
What is a brief history of immunity discovery?
1796 Edward Jenner - smallpox work and creation of the vaccine (‘vacca’ means cow).
Late 19th century:
- Robert Koch + Lois Pasteur = germ theory of disease
- Louis Pasteur = vaccination with attenuated organisms for chicken cholera and rabies.
- Elie Metchnikoff = identification oof phagocytes (immune cells eating pathogens)
- Paul Ehrlich - proteins in blood conveying protection from pathogens by reacting with components of pathogens termed antigens (Ag).
What type of immunity has James Phipps acquired after Edward Jenner infected him with cowpox?
Active artificial immunity - through a vaccine.
What is artificial immunity - Vaccines?
Vaccines inject substances used to stimulate production of antibodies and provide immunity against one of several diseases. They’re prepared from the causative agent of disease, its products of a synthetic substance that is treated to act as an antigen, but without inducing the disease.
What is herd immunity?
Immunisation can protect an individual and the population as the disease will decline with everyone being immune to it.
E.G.
Measles - over 95% of population need to be immune to prevent outbreaks, MMR vaccine introduced in 1988.
What are the four types of vaccine?
Live (attenuated) - live organism such as small pox, MMR, yellow fever
Killed (inactive or attenuated)
Subunit - proteins from pathogen cell wall e.g. meningitis vaccine
Nucleic acid - mRNA vaccines e.g. covid.
What is humoral or cellular immunity?
Humoral (antibody mediated immunity) - adaptive immunity that produces antigen specific antibodies to destroy the antigens.
Activated B-lymphocytes. Destroys extracellular pathogens.
Cellular (cell mediated immunity) - adaptive immunity producing antigen specific T-cells to destroy antigens. Activates T-lymphocytes. Destroys intracellular pathogens.
What are antibodies?
They are produced by plasma cells (mature B lymphocyte cells).
B cells have B cell receptors on their surface, they are similar to antibodies. When the B-cell recognises the antigen, the B-cell receptor will bind to the antigen, and the B-cell will then produce a lot of specific antibodies against the antigen.
Where are all immune cells derived from?
A cell in the bone marrow (haematopoietic stem cell).
What is clonal selection for development of adaptive immune response?
A single progenitor (ancestor) cell gives rise to a large number of lymphocytes, each with different specificity.
Each B cell will have an individual target antigen, we need to remove all B cells with receptors that target our own cells.
You’re then left with naïve lymphocytes (B-cells) that have unique B-cell receptors targeting foreign antigens. When an antigen binds to the specific B-cell, the body knows it needs more of these specific B cells and will rapidly proliferate them.
What are the primary lymphoid tissues?
Bone marrow - soft spongy tissue filling the internal cavity of bones.
Thymus - specialised gland.
