BM1022 Immune System Flashcards
Natural barriers
Natural barrier to infectious diseases
Intact skin
Normal flora in the gastrointestinal tract
And upper respiratory tract as well as on the skin can compete with pathogens and afford some protection
Leukocytes
White blood cells
Originate in bone marrow (can develop and mature there)
Where do leukocytes travel?
Originate in one narrow and many develop and mature there
Then migrate to peripheral tissues where some reside
Others circulate in the bloodstream and in the lymphatic system, which drains extracellular fluid and delivers them back into the blood
Examples of cells of the immune system (leukocytes)
Neutrophils (PMNs) Eosinophils Mast cells Monocytes Macrophages Dendritic cells Natural killer cells T lymphocytes (=T cells) B lymphocytes (=B cells) Plasma cells
Cytokines
Cytokines are a group of chemical substances that act as messengers within the immune system and between the immune system and other systems of the body
I.e. Cytokines are the language of the immune response
They are protein molecules that are secreted by a range of cells and allow each of these cells to communicate with each other
Cytokines such as interleukin 2 (IL-2) are important as they…
Stimulate the growth of lymphocytes
The group of cytokines known as chemokines are important as they…
Control the movement of cells throughout the body
The cytokines known as the interferons are important for…
Activating macrophages and natural killer cells
Innate immunity
Is non-specific and includes natural, mechanical, chemical and biological barriers to infection
Innate immunity is an extremely active process based around a set of receptors found on cells such as neutrophils and macrophages
These receptors recognise patterns such as sugars in the surface of bacteria as well as components of complement and antibodies that have starch to their respective antigens
Components of innate immunity
Innate immunity consists of cellular and non-cellular defences
Cellular defences include cells like phagocytes and natural killer cells (NK).
Other defences include inflammation and complement
Phagocytes and phagocytosis
Phagocytosis is a process whereby cells such as granulocytes and macrophages will destroy foreign antigens.
WATCH VID
Natural killer cells (NK)
NK’s are part of the innate lymphoid cells and are capable of destroying a variety of targets such as tumour cells, infected cells and damaged cells. VIA a complex system of receptor cells, they identify changes in the surface of abnormal cells. They insert protein molecules, called perforins, into the cells’ membrane, which creates a pore, allowing the NKs to insert toxic substances into the cells and thereby killing them
Inflammation
Inflammation can be acute or chronic. The acute inflammatory response is a non-specific response to tissue injury (e.g. Physical damage, burns, chemical damage or infection)
The major function of inflammation is to clear the injured site of cellular debris and foreign material such as pathogens, thereby repairing the site for the healing process
The four main signs of inflammation are
Redness
Heat
Swelling
Pain
Complement
The complement system is a group of plasma proteins that are present in the blood in an inactive state
When activated, for example by infection, the complement proteins enhance the inflammatory response and can destroy foreign cells (e.g) bacteria and viruses
