7c- second line of defence Flashcards
what are phagocytes?
Phagocytes are cells that perform phagocytosis, consuming and destroying foreign or dead material, engulfing it through endocytosis
what are the cellular components of the second line of defense?
all of the cells involved in second line of defence are known as leukocytes or white blood cells
what happens once the dead material is engulfed by phagocytes?
once engulfed, lysosomes within the phagocytes, which contain antimicrobial enzymes called lysozymes, fuse with the vesicles containing the material and destroy it
what is a neutrophil?
most common type of leukocyte in the body. Engages in phagocytosis of pathogens and foreign material, as well as the release of cytokines
what are macrophages and dendritic cells?
a type of leukocyte that engages in phagocytosis and antigen presentation, also known as antigen presenting cells (APC’s). They consume and destroy foreign material as well as present antigens from the consumed material on their surface.
what do macrophages and dendritic cells stimulate?
stimulate specific immune response
what are antigen presenting cells?
APC’s are specific cells that express MHC class II to display consumed antigens on their surface, enabling interaction with the adaptive immune system.
how do phagocytes communicate within the immune system?
phagocytes release a number of substances such as cytokines, which are important cell signalling molecules which help protect against pathogens and help guide immune cells to the site of infection or injury, allowing them to function optimally.
what are cytokines?
cell signalling molecules which help protect against pathogens and help guide immune cells to the site of infection or injury, allowing them to function optimally.
what are natural killer cells?
Natural killer cells are a type of leukocyte responsible for the recognition and destruction of damaged and/or infected host cells.
How do natural killer cells achieve their job?
They achieve it with the help of 2 receptors called killer inhibitory receptor and killer activation receptor
what is the killer inhibitory receptor?
examines surface of cells for MHC class I markers
what is the killer activation receptor?
binds to certain molecules which appear on cells undergoing cellular stress
how can presence of MHC class I markers be altered?
due to various disease processes. Viral infections either destroy or suppress production of MHC Class I markers, leading to their absence
when is cell death initiated?
Cell death is initiated only in infected or abnormal cells that lack a sufficient MHC Class I markers.
what is the role of the two receptors in the scenario of cell death?
The killer inhibitory receptor is unable to bind to enough MHC class I markers as the presumed cell about to undergo cell death lacks a sufficient number of MHC Class I markers and thus the killer inhibitory receptor is unable to inhibit the cell death signal. This activates the killer activation receptor, initiating cell death.
when does cell death NOT occur?
if killer inhibitory receptor detects a sufficient number of MHC Class I markers, it overrides the killer activation signal, preventing cell death.
where do mast cells reside, and what is the role of mast cells?
Mast cells reside in connective tissues throughout the body. Their role is to become activated and degranulate to release histamine when they detect injury to surrounding cells or are stimulated by antigens or allergens.
What is the effect of histamine on the body?
Histamine has several effects on the body and plays a crucial role in the inflammatory response
what are eosinophils?
Eosinophils are large granulated cells containing various toxic chemical mediators such as DNases, RNases and proteases, which help destroy invading pathogens.
