Chapter 8: The Immune System Flashcards
Structure of the Immune System
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The immune system can be divided into
- innate
- adaptive immunity
Innate immunity is composed of
defenses that are always active, but that cannot target a specific invader and cannot maintain immunologic memory; also called nonspecific immunity.
____ is composed of defenses that are always active, but that cannot target a specific invader and cannot maintain immunologic memory; also called _____.
**Innate immunity
nonspecific immunity**
Adaptive immunity is composed of
defenses that take time to activate, but that target a specific invader and can maintain immunologic memory; also called specific immunity.
____ is composed of defenses that take time to activate, but that target a specific invader and can maintain immunologic memory; also called ____.
Adaptive immunity
specific immunity
The immune system is dispersed in the body.
- Immune cells come from the bone marrow.
- The spleen and lymph nodes are sites where immune responses can be mounted, and in which B-cells are activated.
- The t_hymus_ is the site of T-cell maturation.
- Gut-associated lymphoid tissue (GALT) includes the tonsils and adenoids.
____, or white blood cells, are involved in ____.
Leukocytes
immune defenses
Leukocytes aka what?
white blood cells
The Innate Immune System
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Many of the nonspecific defenses are
noncellular
- The skin acts as a physical barrier and secretes antimicrobial compounds, like defensins.
- Mucus on mucous membranes traps pathogens; in the respiratory system, the mucus is propelled upward by cilia and can be swallowed or expelled.
- Tears and saliva contain lysozyme, an antibacterial compound.
- The stomach produces acid, killing most pathogens. Colonization of the gut helps prevent overgrowth by pathogenic bacteria through competition.
- The complement system can punch holes in the cell walls of bacteria, making them osmotically unstable.
- Interferons are given off by virally infected cells and help prevent viral replication and dispersion to nearby cells.
The skin acts as a
physical barrier and secretes antimicrobial compounds, like defensins.
Mucus on mucous membranes traps
pathogens; in the respiratory system, the mucus is propelled upward by cilia and can be swallowed or expelled.
Tears and saliva contain
lysozyme, an antibacterial compound.
The stomach produces acid doing what?
The stomach produces acid, killing most pathogens. Colonization of the gut helps prevent overgrowth by pathogenic bacteria through competition.
The complement system can
The complement system can punch holes in the cell walls of bacteria, making them osmotically unstable.
Interferons are given off by
virally infected cells and help prevent viral replication and dispersion to nearby cells.
Many of the nonspecific defenses are also
cellular
- Macrophages ingest pathogens and present them on major histocompati-bility complex (MHC) molecules. They also secrete cytokines.
- MHC class I (MHC-I) is present in all nucleated cells and displays endogenous antigen (proteins from within the cell) to cytotoxic T-cells (CD8+ cells).
- MHC class II (MHC-II) is present in professional antigen-presenting cells (macrophages, dendritic cells, some B-cells, and certain activated epithelial cells) and displays exogenous antigen (proteins from outside the cell) to helper T-cells (CD4+ cells).
Macrophages do what ?
Macrophages ingest pathogens and present them on major histocompati-bility complex (MHC) molecules. They also secrete cytokines.
MHC class I (MHC-I) is present in all
nucleated cells and displays endogenous antigen (proteins from within the cell) to cytotoxic T-cells (CD8+ cells).
MHC class II (MHC-II) is present in
professional antigen-presenting cells (macrophages, dendritic cells, some B-cells, and certain activated epithelial cells) and displays exogenous antigen (proteins from outside the cell) to helper T-cells (CD4+ cells).
Dendritic cells are
antigen-presenting cells in the skin.
Natural killer cells attack
Natural killer cells attack cells not presenting MHC molecules, including virally infected cells and cancer cells.
Granulocytes include
Granulocytes include neutrophils, eosinophils, and basophils.
esosino
baso
neutro
Neutrophils ingest
bacteria, particularly opsonized bacteria (those marked with antibodies). They can follow bacteria using chemotaxis.
Immunization is a method of inducing
active immunity (activation of B-cells that produce antibodies to an antigen) prior to exposure to a particular pathogen.
*there is active immunity and passive immunity
Passive immunity is the transfer of
antibodies to an individual.
*there is active immunity and passive immunity
The Lymphatic System
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The immune system and the lymphatic system are intimately related.
Structure:
The lymphatic system, along with the cardiovascular system, is a type of circulatory system. It is made up of one-way vessels that become larger as they move toward the center of the body. These vessels carry lymphatic fluid (lymph) and most join to form a large thoracic duct in the posterior chest, which then delivers the fluid into the left subclavian vein (near the heart).
Lymph nodes are small, bean-shaped structures along the lymphatic vessels. Lymph nodes contain a lymphatic channel, as well as an artery and a vein. The lymph nodes provide a space for the cells of the immune system to be exposed to possible pathogens.
Function:
The lymphatic system serves many different purposes for the body by providing a secondary system for circulation.
Equalization of Fluid Distribution:
At the capillaries, fluid leaves the bloodstream and goes into the tissues. The quantity of fluid that leaves the tissues at the arterial end of the capillary bed depends on both hydrostatic and oncotic pressures (Starling forces). Remember that the oncotic pressure of the blood draws water back into the vessel at the venule end, once hydrostatic pressure has decreased. Because the net pressure drawing fluid in at the venule end is slightly less than the net pressure pushing fluid out at the arterial end, a small amount of fluid remains in the tissues. Lymphatic vessels drain these tissues and subsequently return the fluid to the bloodstream.
The lymphatics offer some protection against pathology. For example, if the blood has a low concentration of albumin (a key plasma protein), the oncotic pressure of the blood is decreased, and less water is driven back into the bloodstream at the venule end. Thus, this fluid will collect in the tissues. Provided that the lymphatic channels are not blocked, much of this fluid may eventually return to the blood-stream via the lymphatics. Only when the lymphatics are overwhelmed does edema occur—swelling due to fluid collecting in tissue.
Transportation of Biomolecules:
The lymphatic system also transports fats from the digestive system into the blood-stream. Lacteals, small lymphatic vessels, are located at the center of each villus in the small intestine. Fats, packaged into chylomicrons by intestinal mucosal cells, enter the lacteal for transport. Lymphatic fluid carrying many chylomicrons takes on a milky white appearance and is called chyle.
Immunity:
As stated previously in this chapter, lymph nodes are a place for antigen-presenting cells and lymphocytes to interact. B-cells proliferate and mature in the lymph nodes in collections called germinal centers.
- Compare and contrast B-and T-cells:
CHART:
- Both B-cells and T-cells develop in the bone marrow
- B-cells mature in :bone marrow (but are activated in spleen or lymph bodes)
T-cells mature in: Thymus
- B-cells major function: produce antibodies
T-cells major fuction: Coordinate immune system and directly kill infectted cells
- B-cells and T-cells: are both specific (NOT non-specific)
- B-cell: Humoral
T-cell: Cell-mediated
