Immune System Flashcards
What two intrinsic systems make up the immune system?
Innate and adaptive
Which is antigen specific between innate and adaptive?
Innate
What are the constituents of the innate system?
1st and 2nd line of defense
What is the first line of defense
External body membranes
(Skin and mucosae)
What is the second line of defense?
Antimicrobial proteins, phagocytes inflammation and other cells
What are the constituents of the adaptive defense system?
Third line of defense
What is the third line of defense?
Attacks particular foreign substances
Fun facts about innate and adaptive defenses
Both recognize many of the same defensive molecules
Innate defenses do have specific pathways for certain substances
Innate responses release proteins that alert cells of the adaptive system
Simplified overview of innate and adaptive systems
Innate defense- surface barriers
Skin and mucous
Internal defenses- phagocytes, natural killer cells, inflammation, antimicrobial proteins and fever
Adaptive - humoral immunity (B cells)
Cellular immunity (T cells)
Acid inhibits microbe growth
Enzymes- lysozyme of saliva and respiratory kill microorganisms
Mucin- sticky mucus that lines digesoand respiratory tract and helps trap microorganisms
Defensins- antimicrobial peptides that inhibits microbial growth
Protective chemicals produced by skin and mucous membranes
Second line of defense cells and chemicals
phagocytes
Natural killer cells
Inflammatory response
Antimicrobial proteins (interferons and complement proteins)
Fever
Pattern recognition receptors
Many second line cells have this. It helps them to recognize and bind tightly to structures in microbes disarming them before they do harm
Toll like receptors
Play central role in triggering immune response
Which cell dies fighting?
Neutrophils
Opsonization
The immune system uses antibodies or complement proteins as opsonins that coat pathogens. This helps phagocytosis
Phagocytosis
Phagocyte adheres to pathogen or debris
Phagocytes form pseudopods that eventually engulf the particles forming a phagasome
Lysozyme fuses with the phagocytic vesicle forming a phagolysysome
Toxic compounds and lysosomal enzymes destroy pathogen
Sometimes exocytosis of the vesicle removes indigestible and residual material
Natural killer cells
Kill by inducing apoptosis in cancer and virus infected cells
Secretes hormones that enhance inflammation
Perforins permeate cell membrane to release cell contents
Cardinal signs of acute inflammation
Redness and heat because of dilation of blood vessels
Swelling because of compressed nerves
Pain
Stages of inflammation
Inflammatory chemical release
Vasodilation and increased vascular permeability
Phagocytes mobilize
Inflammatory chemical release
Chemicals are released into ECF by injured tissues or immune cells
Histamine
Released by mast cells. Attracts macrophages
Other inflammatory mediators
Kinins , prostaglandins, cytokines and if pathogens are involved complement
What do these inflammation chemicals have in common?
All cause vasodilation of local arterioles
All make capillaries leaky
Many attract phagocytes to area
What does vasodilation and increased vascular permeability cause?
Vasodilation causes hyperemia and the increase in capillary permeability causes exudate
Hyperemia
Congestion with blood
It leads to redness and heat
Exudate
Fluid containing clotting factors and antibodies leak into tissue. Leads to swelling (edema) and swelling pushes on nerves resulting in pain
Tissue response to injury
Phagocytes mobilize
Four steps
Release of neutrophils from bone marrow in response to leukocytosis -inducing factors from injured cells
Leukocytosis
Endothelial cells of capillaries in inflamed area project cell adhesion molecules (CAMs) into vessel lumen that grab onto passing neutrophils, causing them to slow and roll along, clinging to vessel wall
Margination
Neutrophils flatten and squeeze between endothelial cells, moving into interstitial spaces
Diapedesis
Inflammatory chemicals act as chemotactic agents that promote positive chemotaxis of neutrophils toward the injured area. WBC’s are drawn to area of inflammation
Chemotaxis
Antimicrobial proteins
Interferons and fever + complement proteins
Interferons
Prevents replication of virus when virus enters our body by warning other cells
Complement proteins
Enhance cell lysis , phagocytosis and inflammation
Fever
Prevent microbial proliferation by making essential substances unavailable to them
Adaptive immunity
Responsible for determining which lymphocyte cell or cells will eventually become activated
Systemic
Not restricted to initial site
Memory
Mounts and even stronger attack to known antigens
Humoral immunity
Antibodies produced by lymphocytes circulate freely in body fluids
Extracellular targets
Cellular immunity
Lymphocytes act against target cell
Cellular immunity gas cellular targets
Characteristics of antigens
Can be complete or hapten (incomplete)
Contain anti genetic determinants
Can be self antigen
Present in the external surface of cells
Can be anything that is seen as foreign
What are the antigen presenting cells
Macrophages
Dendritic cells
B cells
Active humoral immunity
Occurs when B cells encounter antigens and produce antibodies against them
What are the two types of active humoral immunity
Naturally acquired and artificially acquired
Active naturally acquired
Formed in response to actual bacterial or viral infection (mumps)
Active artificially acquired
Formed in response to vaccine of dead or attenuated pathogens
Passive humoral immunity
Occurs when ready made antibodies are introduced into body
Passive naturally acquired
Antibodies delivered to fetus via placenta or to infant through milk
Passive artificially acquired
Injection of serum, such as gamma globulins
IgM
First antibody released
Potent agglutinating agent
Readily fixes and activates complement
IgA
Found in mucus and other secretions
Helps prevent entry if pathogens
IgD
Attached to the surface of B cells
Functions as B cells receptors
IgG
75_85% of antibodies in plasma
From secondary to late response
Crosses placental barrier
IgE
Active in some allergies and parasitic infections
Causes mast cells and basophils to release histamine
B lymphocytes (plasma cells) make antibodies
Antibody targets and functions
Antibodies do not destroy antigens ; they inactivate and tag them
Antigens-antibody immune complex
Activates complement proteins
Defensive mechanisms used by antibodies
Neutralization
Agglutination
Precipitation
Complement fixation
