Immune System Part III: Adaptive Immune System & Cell Mediated Immunity.
Immune System
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Immune System
• Innate immunity is present before any exposure to pathogens and is effective from the time of birth
• It involves nonspecific responses to pathogens• Innate immunity consists of external barriers plus
internal cellular and chemical defenses• Key internal defenses are macrophages and other
phagocytic cells
• Acquired immunity, or adaptive immunity, develops after exposure to agents such as microbes, toxins, or other foreign substances
• It involves a very specific response to pathogens• Recognition is by white blood cells called lymphocytes• Some lymphocytes produce antibodies; others destroy
infected cells, cancer cells, or foreign tissue
LE 43-2
Invadingmicrobes
(pathogens)
External defenses
SkinMucous membranesSecretions
INNATE IMMUNITYRapid responses to a
broad range of microbes
ACQUIRED IMMUNITYSlower responses to
specific microbes
Internal defenses
Phagocytic cells
Inflammatory response
Humoral response(antibodies)Antimicrobial proteins
Natural killer cells Cell-mediated response(cytotoxiclymphocytes)
LE 43-4
PseudopodiaMicrobes
MACROPHAGE
Lysosomecontainingenzymes
Vacuole
Natural Killer Cells
• Natural killer (NK), also known as Cytotoxic T Cells, cells attack virus-infected body cells and cancer cells
• They trigger apoptosis in the cells they attack
LE 43-14_3
First exposure to antigen
Antigens engulfed anddisplayed by dendritic cells
Activate
Humoral immune response Cell-mediated immune response
HelperT cell
Active andmemoryhelperT cells
Gives rise to
Antigens displayedby infected cells
Activate
CytotoxicT cell
Memorycytotoxic
T cells
Gives rise to
Secretedcytokinesactivate
Activecytotoxic
T cells
Defend against infected cells, cancercells, and transplanted tissues
Activate
Gives rise to
Secrete antibodies that defend againstpathogens and toxins in extracellular fluid
Plasmacells
MemoryB cells
B cells
Intact antigens