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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 - PowerPoint PPT Presentation
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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