Download Innate and adaptive immunity

INTRODUCTION TO THE
IMMUNE SYSTEM
Innate and adaptive immunity
The course of a typical antibody response:
The adaptive response takes 7-14 days to develop and
mount a specific, protective immune response
An infection, and the response to it can be divided into
stages and involves soluble mediators and cells of the
immune system
The adaptive immune response develops
in the lymphoid tissues
Sentinel cells
in the
periphery
pick up
pathogens and
transport them
to the draining
lymph node
Circulating
lymphocytes
encounter
antigen in
peripheral
lymph nodes
The immune response is dynamic, involving cells recirculating from the tissues via the lymphatics and blood
system
•Innate immunity acts locally in the infected tissue,
•Adaptive immune responses develop in the lymphoid
tissues,
•Effector cells multiply and migrate back to tissue.
Cellular components of the immune system
Myeloid cells in innate and adaptive immunity
Phagocytic cells
Blood monocytes
Polymorphonuclear
neutrophils
Phagocytosis
The mononuclear phagocyte system
Mobilisation of defensive components of
innate immunity
Macrophages and acute inflammation
Lymphocytes mediate adaptive (pathogen specific)
immunity: each cell has a unique antigen receptor
B cells need T cell “help” to make antibody
Innate and adaptive (acquired) immunity are
integrated
SUMMARY
The response to an initial infection occurs in three
phases: innate, early induced, adaptive.
Cells of the innate immune system:,
macrophages, granulocytes, natural killer cells,
immature B cells
• Release of soluble components to opsinise
phagocytosis
• Release of toxic granules to kill micro-organisms,
parasites or virally infected cells
• Release of soluble mediators to attract other
leukocytes to site of inflammation
• Removal of dead or dying cells
• Transfer of infectious or toxic material to lymph nodes
to initiate adaptive immune response
Cells of the adaptive immune system:
Dendritic cells, T and B lymphocytes,
• Lymphocytes are generated with unique antigen
receptors on their surface.
• Dendritic cells (and macrophages) present antigen to
lymphocytes and provide activating signals
• Lymphocytes undergo clonal expansion and migrate
back to area of infection as effector cells.
• T cytotoxic cells selectively kill virally infected cells
• T helper cells selectively help B cells produce large
amounts of high affinity specific antibody.
• After infection, memory lymphocytes provide
protective immunity
Natural killer cells kill virally infected cells
Virally induced
structures
IFN-g released by infected cell “primes”other cells to kill it