4.0 - Immune regulation
Immune Regulation: Maintaining Ba
lance in the Body's Defense System
Introduction
The immune system is a complex network of cells and organs that pro
tects the body from pathogens and other harmful substances. A key f
eature of the immune system is its ability to distinguish between "self"
and "non-self" antigens. This ability is crucial for preventing autoimmu
ne diseases, where the immune system mistakenly attacks the body's
own tissues.
Central Tolerance: The Foundation of Immun
e Self-Recognition
Central tolerance is established during the development of immune
cells in the thymus (for T cells) and bone marrow (for B cells). This pr
ocess ensures that only immune cells that recognize and tolerate sel
f-antigens are allowed to mature and circulate in the body.
T cell selection in the thymus is a critical step in central tolerance. I
mmature T cells undergo a rigorous selection process, where they ar
e tested for their ability to recognize self-antigens presented by thy
mic epithelial cells.
Positive selection: T cells that can recognize self-antigens weakly
are allowed to survive and mature.
Negative selection: T cells that recognize self-antigens strongly ar
e eliminated to prevent autoimmunity.
Incomplete process: Central tolerance is not always perfect, and so
me autoreactive T cells may escape this selection process. This can l
ead to the development of autoimmune diseases.
Peripheral Tolerance: Maintaining Immune H
omeostasis
https://www.studyfetch.com/platform/studyset/6748730d72bff04b73915866/material/67864b89e9fc3843c44dcfe5/document 20/1/25, 14:41
Page 1 of 4
, Peripheral tolerance refers to mechanisms that operate outside the
thymus and bone marrow to prevent autoimmunity. These mechanis
ms are essential for maintaining immune homeostasis and preventi
ng the activation of autoreactive immune cells.
Immunologically privileged sites: Certain tissues, such as the brain,
anterior chamber of the eye, testis, and uterus, are considered immu
nologically privileged. These sites are protected from immune attack
by various mechanisms, including:
Lack of lymphatic drainage: This prevents the migration of immun
e cells to these sites.
Presence of physical barriers: These barriers, such as the blood-br
ain barrier, restrict the entry of immune cells.
Secretion of immunosuppressive factors: These factors suppress t
he activity of immune cells.
Immunologic ignorance: This refers to the sequestration of self-anti
gens by autoreactive clones, preventing their recognition by the imm
une system.
Anatomical Barriers: The Blood-Brain Barrier
(BBB)
The BBB is a highly selective barrier that protects the central nervous
system (CNS) from harmful substances. Only specific molecular sub
stances can pass through the BBB.
Break of anatomical barriers triggers autoimmunity: In multiple scl
erosis, the BBB is disrupted, allowing immune cells to infiltrate the CN
S and attack myelin, leading to neurological damage.
Fas-FasL Interactions: A Crucial Checkpoint f
or Immune Cell Survival
Fas (CD95) and FasL (CD95L) are proteins involved in apoptosis, a pr
ogrammed cell death process.
Mutations in Fas/FasL genes lead to autoimmunity: Mice with mutat
ions in the Fas or FasL genes develop autoimmune diseases, such as
systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), Sjögr
en's syndrome (SS), and autoimmune lymphoproliferative syndrome
(ALPS).
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Page 2 of 4
Immune Regulation: Maintaining Ba
lance in the Body's Defense System
Introduction
The immune system is a complex network of cells and organs that pro
tects the body from pathogens and other harmful substances. A key f
eature of the immune system is its ability to distinguish between "self"
and "non-self" antigens. This ability is crucial for preventing autoimmu
ne diseases, where the immune system mistakenly attacks the body's
own tissues.
Central Tolerance: The Foundation of Immun
e Self-Recognition
Central tolerance is established during the development of immune
cells in the thymus (for T cells) and bone marrow (for B cells). This pr
ocess ensures that only immune cells that recognize and tolerate sel
f-antigens are allowed to mature and circulate in the body.
T cell selection in the thymus is a critical step in central tolerance. I
mmature T cells undergo a rigorous selection process, where they ar
e tested for their ability to recognize self-antigens presented by thy
mic epithelial cells.
Positive selection: T cells that can recognize self-antigens weakly
are allowed to survive and mature.
Negative selection: T cells that recognize self-antigens strongly ar
e eliminated to prevent autoimmunity.
Incomplete process: Central tolerance is not always perfect, and so
me autoreactive T cells may escape this selection process. This can l
ead to the development of autoimmune diseases.
Peripheral Tolerance: Maintaining Immune H
omeostasis
https://www.studyfetch.com/platform/studyset/6748730d72bff04b73915866/material/67864b89e9fc3843c44dcfe5/document 20/1/25, 14:41
Page 1 of 4
, Peripheral tolerance refers to mechanisms that operate outside the
thymus and bone marrow to prevent autoimmunity. These mechanis
ms are essential for maintaining immune homeostasis and preventi
ng the activation of autoreactive immune cells.
Immunologically privileged sites: Certain tissues, such as the brain,
anterior chamber of the eye, testis, and uterus, are considered immu
nologically privileged. These sites are protected from immune attack
by various mechanisms, including:
Lack of lymphatic drainage: This prevents the migration of immun
e cells to these sites.
Presence of physical barriers: These barriers, such as the blood-br
ain barrier, restrict the entry of immune cells.
Secretion of immunosuppressive factors: These factors suppress t
he activity of immune cells.
Immunologic ignorance: This refers to the sequestration of self-anti
gens by autoreactive clones, preventing their recognition by the imm
une system.
Anatomical Barriers: The Blood-Brain Barrier
(BBB)
The BBB is a highly selective barrier that protects the central nervous
system (CNS) from harmful substances. Only specific molecular sub
stances can pass through the BBB.
Break of anatomical barriers triggers autoimmunity: In multiple scl
erosis, the BBB is disrupted, allowing immune cells to infiltrate the CN
S and attack myelin, leading to neurological damage.
Fas-FasL Interactions: A Crucial Checkpoint f
or Immune Cell Survival
Fas (CD95) and FasL (CD95L) are proteins involved in apoptosis, a pr
ogrammed cell death process.
Mutations in Fas/FasL genes lead to autoimmunity: Mice with mutat
ions in the Fas or FasL genes develop autoimmune diseases, such as
systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), Sjögr
en's syndrome (SS), and autoimmune lymphoproliferative syndrome
(ALPS).
https://www.studyfetch.com/platform/studyset/6748730d72bff04b73915866/material/67864b89e9fc3843c44dcfe5/document 20/1/25, 14:41
Page 2 of 4
