This document discusses immunological tolerance and autoimmune diseases. It explains that the immune system can develop an immune response or enter a state of tolerance upon encountering an antigen. Tolerance is the lack of an immune response to antigens the body has the potential to respond to. Both immune responses and tolerance involve the same cellular and molecular components, differing only in the effector phase. Careful regulation of targeting versus tolerating responses is needed to avoid autoimmunity or failure to respond to pathogens. The document outlines different mechanisms of passive and active tolerance, including central tolerance in the thymus, peripheral tolerance, and oral tolerance through exposure to antigens in the gut.

1. Immunopatology of
autoimmune diseases
Immunological tolerance
Cellular and molecular mechanisms of the
immunological tolerance

2. Tolerated skin grafts on MHC (H2) identical mice

3. TOLERANCE & AUTOIMMUNITY
• Upon encountering an antigen, the immune system
can either develop an immune response or enter a
state of unresponsiveness called tolerance.
• Immunological tolerance is thus the lack of ability to
mount an immune response to epitopes to which an
individual has the potential to respond.
• Targeting type and tolerating type immune
responses composed by the same cellular and
molecular components, the differences are in the
effector phase only.
• Targeting type immune response or tolerance
needs to be carefully regulated since an
inappropriate response –whether it be autoimmune
reaction to self-antigens or tolerance to a potential
pathogen– can have serious and possibly life-
threatening consequences.

5. TOLERNACE
- PASSIVE
- ACTIVE
AUTOIMMUNITY
- PHYSIOLOGIC REGULATION
- AUTOIMMUNE DISEASES

6. Passive tolerance
Unresponsiveness: no MHC recognition or
inhibited cellular differentiation.
• Tolerance induced by the nature
of the antigen
• Tolerance induced by the body

7. Passive tolerance induced by the
nature of the antigen
• chemical nature
• dose of the antigen
- low dose tolerance (T cell mediated,
long ranging)
- high dose tolerance (B cell mediated,
short ranging)
• mode of the administration

8. T-cell tolerance
– Central Tolerance (selection in the Thymus)
– Peripheral Tolerance
• Lack of Co-stimulation
• Failure to Encounter Self Antigens
• Receipt of Death Signal
• Control by Regulatory T cells

9. Failed co-stimulation results low dose
tolerance

13. Anergy
Deletion
Anergy
No response

14. B-cell Tolerance
- Central tolerance
- Peripheral tolerance

16. Oral tolerance
Fed antigens can cross the intestinal
epithelial-cell barrier in several ways.
Antigens can be processed and
presented on MHC molecules by
intestinal epithelial cells (a) or cross
through the epithelium, where they are
absorbed into capillaries (b) that drain
into the portal vein and the liver.
Antigens can also be captured by
macrophages (c) and carried to local
draining lymph nodes in lymphatics.
Dendritic cells have recently been
shown to be capable of extending
processes into the gut lumen (d), where
they can capture antigen directly, which
would then allow them to carry antigen
to the local mesenteric lymph node in
lymphatics. Each of these pathways
ultimately converge at the spleen. It
is possible that many redundant
pathways exist to generate tolerance or
that each individual pathway generates
different forms of tolerance to specific
antigens. TCR, T-cell receptor.

19. Tolerance induced by the body
• sequestered antigens
no MHC recognition
no antigen presentation
no systemic response
• heredited or acquired immunodeficiency
• clonal anergies
• tolerance induction

20. ACTIVE TOLERANCE
Anti-idiotype network
• Anti-idiotype antibodies against T cell and B
cell receptors and immunoglobulins
• Antigen-specific inhibition and induction of
memory
• Part of the adaptive immune response
“Immunological homunculus”
• Natural (auto)antibodies: low affinity IgM
autoantibodies produced by CD5+ B cells
• γ/δ T cells
• Innate-like adaptive responses

21. Antigens recognized by natural
antibodies
Heatshock
proteins
hsp65, hsp70, hsp90, ubiquitin
Enzymes aldolase, citockrom c, SOD,
NAPDH, citrate synthase,
topoisomarase I.
Cell membrane
components
2-microglobulin, spectrin,
acetylcholin receptor
Cytoplasmic
components
actin, myosin, tubulin, myoglobin,
myelin basic protein
Nuclear
components
DNS, histones
Plasma proteins albumin, IgG, transferrin
Cytokines,
hormones
IL-1, TNF, IFN, insulin,
thyreoglobin