Molecular mimicry

1. By
SHRUSHTI JOSHI
174551

2. AUTOIMMUNITY
 Autoimmunity is the system of immune
responses of an organism against its own
healthy cells and tissues.
 It is the consequence of an immune
response against self antigens that result in
the damage and eventual dysfunctional of
target organs.

3. MOLECULAR MIMICRY
 Molecular mimicry is the occurrence of
common B or T cell reactive epitopes
between microorganisms or
environmental agents and the host, and
the pathogenic consequence of such
cross reactivity.
 It is a mechanism by which
immunological self tolerance can be
broken, leading to autoimmune disease.

5. BASIC IMMUNE RESPONSE
 Macrophages engulf antigen and break them
into fragments.
 The antigens peptides are presented by antigen
presenting cells having MHC I and MHC II.
 These cells present the protein fragment to T
cells, activating them in the process
 The activated T cells stimulate other portions of
the immune system to begin a response against
similar protein fragments.

8. REASONS
 In molecular mimicry the protein fragment
from the antigen resembles part of the self
protein.
 Also self reactive T cells are not deleted or
made tolerant in the thymus.
 Occurs in different forms like complete identity
at protein level, similarity of amino acid
sequences and structural similarity.

10. CRITERIA
 similarity between a host epitope and an epitope
in a microorganism or environmental agent
 antibodies or T cells cross-reactive with both
epitopes detected in patients with the
autoimmune disease
 an epidemiological link between exposure to the
environmental agent or microbe and the
development of autoimmune disease
 reproducibility of autoimmunity in an animal
model following sensitization with the epitopes,
infection with the microbe or exposure to the
environmental agent

11. TYPES
“Three way molecular mimicry” is thus said to
exist between peptide sequences of three
different origins:
 the MHC, which is critically involved in thymic
T cell selection
 foreign antigens which upregulate antigen
presentation and provide co-stimulation
 self or target antigens, which are recognised
by self reactive T cells

15. REFERENCES
 Molecular Mimicry as a Mechanism of
Autoimmune Disease -Matthew F. Cusick,
PhD.
 Molecular mimicry in autoimmune disease
Susan Leech.
 molecular mimicry lisa k. peterson.
 direct-ms.org-molecular mimicry
 Molecular Mimicry and Autoimmunity Lori
J. Albert,

16. THANK YOU