Autoimmunity involves immune responses against self-antigens, leading to conditions where the immune system attacks healthy tissue, such as Graves’ disease, Hashimoto’s thyroiditis, and systemic lupus erythematosus. Causes of autoimmune diseases include sequestered antigens, neo-antigens, loss of tolerance, and cross-reacting antigens. Various types of autoimmune disorders can be classified as hemolytic, localized, or systemic, with distinct laboratory diagnostics for conditions like SLE and rheumatoid arthritis.

1. Autoimmunity
DR.PRINCE C P
HOD & Associate Professor
Department of Microbiology,
Mother Theresa
Post Graduate & Research Institute of Health Sciences
(Government of Puducherry Institution)
Pondicherry

2. Autoimmunity
 Autoimmunity is defined as the
presence of immune response of auto
Antibody against self Antigen.
 It can be a humoral or cell mediated
immune response against the
constituents of the body’s own tissues.

3. Autoimmune disorder
 An autoimmune disorder is a condition
that occurs when the immune system
attacks and destroys healthy body
tissue

4. Autoimmunity
 Graves’ disease
 Hashimoto’s thyroiditis
 Addison’s disease
 Myasthenia gravis
 SLE
 Diabetes mellitus type 1

5. Auto or self antigens
 Are antigens that presents in ones
own cells
 Are altered by the action of bacteria,
viruses, chemicals or other drugs
Auto antibodies
 Altered cell (Auto Ag) - elicits the
productions of Antibody

8. Causes of autoimmune diseases
1. Sequestered or Hidden antigens
 Ag in the secluded places - are not
accessible to the immune system.
 E.g. Lens Ag, Sperm Ag, etc.
2. Neo antigens
 Altered or Modified Antigens – by
physical (irradiation), chemical (drugs)
or microbial agents ( intracellular viruses)
3. Cessation of Tolerance
 It may result when tolerance to the self-
Ag is abrogated.

9. Causes of autoimmune diseases
4. Cross reacting Antigens
 A foreign Ag which resembles self a 2nd
Ag
 Many species share organ specific Ags.
 E.g. Ag of Human brain & Ag of sheep
brain, Streptococcal M protein & Heart
muscles, Nephritogenic strains of
Streptococci Ags & Renal glomeruli
shares similar epiotes.
5. Loss of Immunoregulation
 Loss of Self tolerance - caused by over
activity or lowered activity of T and B-
cells

10. Classification of autoimmune
disorders
 1. Haemolytic autoimmune diseases
 2. Localised autoimmune diseases
 3. Systemic autoimmune diseases

12. Myasthenia Gravis
• 80 to 90% of patients have Autoantibodies
against acetylcholine receptor
• Combination of the Abs to the receptors blocks
the binding of acetylcholine which destroy the
receptors
• Muscle weakness
• Repetitive movements very difficult!
• In particular eye bulb muscles affected
• Life threatening when muscles for respiration
are affected
• Can be transferred to foetus .
• Abs can be detected with RIA methods
Anti-cholinesterase agents are employed in
therapy

13. Grave’s Disease
• Autoantibodies against receptor for
thyroid stimulating hormone (TSH)
• Activate receptor leading to excessive
thyroid hormone production
• Women are more susceptible than
men by a margin of 7:1 and usually
present between the ages of 30 and
40.

14. Systemic Lupus
Erythematosus
 It is a chronic systemic inflammatory disease
marked by alternating exacerbation and
remissions
Approximately 1 in every 2000 individuals are
affected
Age of onset is usually b/w 20 and 40 yrs of
age
Women are much more likely than men to be
stricken by a margin of 13 to 1
 Etiology is unknown but may be due to
genetic and environmental factors
Auto-antibodies against nuclearcomponents
(DNA, histones,ribosomes, snRNP, etc)
Local inflammation in skin, joints and
kidneys, multi-organ damage

15. Laboratory Diagnosis of SLE:
 A screening test for antinuclear antibody
(ANA) is usually the first test done
 Double-stranded DNA (ds-DNA):These Abs
are the most specific for SLE and are seen
only in patients with SLE
 Antihistone antibody: Histone is a major
component of chromatin, This antibody is
found in lupus patients
 Anti-Sm antibody:
 Antibody to extractable nuclear antigen was
first described in a patient named Smith
hence it is called anti-Sm

16. Rheumatoid Arthritis
 Rheumatoid arthritis is a systemic
autoimmune disorder
 It involves the synovial membrane of
multiple joints
 Women are more likely to be affected
than men and usually strikes between
the ages of 20 and 40
 The main immunologic finding is the
presence of RF
 RF is a 19S Ab directed against the Fc
portion of IgG(Rheumatoid Factor/RA
factor)

17. Rheumatoid Arthritis

18. THANK YOU