autoimmunity-definition classification types of autoimmunity

1. EMANI APARNA
SRINIVAS COLLEGE OF
PHARMACY
AUTO-IMMUNITY

2. Autoimmunity is a state in which body’s immune
system fails to distinguish between self and non-self
and reacts by formation of auto-antibodies against
one’s own tissue organisms.
MECHANISMS:
 Immunological factors: Failure of immunological
mechanisms of tolerance initiates autoimmunity.
These mechanisms are as follows:
1. Polyclonal activation of B cells
2. Generation of self reacting B cell clones.
3. Decreased T suppressor and increased T helper
cell activity.
4. Sequestered antigen released from tissues.

3.  Genetic factors:
The role of genetic factors in the pathogenesis of autoimmunity are as
follows:
1. Tissues are involved in autoimmunity shows increased expression of
class II HLA antigen.
2. Some of the autoimmunity disorders show increased familial
incidence.
 Microbial factors
Infections with microorganisms, specifically viruses and rarely bacteria
and mycoplasma. All these microrganisms play a role in the
pathogenesis of autoimmunity.

4. CLASSIFICATION OF AUTOIMMUNE DISEASES
1. ORGAN SPECIFIC DISEASES: In these disorders, the
autoantibodies that are formed reacts against a specific
organ tissue component resulting in its destruction.
2. NON-ORGAN SPECIFIC DISEASES: A large no of
autoantibodies are formed which reacts with several tissues
and hence causes systemic lesions.
Egs: systemic lupus erthematosus, Rheumatoid arthritis,
Sclerodoma , Polymositis, dermatomyositis, Polyorteritis
nodosa(PAN), reiter’s syndrome, mixed connective tissue
disease.

5. SYSTEMIC LUPUS
ERYTHEMATOSUS
 SLE is the classical example of systemic
autoimmune or collagen diseases.
 An inflammatory disease caused when the
immune system attacks its own tissues.
 It is a skin disease due to the production of
antinuclear factor (ANF) or antinuclear auto Ab
 ANF reacts with the breakdown products of nuclei
in the normal wear & tear of cells & form immune
complexes which cause the tissue damage.
 In these patients, LE cell (a mature neutrophil)
appears in blood & bone marrow.

6. 2 forms of Lupus erythematosus are described:
Systemic or disseminated form:
 is characterized by acute and chronic
inflammatory lesions widely scattered in the body.
 There is presence of various nuclear and
cytoplasmic auto antibodies in the plasma.
Discoid form:
 Is characterized by chronic and localized skin
lesions involving bridge of nose and adjacent
cheeks.

7. CHARACTERISTICS OF SLE
 It is a systemic disease affecting the whole
body.
 Appearance of blood red spots over the bridge of
nose & cheeks. The lesions take the shape of a
butterfly.
 Connective tissues of the skin, kidney, heart,
spleen & blood vessels are severely damaged
resulting in joint pain, fever & anaemia.
 Glomerulonephritis ( acute inflammation of kidney
mainly due to immune response) due to
deposition of immune complex in the glomerulus
region.

8. The source of autoantibodies as well as
hypergammaglobulinaemia in SLE is the
polyclonal activation of B cells brought about by
following dearrangements:
 Immunologic factors. These include:
1. An inherited defect in B cells
2. Stimulation of B cells by microorganisms
3. T helper cell hyperactivity
4. T suppressor cell defect.

9.  Genetic factors:
Genetic prediposition to develop autoantibodies to
nuclear and cytoplasmic antigens in SLE-
immunoregulatory function of class II HLA genes
implicated .
 Other factors: various other factors express the
genetic susceptibility of an individual to develop
clinical disease. These factors are:
1. Certain drugs.Eg: pencillamine D
2. Certain viral infections e.g: EBV infection
3. Certain hormones e.g: oestrogen

10. PATHOGENESIS
The autoantibodies formed by any of the
mechanisms explained above are the mediators
of tissue injury in SLE.
Two types of immunologic tissue injury can occur in
SLE:
1. Type II hypersensitivity: formation of
autoantibodies against blood cells results in
haemotologic derangement in SLE.
2. Type III hypersensitivity- antigen-antibody
complex which is deposited in various renal
glomeruli walls of blood vessels.

11. RHEUMATOID ARTHRITIS
 It is a chronic systemic disease of the joints
 Caused by the auto Antibody of IgM type, called
as rheumatoid factors.
Characteristics:
 The synovial fluid of these patients contain
increased no. of T-cells & macrophages.
 Marked by inflammatory changes in the synovial
membrane & by atrophy of bones.
 In later stage, deformity & ankylosis develops.

12. MYASTHENIA GRAVIS
 Myasthenia gravis is believed to be caused by
variations in certain genes. The disorder occurs when
the immune system malfunctions and attacks the
body's tissues. The antibody in myasthenia gravis
attacks normal human protein, targeting a protein
called an acetylcholine receptor, or a related protein
called a muscle-specific kinase.
 The thymus gland cells form part of the body's
immune system. In those with myasthenia gravis, the
thymus gland is large and abnormal. It sometimes
contains clusters of immune cells which indicate
lymphoid hyperplasia.
 Human leukocyte antigens have been associated with
MG susceptibility. Many of these genes are present
among other autoimmune diseases. Relatives of MG
patients have a higher percentage of other immune
disorders.

13. POLYMYOSITIS-
DERMATOMYOSITIS
This disease is a combination of symmetric
muscle weakness and skin rashes.
PATHOLOGIC CHANGES:
 The skeletal muscles usually affected are of
pelvis, shoulders, neck, chest and diaphragm.
 Histologically, fragmentation of muscle fibres and
numerous inflammatory cells are present. In later
stage muscle fibres are replaced by fat and
fibrous tissue.

14. SJOGRENS SYNDROME
 This syndrome is characterised by the trial of dry
eyes, dry mouth and rheumatoid arthritis.
PATHOLOGIC CHANGES:
 In early stage lacrimal and salivary glands show
periductal infiltration by lymphocytes and plasma
cells, which at times may form lymphoid follicles.
 In late stage glandular parenchyma is replaced by
fat and fibrous tissue.

15. Clinical features
 Symptoms referable to eyes: blurred, burning and
itching
 Symptoms referable to xerostomia: dryness
fissured oral mucosa and difficulty in swallowing.
 Symptoms of glandular involvement: enlargement
and inflamed lacrimal gland.

16. REITER SYNDROME
 This syndrome is characterised by traid of
arthritis, conjunctivitis, and urethritis.
 There may be mucocutaneous lesions on palms,
soles, oral mucosa and genitalia.
 Antinuclear antibodies and RA factor are usually
negative.

17. ADDISONS DISEASE
 It is due to adrenocortical damage & hence
insufficient secretion of adrenal hormones.
 Tissue damage is caused by auto Ab against
zona glomerulosa cells of adrenal cortex.