Type (II) Hypersensitivity. ( ( cytotoxic hypersensitivity ) Antibody directed against cell surface or tissue antigens interacts with complement and a.

Type (II) HypersensitivityType (II) Hypersensitivity..

((cytotoxic hypersensitivity ) Antibody directed against cell surface or Antibody directed against cell surface or

tissue antigens interacts with complement and tissue antigens interacts with complement and a variety of effecter cells to bring about damage a variety of effecter cells to bring about damage to the target cells. to the target cells.

Drug-induced hemolytic anemia, Drug-induced hemolytic anemia, granulocytopeniagranulocytopenia and and thrombocytopeniathrombocytopenia are are such examples.such examples.

The reaction time is minutes to hours.The reaction time is minutes to hours.

The antigens are normally endogenous,

although exogenous chemicals (haptens) which can attach to cell membranes .

IgG and IgM mainly antibody that react in type

(II) hypersensitivity.

Phagocytes and K cells may also play a role (ADCC).

The lesion contains antibody, complement and neutrophils

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Hypersensitivity type (II) are triggered by Ab reacting with antigenic determinants which form part of the cell membrane

This is the normal appearance of the thyroid gland on the anterior trachea of the neck. The thyroid gland has a right lobe and a left lobe connected by a narrow isthmus.

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• HashimotoHashimoto‘s thyroiditis initially ‘s thyroiditis initially cause thyroid enlargement.cause thyroid enlargement.

• Later there may be atrophy and Later there may be atrophy and fibrosis.fibrosis.

• The gland appears firm, fleshy and The gland appears firm, fleshy and palepale

This symmetrically small thyroid gland demonstrates atrophy. This patient was hypothyroid. This is the end result of Hashimoto's thyroiditis. Initially, the thyroid is enlarged and there may be transient hyperthyroidism, followed by a euthyroid state and then hypothyroidism with eventual atrophy years later.

Hashimoto‘s thyroiditis. The gland is slightly enlarged and the lobes have been sliced to show the uniformly pale and fleshy cut surface.

HistopathologicallyHistopathologically

- - The gland is denesely infiltrated byThe gland is denesely infiltrated by

lymphocytes and plasma cells. lymphocytes and plasma cells.

- Lymphoid follicle formation.- Lymphoid follicle formation.

- Colloid center is reduced.- Colloid center is reduced.

- Thyroid epithelial cells show change in - Thyroid epithelial cells show change in

which they enlarge and develop which they enlarge and develop eosinophilic eosinophilic

granular cytoplasm (granular cytoplasm (HHürthle cellsürthle cells).).

- In advance case fibrosis- In advance case fibrosis

Thyroid with Hashimoto's thyroiditis ,the lymphoid follicle at the right center. This is an autoimmune disease and often antithyroglobulin and antimicrosomal antibodies can be detected.

This high power microscopic view of the thyroid with Hashimoto's thyroiditis demonstrates the pink Hurthle cells at the center and right. The lymphoid follicle is at the left. Hashimoto's thyroiditis initially leads to painless enlargement of the thyroid, followed by atrophy years later.

Histological features of Hashimoto‘s thyroiditis. There is destruction of follicles by a dense lymphocytic infiltrate with germinal center formation (right). Some of the surviving epithelial cells show Hurthle cell change (lower left).