Hypersensitivity type III

Immune complex-mediated (Type III) Hypersensitivity
Learning objectives: At the end of lecture, The students should be able to:
1-Define immune complex-mediated (Type III) Hypersensitivity.
2-Mention the types of immune complex.
3-Mention the types of antigens that cause immune complex-mediated injury.
4-Enumerate the types of immune complex-mediated disease.
5-Identify the phases of systemic immune complex-mediated disease.
6-Enumerate the factors that influence immune complex deposition.
7- Describe the histopathological features of immune complex injury.
8-Discuss the pathogenesis of local immune complex disease ( Arthus reaction)

Immune complex-mediated (Type III) Hypersensitivity
-Definition of immune complex-mediated (Type III) hypersensitivity.
-Examples.

Immune complex
*Types of immune complex
1-Circulating immune complex(e.g. acute serum sickness).
2-In situ immune complex(e.g. form of glomerulonephritis).

Antigens of immune complex-mediated Hypersensitivity
-Types of antigens:
1- Exogenous antigens(such as foreign protein, bacteria, and viruses).
2-Endogenous antigens (self antigens).

Immune complex-mediated disease
-Types :
1- Generalized(systemic) immune complex disease (such as acute serum
sickness).
2- Local immune complex disease(Arthus reaction) (e.g. glomerulonephritis,
and arthritis).

Phases of systemic immune complex-mediated disease
-Phases:
1-Formation of antigen-antibody complex in the circulation.
2-Deposition of the immune complexes in various tissues.
3- An inflammatory reaction at sites of immune complex deposition.

Factors influence immune complex deposition
-Factors:
1-Size of immune complex.
*Small-sized immune complex.
*Intermediate-sized immune complex.
*large-sized immune complex.
2-Functional status of the mononuclear phagocyte system.
3-Others:
-Charge of the immune complexes(anionic versus cationic)
-Valency of antigens.
-Avidity of the antibodies.
-Affinity of the antigen to various tissue component.
-Lattice(Three-dimensional structure of the complexes.
-Hemodynamic factors.

Histopathological features of immune complex injury
-Histopathological features:
1- Necrotizing vasculitis.
2- Infiltration of neutrophils.
3- Fibrinoid necrosis.

Local immune complex disease(Arthus reaction)
-Definition.
-Mechanism.

Morphological changes(Arthus reaction)
-Morphological changes:
1-Necrosis.
2-Inflammatory reaction.

Questions
1-Discuss the mechanism Of acute serum sickness.
2-Explain the mechanism of poststreptococcal glomerulonephritis.
3-Draw by arrows the pathogenesis of immune complex-mediated tissue
injury.
4-Write short notes on of serum sickness(History and pathology)

* References:
• ___________
• 1-MacSween R.N.;and Whaly K.(Murs Textbook of pathology); 13th
edition,Arlond.1997.
• 2-Kumar V.;Abbas A.; and Fausto N.(Robbin and Cortan, Pathologic basis of
disease).7th edition. Elsevier Sounder. 2004.
• 3-Rosal J. (Ackerman s surgical pathology); 9th edition.Mosby.2003.
• 4-Walts J.B.,Talbot L.c.(general pathology ); 7th edition ,Churchill
Livingstone; 1996 .
• 5-Krishna V.(Text book of pathology );Orient Longman Private limited. 2004
.