An agricultural worker experiences difficulty breathing which becomes progressively worse. Tests show inflammation and damage of the lung tissue, but IgE antibodies and granulocytes are in the normal ranges.
With which disorder of the immune system are these signs and symptoms consistent?

A) allergic reaction
B) acquired immunodeficiency
C) autoimmunity
D) type III (immune complex-mediated) hypersensitivity
E) type IV (delayed) hypersensitivity

The correct answer is option D, that is, type III immune complex-mediated hypersensitivity.

Explanation:

When an individual's immune system works in such a manner that it eventually results in self-destruction signifies that the person is suffering from hypersensitivity. There are different kinds of hypersensitivities, that is, four in total, in which the IIIrd type, that is, type III hypersensitivity reaction takes place when the complexes of antigen and antibody get accumulated in the walls of blood vessels destroying tissues and inflammation.  

Thus, it is clear that it is the immune complexes, which mediate the type III hypersensitivity reactions, and the complex is formed of antibody and antigen. In type III hypersensitivity reaction, the formation of immune complexes is done when antibodies combine with soluble antigens. An illustration of type III hypersensitivity is the autoimmune disease systemic lupus erythematosus.  

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