More on the significance of Farmer's Lung

[Guest guest]

More on Farmer's lung which is a Type III hypersensitivity reaction. As is

aspergillosis. Note, it is acknowledged that type III hypersensitivity also

causes autoimmune diseases. This is from the Microbiology and Immunology

On-line, University of South Carolina, School of Medicine:

Type III hypersensitivity is also known as immune complex hypersensitivity.

The reaction may be general (e.g., serum sickness) or may involve individual

organs including skin (e.g., systemic lupus erythematosus, Arthus reaction),

kidneys (e.g., lupus nephritis), lungs (e.g., _aspergillosis_

(http://cancerweb.ncl.ac.uk/cgi-bin/omd?query=aspergillosis & action=Search+OMD)

), blood

vessels (e.g., _polyarteritis_

(http://cancerweb.ncl.ac.uk/cgi-bin/omd?query=polyarteritis & action=Search+OMD)

), joints (e.g., rheumatoid arthritis) or other

organs. This reaction may be the pathogenic mechanism of diseases caused by

many microorganisms.

The reaction may take 3 - 10 hours after exposure to the antigen (as in

_Arthus reaction_ (http://cancerweb.ncl.ac.uk/cgi-bin/omd?query=arthus) ). It

is

mediated by soluble immune complexes. They are mostly of the IgG class,

although IgM may also be involved. The antigen may be exogenous (chronic

bacterial, viral or parasitic infections), or endogenous (non-organ specific

autoimmunity: e.g., systemic lupus erythematosus, SLE). The antigen is soluble

and not

attached to the organ involved. Primary components are soluble immune

complexes and complement (C3a, 4a and 5a). The damage is caused by platelets

and

neutrophils (Figure 4). The lesion contains primarily neutrophils and deposits

of immune complexes and complement. Macrophages infiltrating in later stages

may be involved in the healing process.

..