Effects of cystic fibrosis serum on the rat parotid gland.

Injections of serum from human patients with cystic fibrosis into adult rats 
caused pronounced structural modifications and increased mitotic rate in the parotid 
gland. Mitotic rate was increased from a low level of 0.02/1,000 
acinar cells in parotid glands of adult rats to 6.5/1,000 acinar 
cells after 2 or 3 days of serum injection. At the 
light and electron microscopic levels, significant acinar cell atrophy and degranulation 
were observed. Cellular necrosis, and increases in quantity of lysosome-like dense 
bodies, mast cells, and macrophages were also detected. These changes are 
suggestive of tissue response to injurious foreign protein. Furthermore, the fact 
that normal sera pronounced the same kind of effects (but greatly 
reduced in extent) strengthens the view that these effects result from 
the immunologic response of the host organ to foreign antigen. Since, 
however, the responses of the rat parotid to cystic fibrosis serum 
were considerably more marked than those elicited by normal serum, the 
rat parotid may thus have potential usefulness in assaying for the 
presence of human cystic fibrosis factor. 