VIRUS-INDUCED INCREASES IN BRONCHIOLAR MAST-CELLS IN BROWN-NORWAY RATS ARE ASSOCIATED WITH BOTH LOCAL MAST-CELL PROLIFERATION AND INCREASESIN BLOOD MAST-CELL PRECURSORS
Sd. Sorden et Wl. Castleman, VIRUS-INDUCED INCREASES IN BRONCHIOLAR MAST-CELLS IN BROWN-NORWAY RATS ARE ASSOCIATED WITH BOTH LOCAL MAST-CELL PROLIFERATION AND INCREASESIN BLOOD MAST-CELL PRECURSORS, Laboratory investigation, 73(2), 1995, pp. 197-204
BACKGROUND: Parainfluenza type 1 (Sendai) virus-induced bronchiolitis
during early life in rats induces increases in bronchiolar mast cells
that persist for months after infection and are associated with airway
obstruction and airway hyperresponsiveness. frown Norway (BN) rats ar
e highly susceptible, and Fischer 344 (F344) rats are relatively resis
tant to, Sendai virus-induced increases in airway responsiveness and m
ast cell density. EXPERIMENTAL DESIGN: To identify mechanisms responsi
ble for the virus-induced mast cell increases, BN rats were studied us
ing in vivo bromodeoxyuridine labeling, in vitro culture of bone marro
w, blood, and lung mast cell progenitors (colony-forming unit-mast cel
l (CFU-MC)), and in vivo treatment with the rodent mast cell stabilize
rs disodium cromoglycate and nedocromil sodium. Bone marrow, blood, an
d lung CFU-MC were also quantitated in F344 rats. RESULTS: At 10 days
after inoculation, there was a fivefold increase (p = 0.001) in the br
omodeoxyuridine labeling index of bronchiolar mast cells in virus-inoc
ulated BN rats. Viral inoculation increased CFU-MC/ml blood greater th
an fivefold (p < 0.05) in BN rats at 10 days after inoculation, and BN
rats had greater numbers of both blood and lung CFU-MC than did F344
rats. Treatment with inhibitors of mast cell degranulation had no effe
ct on Sendai virus-induced bronchiolar mast cell increases in BN rats.
CONCLUSIONS: Virus-induced increases in bronchiolar mast cells result
from proliferation of preexisting mast cells and may be augmented by
recruitment of circulating mast cell precursors.