Time course of histologic lesions of acute irritant-induced asthma at different intervals after exposure

Interval after exposure
Case 1
60 hours	15 days	60 days	150 days
Superficial fibrinohemorrhagic layer replacing bronchial epithelium that has sloughed	Persistence of hemorrhage, bronchial epithelium sloughing; increased deposition of collagen	Regeneration of epithelial cells (basal); collagen deposition; spots of lymphocytes; few PMNs; increase in thickness of basement membrane	Complete regeneration of the epithelium layer; numerous basal cells indicating regeneration
Case 2
45 days		98 days
Severe damage of the epithelial layer with few remaining basal cells; subepithelial edema with inflammatory cells underneath the basement membrane		Incomplete regeneration of the epithelial layer with few ciliated cells; inflammatory cells persisting in epithelium and connective tissue

PMNs: polymorphonuclear leukocytes.

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