Abstract
Local respiratory-tract infection was produced experimentally in guinea-pigs by intranasal instillation of a suspension of parainfluenza virus type 3. Histologically, interstitial pneumonitis developed within 10 days and persisted for at least 70 days. Cell-mediated immunity was measured at intervals for 70 days after infection. Dermal reactivity could not be elicited. Leucocyte-migration inhibition and macrophage-migration inhibition were increased. Macrophage aggregation was present. Increased cell-mediated immunity could be transferred from infected donor animals to normal recipient animals by adoptive spleen-cell transfer even 60 and 70 days after infection.