CELLULAR-RESPONSE OF THE RESPIRATORY-TRACT OF CHICKENS TO INFECTION WITH MASSACHUSETTS-41 AND AUSTRALIAN T-INFECTIOUS BRONCHITIS VIRUSES

Cellular response of chickens to infection with infectious bronchitis virus (IBV) was investigated by lavage of the respiratory tract of fiv e 2-week-old specific-pathogen-free (SPF) chickens at 2, 8, 24, 48, 72 , and 96 hours postinfection (PI) with either Massachusetts 41 (IBV-M4 1) or Australian T (IBV-T) IBV. Tissue response was monitored by micro scopic examination of trachea and lung from five non-lavaged infected chickens collected at the same intervals. The total number of cells re covered by lavage from IBV-M41-infected chickens was dramatically high er than the total number recovered from IBV-T-infected chickens and un infected controls. By contrast, the total number of cells recovered fr om IBV-T-infected chickens was no higher than that of the uninfected c hickens. Heterophils constituted the majority of inflammatory cells re covered from both IBV-M41-infected and IBV-T-infected chickens. Hetero phil numbers in IBV-M41-infected chickens paralleled total cell-number recovery, whereas heterophil numbers in IBV-T-infected birds were no higher than those in uninfected chickens. The number of lymphocytes re covered from IBV-M41-infected chickens increased 72 hours PI and conti nued to increase for the duration of the study. Lymphocyte numbers in IBV-T-infected chickens exceeded those in uninfected chickens only at 96 hours Pl. The number of lavage macrophages in IBV-M41-infected chic kens increased earlier than the number of. lymphocytes but later reach ed a plateau. IBV-T macrophage numbers did not exceed those Tissue dam age occurred most consistently in the trachea and occurred when lavage heterophil numbers were rising or at their peak. Lavage cell recovery and composition reflected tracheal mucosa inflammatory cell infiltrat e.