Objective  To understand the immune status of chicken respiratory mucosa at different stages.

Method  The embryo of Hy-line white chickens (18- and 20-day-old), and the nose, larynx, trachea and lung of chickens at different day-age (1-, 4-, 7-, 14-, 21-, 35- and 56-day-old) were selected in this study. The occurrence, location, distribution and quantity change of IgA⁺ secreting cells were studied by immunohistochemical method.

Result  There was no IgA⁺ cell in the mucosa of each respiratory organ during the embryonic period. IgA⁺ cells were present in the nose and lung at 1-day-old age, laryngeal mucosa at 4-day-old age, and tracheal mucosa at 7-day-old age. The number of IgA⁺ cells in the respiratory mucosa of each organ increased gradually with the increase of age. The lymphoid aggregates were formed earlier in the nasal mucosa and the intersections of the primary and secondary bronchus in the lung at 4-day-old age, and formed in the laryngeal mucosa at 7-day-old age, in the tracheal mucosa at 35-day-old age. The IgA⁺ cells in these lymphoid aggregates were all mainly distributed on the periphery of the lymphoid aggregates. At 35-day-old age, there were more IgA⁺ cells in the mucosal lamina propria and the epithelium of the nose, larynx and trachea, and thus more effective and direct secretion of SIgA could be performed for mucosal immunity. At 56-day-old age, the number of IgA⁺ cells in the respiratory mucosa of the four organs reached a peak and germinal centers were formed at the mucosal bottom, which was the characteristic of mucosal associated lymphoid tissue, thus more effectively performed mucosal immune function.

Conclusion  The distribution and number of IgA⁺ cells in the respiratory mucosa of chickens show age-related changes, and the number and distribution of IgA⁺ cells in the nose, larynx, trachea and lung all reach a certain scale at 35-day-old, which can provide immune protection for the respiratory mucosa.