The avian lung-associated immune system: a review

Area of Science:

• Immunology
• Avian Pathology
• Respiratory System Research

Background:

• The avian lung is susceptible to viral and bacterial diseases.
• Birds possess a complex lung-associated immune system for defense.
• Bronchus-associated lymphoid tissue (BALT) is a key component of this system.

Purpose of the Study:

• To review the structural and functional characteristics of the avian lung immune system.
• To discuss the development and organization of avian bronchus-associated lymphoid tissue (BALT).
• To highlight the cellular and humoral defense mechanisms in the poultry respiratory tract.

Main Methods:

• Literature review of avian lung immunology.
• Description of BALT development and structure.
• Analysis of immune cell distribution and function in the avian lung.

Main Results:

• Avian BALT develops post-hatching and features distinct T and B cell zones with germinal centers.
• The avian lung interstitium contains macrophages and lymphocytes, with few macrophages on the respiratory surface normally.
• Live bacterial challenge induces macrophage and heterophil efflux, alongside secretory IgA on the lung surface.

Conclusions:

• The compartmentalized immune system of the avian lung, including BALT, plays a crucial role in host-pathogen interactions.
• Understanding the distinct functional properties of BALT and non-BALT regions is vital for studying avian respiratory diseases.
• Avian lung immunity involves both cellular (macrophages, lymphocytes, heterophils) and humoral (secretory IgA) components.