Chicken air sacs and mesentery: a histomorphometrical and immunological study

Fat-associated lymphoid clusters (FALCs) are novel lymphoid tissues that have been reported in the mesenteric and mediastinal fat tissue of mouse and human. It plays role in the progression of respiratory and intestinal inflammation and parasitic infestations. However, their occurrence in the chicken air sacs and mesenteric adipose tissue has not yet been identified. Here we investigated the occurrence and distribution of FALCs in the air sacs (cervical, clavicular, thoracic, and abdominal) and mesenteric adipose tissue of healthy chicken. The latter air sacs and mesentery were immediately harvest-ed after anesthesia and cutting the chicken heads then fixed in 4% paraformaldehyde fixative solution for histopathological examination. The degree of FALCs development among different specimens was measured and statistically analyzed. Our results revealed lymphoid clusters associating with the adipose tissues in mesentery, and air sacs (clavicular, thoracic, and abdominal), but not the cervical one. Interestingly, the thoracic air sacs showed significant higher FALCs size in comparison to that of other air sac types and the mesentery. Our findings suggested other possible immunological role of the air sacs and mesentery that could have impact on the progression of air sacculitis and mesenteritis-associate diseases. However, further investigations are required for clarification of air sacs and mesenteric FALCs in the progressions of respiratory and digestive tract diseases.