Avian macrophages: contribution to cellular microenvironment and changes in effector functions following activation.

The capacity of macrophages to generate metabolites and monokines having effector and regulatory functions can result in a major impact on their cellular microenvironment. Macrophage products synthesized in response to bacterial lipopolysaccharide stimulation include reactive oxygen and nitrogen intermediates as well as tumor necrosis factor (TNF). These secreted products of macrophages exhibit bioactivity either locally or systemically. Although the mechanism of action of avian monokines such as TNF-like factor may be similar to their mammalian counterparts, chicken TNF seems to lyse cells of chicken origin and not of mammalian origin. Furthermore, the generation and activity of products such as TNF is directly influenced by environmental stressors such as heat and toxins.