Figure 3
Phospholipids are hydrolyzed by phospholipase A 2 liberating arachidonic acid and Lyso-PAF, regulators of insect's immune system. Arachidonic acid is the substrate for eicosanoid production, prostaglandins via cyclooxygenase and leukotrienes via lipoxygenase. Lyso-PAF is acetylated by PAF-acetyl transferase releasing PAF that can be degraded by PAF-acetyl hydrolase that hydrolyses PAF regenerating Lyso-PAF. In the presence of dexamethasone the immune responses are inhibited due to the suppression of phospholipase A2 activity with lower production of eicosanoids and PAF. On the other hand when exogenous arachidonic acid is added there is enhancement of eicosanoid production and immune responses increase.