Insects are known to have an innate immune system that is non-specific and will attack foreign objects, such as bacteria. Innate immunity relies on hemocytes to protect against pathogens and physical damage. Hemocytes encapsulate a foreign object by congregating around the object, isolating it in order to protect the body. Insects lack adaptive immunity—the ability to recognize self from altered-self.
The house cricket undergoes flight muscle histolysis—degradation of the flight muscles, which accounts for the loss of flight. Flight muscle histolysis is recognized as a form of programmed cell death and in the latter stages, degraded tissue is removed by hemocytes. This suggests that though the house cricket may lack adaptive immunity, they are capable of recognizing altered-self. Therefore, our objective was to explore the role of hemocytes that clear degraded tissue associated with flight muscle histolysis in the house cricket.
Crickets were maintained in a colony until adult emergence. Adult females were separated and designated as Day 0, then maintained in isolated colonies by age. To measure immune response, the encapsulation rate for two groups was observed for the following: Control Group – nylon monofilaments were soaked in saline and inserted in the abdomen of Day 6 crickets. Treatment Group 1 – nylon monofilaments were soaked in the homogenates of Day 1 flight muscles, then placed in the abdomen of Day 6 crickets. Treatment Group 2 – same method as Treatment Group 1, using flight muscles obtained from Day 3 crickets. Monofilaments were removed 24 hours after insertion, photographed and mean grayscale values analyzed to determine encapsulation rate.
Preliminary data shows that there is a higher rate of encapsulation associated with muscles undergoing flight muscle histolysis, compared to that of healthy flight muscles. This indicates that though crickets have a conserved immune system, they are capable of complex responses.