Cellular recognition of foreign-ness in two insect species, the American cockroach and the desert locust.

Encapsulation of tissue implants by haemocytes was used as the assay for immune recognition in the insects studied. If haemocytes attach to and encapsulate an object implanted within the haemocoele, it may be assumed the implant is recognized as 'not-self'; lack of encapsulation of tissue implants may be assumed to indicate lack of recognition. The American cockroach, Periplaneta americana, and the desert locust, Schistocerca gregaria, were used both as donors of tissue, and as recipients of tissue implants from various insect species. Allografts were not recognized as foreign and encapsulated by haemocytes of either S. gregaria or P. americana, a phenomenon which has been reported frequently for other insect species. Haemocytes of S. gregaria recognized and encapsulated a smaller range of xenografts compared with haemocytes of P. americana, and it appears that the acuity of immune recognition by haemocytes differs between S. gregaria and the other species tested. Reasons for the different recognition responses of P. americana and S. gregaria are suggested and discussed with particular reference to the results for Nauphoeta cinerea tissue in P. americana, and Gryllus domesticus tissue in S. gregaria, where at least half the number of implants are totally but weakly encapsulated, and it is suggested that haemocytes do not react to 'difference' unless it surpasses a certain threshold.