Suppression of the Insect Immune System by Parasitic Hymenoptera

Abstract

The invertebrate immune system remains poorly characterized. Although some of the mechanisms are just beginning to be examined, it is nonetheless clear that the vertebrate antigen-antibody system is not operational in invertebrates. Among the invertebrates, the class Insecta has received the greatest attention. But, in spite of extensive research, the immune system of insects is still poorly understood. It is not the purpose of this chapter to review the invertebrate or the insect immune system, as excellent reviews exist (Lackie 1988; Dunn 1986) and several edited books are available on the subject (Brehelin, 1986; Gupta, 1986), but rather to examine how parasitoids suppress the immune system of their insect host. As Bayne (1984) stated, understanding how parasites (parasitoids) can deal with the immune system of their host provides information on how the immune system functions. Thus what is known about the ability of parasitoids to suppress the insect immune system and some methods of study are examined here. However, before these topics are taken up, some background on the response of the insect immune system to parasitoids is required.