Lectins as possible candidates towards anti-microbial defense in silkworm, <i>Bombyx mori</i> L

Abstract

Unlike vertebrates, insects do not have acquired immunity and therefore rely totally on innate immunity towards defense against invading microorganisms. Insect innate immunity consists of cellular and humoral reactions and both reactions work in concert in preventing insects acquiring infections. The most likely candidates for recognizing foreign material in insects are the lectins, which have already been shown to be important in mammalian innate immunity. Several reports of endogenous serum lectins having opsonic activity for invading pathogens have been circumstantiated in several insect specimens and therefore have been continuously explored for binding to wide range of microorganisms, obviating the necessity of antibodies in these animals. Silkworm, Bombyx mori L. is an important economic insect with unparalleled significance to the prosperity of weaker sections of the society and also has been promoted as a powerful laboratory model involving basic research in biology. It therefore merits immediate attention towards proper understanding of host-pathogen interactions, defensive mechanisms evolved in the host body in response to infection, anti-defensive molecules released by pathogen to suppress host immunity before reflecting on aspects of disease control. In this regard, lectins have been implicated as pattern recognition molecules serving as biosensors for detecting carbohydrate components on the microbial cells, thus triggering signaling cascade for immune activation. Understanding of such silkworm agglutinins, most specifically their binding specificities and pattern of recognition with identifiable gene families have been discussed towards establishment of its candidate role as immune defense molecules.

Key words: Bombyx mori, lectins, innate immunity, carbohydrate-binding domains.