LECTINS AS DEFENSE MOLECULES IN VERTEBRATES AND INVERTEBRATES

The use of lectins for detecting structural variations in the glycocal yx of interacting cells is common to all forms of life, and forms the basis for their function in fertilisation, development, leucocyte migr ation and self/non-self distinction. Six lectin families are recognise d; legume lectins, cereal lectins, P-, S- and C-type lectins, and pent raxins. Of the latter four occurring in animals, only pentraxins and C -type lectins are implicated in defence. Pentraxins have been describe d fi om the horseshoe crab and tunicates, as well as trout and Xenopus . C-type lectins are known from at least four protostome and three deu terostome invertebrates. A role in defence is strongly implicated for at least some of these. The C-type molecules known from lower vertebra tes have generally lost their lectin function and exist as antifreeze proteins in fish and as a component of snake venom. However, a factor with structural and functional resemblance to mammalian mannan-binding protein (MBP) has been described from the Atlantic salmon, Salmo sala r. For a more complete understanding on the evolution of mammalian C-t ype lectins, attention should be paid not only to humoral but also mem brane bound lectins and extracellular matrix components in invertebrat es and lower vertebrates. (C) 1996 Academic Press Limited