These complexes enable the detection of different distribution at the membrane's inner and outer surface. It can therefor not be said without further analysis whether the receptor is an oligo- or a polysaccharide, a glycoprotein or a glycolipid. Lectins detect only a rather small range of sugars. There exist no lectins that detect, for example, arabinose or xylose residues. Antibodies are a rather homogeneous group of proteins that occur in the serum of vertebrates protecting the animal from foreign influences like infections with bacteria or viruses or from tumour cells.
Plants have no antibodies.
Such a signal has to be of a macromolecular nature. It may be part of a cell surface. A component that induces antibody production is called antigen . An antigen is usually bigger than the respective binding site of the antibody. The antibody-binding domain of the antigen is called an antigen determinant .