Specificity of Chicken (IgY) versus Rabbit (IgG) Antibodies Raised against Cholecystokinin Octapeptide (CCK-8).

Antibodies produced in chickens (egg yolk Antibody-IgY) and rabbits against CCK-8 TyrSE (a C-terminal extended CCK-version) were compared with respect to their specificity against several modified CCK-sequences by means of radioimmunoassay and spot blot assay. The content of neuronal CCK was determined by using both an "avian" and a "mammalian" RIA. The IC50 values obtained indicate differences between the binding capacity of rabbit and chicken Antibody, respectively. Supported by the data from spot blot assay, it appears, that the avian Antibody binding activity was directed primarily towards short CCK-sequences whereas the longer sequences are less well recognised in contrast to the mammalian antibody. Probably, these differences may be due to characteristics regarding the shape of the molecules (caused also by fixation processes necessary for blotting procedures) as well as to structural differences between avian and mammalian antibodies itself (both antibodies originate from quite different immune systems). By comparing the quantitative CCK data (avian versus mammalian RIA) a significant correlation could be observed. Immunohistochemical studies using avian antibodies revealed a neuronal CCK pattern different from those using rabbit antibodies. These results are discussed on the basis of the specificity studies.