Abstract
Adults of four anuran amphibian species and five urodele species were immunized with a 25% suspension of horse erythrocytes. After 8 or 14 days, spleen lymphocytes were removed and their specific red cell‐binding capacities tested by immunocytoadherence. Antigen‐binding cells were classified as high‐dose nonsecretory or secretory according to whether they bound a single layer or several layers of erythrocytes. Adrenaline stimulated α and β adrenoreceptors of cells from all four anuran species, giving an α effect (a reduction in rosette formation) in the presence of β antagonists, and a β effect (an increase) in the presence of α antagonists.
Responses similar to α and β adrenergic responses were shown by samples treated with dibutyryl cyclic GMP (db‐cGMP) and dibutyryl cyclic AMP (db‐cAMP), respectively, and added methylxanthines and ionophores also increased rosette formation by Xenopus laevis lymphocytes. Added alone, the antagonists used did not affect rosette formation, and the increase induced by db‐cAMP was not blocked by a β adrenoreceptor antagonist.
The stimulation of a and/or β adrenoreceptors resulted in a reduction in rosette formation by cells from all five urodele species, as did the addition of db‐cGMP. However, in samples from four urodele species, db‐cAMP increased rosette formation. Added db‐cAMP reduced rosette formation by lymphocytes from the fifth urodele species tested, i.e. Triturus cristatus carnifex. The results are discussed in terms of the involvement of surface adrenoreceptors and intracellular mechanisms in the regulation of immune responses, and in terms of the evolution of immune capacity within the Amphibia.