Indeed , the adaptive immune system as a whole evolved in an ancestor of all jawed vertebrate .
B and T lymphocytes bearing immunoglobulins and T cell receptors , respectively , are found in all jawed fishes .
The adaptive immune system as a whole evolved in an ancestor of all jawed vertebrate .
B and T lymphocytes bearing immunoglobulins and T cell receptors , respectively , are found in all jawed fishes .