Human beings are not alone in having invented vaccination (疫苗), while bees have done that earlier and they can experience what look like human beings' vaccination programs, which has been confirmed by Gyan Harwood of the University of Illinois, Urbana-Champaign.
Queen bees vaccinate their eggs before they are laid. But the question is how the queen bee receives her antigen (抗原) supply, for she lives purely on royal jelly, a substance produced by nurse bees when they are feeding the young. Dr. Harwood wondered if the nurse bees combined the royal jelly they produced with pieces from pathogens ( 病 原 体 ) they had consumed while eating something brought in from outside.
To test this idea, they collected about 150 nurse bees and divided them into six queenless mini hives equipped with the young to look after. They fed the nurse bees on sugar water, and for three of the hives they added Paenibacillus larvae (类芽孢杆菌幼体), a bacterium causing a disease, to sugar water.
Dr. Harwood and Dr. Salmela labeled the bacteria with a certain dye to make them easy to track. And, sure enough, the microscope confirmed that Paenibacillus larvae were getting into royal jelly produced by those bees which had been fed with the sugar water. Moreover, the examination of this royal jelly revealed higher levels of defensive substance, compared with royal jelly from bees that had not been mixed with Paenibacillus larvae. This substance is thought to help bees' immune systems fight against bacterial infections.
These findings suggest that nurse bees are indeed, via their royal jelly, passing antigens on to the queen, then into eggs. They also mean, because the young receive royal jelly for the first few days after they hatch, the nurse bees are giving the young the second antigens. Each young bee is therefore being vaccinated twice.
