Resisting infection takes a lot of strength, and sometimes that strength comes at a cost. For example, the growth of newborns exposed to infection can be restricted. But newly hatched chicks aren't completely unprotected from infection; they emerge with antibodies supplied by the mother when she laid the egg. Jennifer Grindstaff, from Oklahoma State University, wondered whether the mother's antibody gift may benefit aspects of a youngster's physiology other than immunity, such as growth? Curious to know whether inherited antibodies could counteract infection and maintain the chick's growth rate,Grindstaff set about recording the growth patterns of 200 chicks after exposure to a fake infection ().
But first Grindstaff needed to find out if specific maternal antibodies would be transmitted through a mother's egg to her chick. Starting off with 32 female quail, Grindstaff exposed 21 of the mums-to-be to fake bacterial and viral infections. Injecting 12 birds with a bacterial cell wall factor(lipopolysaccharide, LPS) and nine with an inactivated avian virus, Grindstaff tested the mothers' immune systems several days later and found that they had all developed antibodies against their fake infections. But had they passed the antibodies on to their eggs? Testing the yolks of fake-infected mum's eggs, Grindstaff was able to identify antibodies to both fake infections. The antibodies had been passed on to the eggs, but would the chicks inherit their mother's resistance?
Grindstaff collected eggs from each of the fake-infected mothers and a group of mothers that had not received fake infections, until she had over 200 eggs ready to hatch in an incubator. Grindstaff admits that the project was a logistical nightmare. `I had spaced all of the eggs out so they wouldn't all hatch on the same day', says Grindstaff, but the chicks conspired against her.`They call to each other in the egg', Grindstaff explains, `and they synchronised, hatching over a 2-day period'. Faced with a population explosion, Grindstaff and her team of undergraduate helpers, Liliana Martinez,Kari Smith and Rosanna Fidler, marked each chick at birth so they knew which family it belonged to. Next the team measured each youngster's vital statistics and collected tiny blood samples to see if the fake-infected mother's antibodies had been passed on. They had, but how would the chicks'immunity, handed down from their mothers, influence their growth if they experienced the same fake infection their mothers had received?
Randomly assigning each of the chicks to one of three groups, Grindstaff immunised the youngsters, by injecting them with one of the fake infections,or injected them with a sterile solution that wouldn't simulate an infection,before monitoring their growth. After a week of franticly measuring the chicks as they grew, Grindstaff realised that the immunised chicks' growth was significantly worse than the chicks that had been injected with the sterile solution. Dealing with the inflammation caused by the fake infections had restricted the chick's growth.
But how had the fake-infected chicks that had received antibodies from their mums grown compared with fake-infected chicks that had not? The results were startlingly clear. Fake-infected chicks that had received maternal antibodies grew much better than fake-infected chicks that had not received maternal antibodies. The mothers' antibodies had apparently protected their offspring, allowing them to deal with the fake infection's inflammation without seriously compromising their growth.
