Heterophils to the Rescue!
They're the Royal Canadian Mounties of the immune systemthe heroes who
show up in the nick of timeand they take on all bacterial invaders, be
they Salmonella, Listeria, Pasteurella, or E. coli. They're
infection-fighting white blood cells called heterophils, and Michael H. Kogut
has found a way to make them do his bidding to protect young poultry. He is a
poultry immunologist in the Agricultural
Research Service Food and Feed Safety
Research Unit at College Station, Texas.
When bacteria invade the intestines and try to pass through the intestinal
wall to the bloodstreamgateway to all the organsheterophils
surround and devour the invaders. The problem: The body's mechanisms that put
heterophils into play typically aren't functional until the host, whether a
child or a chick, is about a week old, allowing plenty of time for bacteria to
gain a toehold. Kogut says the solution is natural substances called cytokines
that are produced by white blood cells.
"We've found a particular type of cytokine called lymphokine that
causes heterophils to come to where the bacteria are and devour them,"
says Kogut. "By giving lymphokines to newly hatched chicks, we're simply
giving the chicks' immune systems a little kickstart."
In tests, Kogut and colleagues have shown that if day-old chicks are given
lymphokines, heterophils are on hand within hours to provide the kind of
protection that a bird's immune system could take a week to develop naturally.
A single dose suffices until the bird's own immune system kicks in.
"We've done experiments with lymphokines taken from older birds that
were immune to salmonella and shown those same lymphokines can protect chicks
against coccidia, the parasites that cause coccidiosis," says Kogut.
"This can apparently protect against anything that's invasive."
Kogut has been working with cytokines since his research days at the
University of Arkansas at Fayetteville. When he joined ARS in May 1992, the
cytokine study came with him. Kogut and Billy M. Hargis of
Texas A&M University's veterinary
pathology department have collaborated on studies showing lymphokine
injections could significantly reduce organ invasion by Salmonella
enteritidis, a type of salmonella found primarily in eggs.
"We've now worked with S. typhimurium, S. gallinarum, and
S. arizoni," Kogut notes. "These are all serologically
distinct bacteria, and the same lymphokines will protect against all of
In hundreds of experiments over 4 years and involving an estimated 5,000
birds, day-old chicks and turkeys have been treated with lymphokines, then
dosed with up to a million disease-causing bacteria per bird. For comparison,
other birds received the bacteria but no protective lymphokines.
"We usually wait 24 hours, then check the birds' organs for signs of
salmonella," Kogut explains. "Eighty percent of the birds that didn't
receive lymphokines have salmonella in their organs, compared with less than 10
percent of the treated birds.
"We've developed a permanent cell line that we can grow in tissue
culture and produce lymphokines in large quantities," says Kogut. "We
have a cooperative research and development agreement with Eli Lilly & Co.
of Indianapolis, Indiana, to develop lymphokine-based protective products for
Unlike other products such as CF-3, a bacterial blend developed at the
College Station lab [See "Natural Microbes Curb Salmonella,"
Agricultural Research, November 1994, pp. 2226.], the
lymphokine-based treatment won't prevent salmonella and other bacteria from
colonizing the bird's intestines. But it will prevent the salmonella from
hitching a ride in the bird's bloodstream to organs such as the ovaries, where
eggs are produced. And it could play a key role in protecting U.S. poultry
health, Kogut adds.
"Salmonella gallinarum is killing 70 to 80 percent of infected
flocks in Mexico," he notes. "Also, there's a type of S.
enteritidis called phage type 4 that is killing hundreds of thousands of
chickens in Europe and China. We've had only small outbreaks of it, but the
potential is here for a big outbreak. A weapon like the lymphokines could help
us go on the offensive against getting it here on a broad scale."
By Sandy Miller Hays.
Kogut is in the USDA-ARS Food and Feed Safety Research Unit, 2881 F&B
Rd., College Station, TX 77835; phone (979) 260-3772.