Camels have "an amazing immune system, unique among mammalians," said scientists Sabah Jassim and Mazen Naji at the Zayed Complex for Herbal Research and Traditional Medicine at Abu Dhabi in the United Arab Emirates. The desert animals are extremely resistant to many deadly viral and microbial contagions, such as tetanus, hoof-and-mouth disease and mad cow disease.

Camel antibodies, as it turns out, are smaller than any other mammalian antibody known, around two-thirds to one-tenth the size of common human antibodies. This means they can enter tissues and cells other antibodies cannot, the researchers explain in the latest issue of the British Institute of Biology's journal The Biologist.

Antibodies act as red flags for the immune system by recognizing foreign invaders and triggering counterattacks against them. Camel antibodies consist of only simple chains of heavy proteins, missing the additional lighter protein chains that other species' more complicated antibodies use to help bind to intruders.

Nevertheless, as simple as they are, camel antibodies remain very effective. In fact, camel antibodies demonstrate the remarkable ability to render germ molecules inactive, reaching inside enemy enzymes and latching onto the active portions of the toxins use to raid cells -- preventing them from working.

"This is the first antibody structure that has been observed to penetrate an enzyme active site," Jassim and Naji noted.

The large number of antiviral antibodies found in camel milk and blood serum shows that they have been exposed to disease but not infected, further proof that camel antibodies have the power to neutralize viral enzymes. "Viral enzymes play a key role in triggering a disease. If viral enzymes could be neutralized, viral replication could not take place," the scientists said.

Because camel antibodies have fewer components than other antibodies, the researchers say they may prove easier to manufacture, presenting "advantages over common antibodies in the design, production and application of clinically valuable compounds."

Antibody researcher Serge Muyldermans at the Free University of Brussels said a steadily growing group of scientists are combining to investigate multiple aspects of these extraordinary antibodies.

"The research is going quite fast," Muyldermans said in an interview with United Press International. "The largest challenge will be in persuading scientists and medical practicioners of the low immunogenic risks of these antibody fragments."

Muyldermans added that camel antibodies may prove important in cancer therapy. When doctors want to treat cancer, they want a targeting method that can penetrate tumors and label cancer cells while leaving healthy tissue unmarked. Simple, small cancer antibodies may prove to be these critical red flags.

"The search for new drugs is becoming critical because of the emergence of drug-resistant microorganisms," Jassim and Naji said. "Camelid antibodies provide a possible route to eradicate pathogens and prevent immunosuppression diseases."

(Reported by Charles Choi in New York.)