Traits of Cutaneous Mast Cell Phenotype and Function Associated with Predisposition to Canine Atopic Dermatitis

Health Committee Update
Fall 1998 Newsletter

Robert E. McCaskill, DVM, MPH
Westie Foundation Medical Chairperson

Among the goals of the Westie Foundation of America is to advance the knowledge and understanding of diseases and genetic anomalies affecting the West Highland White Terrier; toward this end, the Foundation will work to identify health concerns and then help fund medical research projects that address these concerns. Though still in its fledgling stages, the Foundation has undertaken to fund, in collaboration with The American Kennel Club's Canine Health Foundation and other breed groups, two multi-year projects, both of which concern long-time health problems associated with the Westie.

The first project with which we became involved is under the direction of Professor Bruce Hammerberg at the College of Veterinary Medicine, North Carolina State University, Raleigh. This study, with the long title of Traits of Cutaneous Mast Cell Phenotype and Function Associated with Predisposition to Canine Atopic Dermatitis proposes to define the differences in the cellular phenotype, activating agonists, and mediator/cytokine release for mast cells obtained from canine atopic dermatitis non-lesional skin compared to mast cells from non-atopic, normal control canine skin. The hypothesis is that atopic dogs have inherited traits of cutaneous mast cell phenotype and function that are different from non-atopic dogs.

The mast cell, which is emitted by the dogs' body as a signal of his being allergic, contains histamine, heparin, and other enzymes. This cell binds to the specific allergen (a protein substance that induces allergy) and then releases these substances into the body's effort to fight the allergen. This release is called degranulation. As the mast cell degranulates, it releases other inflammatory products that cause a variety of other skin changes, including pruritus (itching), edema (swelling), and inflammation. Westies affected with atopic dermatitis itch, likc their feet, and their eyes swell; often, the inside of thier ears turn red, itch, and serve as host to bacteria and yeast infections. In Westies with allergies, the mast cells, which are used to fight foreign proteins, are not working as intended.

Over the planned two-year period of this study, researchers will obtain blood and skin biopsy samples from dogs exhibiting a clinical diagnosis of atopic dermatitis that have been referred to the College's Dermatology Service. Similar samples will be obtained from a similar number of clinically normal, colony-reared dogs. Determination of mast cell phenotype and function will be done by quantitation of surface receptors, endogenous levels of mast cell activation agonists, and response to degranulation agonists.

We now have in hand the initial progress report furnished the Foundation by the researches at the College of Veterinary Medicine at North Carolina State University, and we are pleased to report they have encountered no major barriers in the pursuit of this project to date. The research thus far confirms previous observations made on non-lesion skin from atopic dogs and supports their belief that there are differences, independent of skin disease, between dogs that become atopic and normal dogs. The researchers speculate that mast cells in atopic dogs proliferate in the skin rather than degranulating. This may indicate that mast cells accumulate in great numbers in the skin and later release their inflammatory substances in greater quantities than in a normal dog. Preliminary observations show that atopic dogs demonstrate less mast cell degranulation in response to a protein called the Stem Cell Factor. When this protein is at the place where the mast cell joins the allergen, the mast cell is released. Additionally, they see a higher number of mast cells in non-lesion's skin of atopic dogs when compared to normal dogs.

The success of this study will mean that it will be possible to identify allergic dogs before clinical signs start, to identify Westies prone to allergies from normal Westies at birth, and to breed to eliminate atopic dermatitis. With this success, we then would have Westies that did not itch, or develop skin disease that caused frequent visits to veterinarians and resulted in the dog being abondoned, placed into rescue, or euthanized.

While the NCSU researchers are working hard to determine the cause(s) of atopy, they desperately need more cases for study. If you are aware of a Westie, known or suspected to have atopy, whose owners would permit it tobe a part of this study, please contact Dr. Bob McCaskill at 704-847-4155 for case criteria and other specifics. Participation will involve a visit to the veterinary school in Raleigh, North Carolina. Cost to the participants will be minimal, but the potential reward to our breed of choice is unlimited.

The Foundation has also funded a proposal to develop a DNA-based diagnostic test for carriers of craniomandibular osteopathy to be undertaken at Michigan State University's College of Veterinary Medicine. This study has just gotten underway and is being undertaken with joint support from Cairn, Scottie, and Westie groups.

Your contributions to the Westie Foundation of America have made it possible for the Foundation to support these studies. We will keep you informed of each in future issues of this Newsletter.