title: Response to Malassezia pachydermatis by peripheral blood mononuclear cells from clinically normal and atopic dogs.
abstract: OBJECTIVE
  To investigate the potential cell-mediated immune response of atopic dogs to the yeast Malassezia pachydermatis and to correlate it with the type-1 hypersensitivity (humoral) response of the same population of dogs.
  
  
  METHODS
  16 clinically normal dogs, 15 atopic dogs with Malassezia dermatitis, 5 atopic dogs with Malassezia otitis, and 7 atopic control (ie, without Malassezia dermatitis or otitis) dogs.
  
  
  METHODS
  A crude extract of M pachydermatis was extracted for use as an intradermal allergy testing reagent and for stimulation of isolated peripheral blood mononuclear cells in vitro. Flow cytometry was also used to assess cell surface antigenic determinants (CD3, CD4, CD8, CD14, CD21, CD45RA, surface immunoglobulin) on peripheral blood mononuclear cells.
  
  
  RESULTS
  Atopic dogs with cytologic evidence of Malassezia dermatitis had an increased lymphocyte blastogenic response to crude M pachydermatis extract, compared with clinically normal dogs and dogs with Malassezia otitis. Atopic control dogs did not differ significantly in their responses from atopic dogs with Malassezia dermatitis or otitis. A significant correlation was not found between the lymphocyte blastogenic response and the type-1 hypersensitivity response to M pachydermatis within any of the groups.
  
  
  CONCLUSIONS
  Cell-mediated and humoral reactivities to M pachydermatis contribute to the pathogenesis of atopic dermatitis in dogs but are not directly correlated. Modification of the dysregulated immune response toward M pachydermatis may assist in the reduction of pathologic changes associated with an atopic dermatitis phenotype in dogs.
authors.affiliation: Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Philadelphia 19104, USA.
authors.forename: Daniel O
authors.initials: DO
authors.lastname: Morris
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Clayton
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Drobatz
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Felsburg
mesh_terms: D000818:Animals; D000917:Antibody Formation / Q000276:immunology; D003876:Dermatitis, Atopic / Q000097:blood / Q000276:immunology / Q000382:microbiology / Q000662:veterinary*; D003881:Dermatomycoses / Q000097:blood / Q000276:immunology / Q000662:veterinary*; D004283:Dog Diseases / Q000097:blood / Q000276:immunology*; D004285:Dogs; D005434:Flow Cytometry; D007111:Immunity, Cellular / Q000276:immunology; D007963:Leukocytes, Mononuclear / Q000276:immunology*; D016131:Lymphocyte Subsets / Q000276:immunology; D008290:Malassezia / Q000276:immunology*; D012882:Skin Tests / Q000662:veterinary; D018709:Statistics, Nonparametric