Inverse association between endotoxin exposure and canine atopic dermatitis.

The development of canine atopic dermatitis (CAD) may be related to exposure to mite allergens, bacterial endotoxin and/or fungal glucans. In this study, indoor exposure levels of house dust mite allergens, endotoxins and fungal glucans were measured to determine their possible association with CAD. A case-control study including adult Labrador retrievers with (n=28) and without (controls; n=65) CAD was conducted. Dust samples were collected from the living room floor and the bedding and coat of the dog and these were analyzed for house dust mite allergens Der p1 and Der f1, endotoxin and (1→3)-ß-d-glucan levels. Dog owners were also required to return a questionnaire regarding their home characteristics. The endotoxin exposure level in the coats of dogs was significantly inversely associated with CAD (odds ratio 0.38; 95% confidence interval 0.15-0.97; P<0.05). No significant difference was found in exposure levels to house dust mite allergens and fungal glucans. The results indicated that endotoxin exposure is inversely associated with CAD, suggesting a protective effect of high indoor endotoxin exposure towards the development of the condition.

Functional CD1d and/or NKT cell invariant chain transcript in horse, pig, African elephant and guinea pig, but not in ruminants.

CD1d-restricted invariant natural killer T cells (NKT cells) have been well characterized in humans and mice, but it is unknown whether they are present in other species. Here we describe the invariant TCR alpha chain and the full length CD1d transcript of pig and horse. Molecular modeling predicts that porcine (po) invariant TCR alpha chain/poCD1d/alpha-GalCer and equine (eq) invariant TCR alpha chain/eqCD1d/alpha-GalCer form complexes that are highly homologous to the human complex. Since a prerequisite for the presence of NKT cells is the expression of CD1d protein, we performed searches for CD1D genes and CD1d transcripts in multiple species. Previously, cattle and guinea pig have been suggested to lack CD1D genes. The CD1D genes of European taurine cattle (Bos taurus) are known to be pseudogenes because of disrupting mutations in the start codon and in the donor splice site of the first intron. Here we show that the same mutations are found in six other ruminants: African buffalo, sheep, bushbuck, bongo, N'Dama cattle, and roe deer. In contrast, intact CD1d transcripts were found in guinea pig, African elephant, horse, rabbit, and pig. Despite the discovery of a highly homologous NKT/CD1d system in pig and horse, our data suggest that functional CD1D and CD1d-restricted NKT cells are not universally present in mammals.

Two canine CD1a proteins are differentially expressed in skin.

Lipid antigens are presented to T cells by the CD1 family of proteins. In this study, we characterize the complete dog (Canis familiaris) CD1 locus, which is located on chromosome 38. The canine locus contains eight CD1A genes (canCD1A), of which five are pseudogenes, one canCD1B, one canCD1C, one canCD1D, and one canCD1E gene. In vivo expression of canine CD1 proteins was shown for canCD1a6, canCD1a8, and canCD1b, using a panel of anti-CD1 monoclonal antibodies (mAbs). CanCD1a6 and canCD1a8 are recognized by two distinct mAbs. Furthermore, we show differential transcription of the three canCD1A genes in canine tissues. In canine skin, the transcription level of canCD1A8 was higher than that of canCD1A6, and no transcription of canCD1A2 was detected. Based on protein modeling and protein sequence alignment, we predict that both canine CD1a proteins can bind different glycolipids in their groove. Besides differences in ectodomain structure, we observed the unique presence of three types of cytoplasmic tails encoded by canCD1A genes. cDNA sequencing and expressed sequence tag sequences confirmed the existence of a short, human CD1a-like cytoplasmic tail of four amino acids, of an intermediate length form of 15 amino acids, and of a long form of 31 amino acids.