HLA Allele Associations and V‐Beta T‐Lymphocyte Expansions inPatients With Psoriasis, Harboring Toxin‐Producing Staphylococcus aureus

HLA alleles have been associated with psoriasis. Toxin-producing strains of Staphylococcus aureus behave as superantigens, and if present in patients, might play a role in the exacerbation of psoriatic lesions by activating certain V-beta (V beta) T-lymphocyte subsets. Allele frequencies in 22 patients and 22 controls (alleles determined by DNA/SSP typing) were used to calculate a relative risk of $4.7$ ($P < .05$) for HLA-Cw6. S aureus was isolated from the throat of 11 patients. Enterotoxins A and C were detected by agglutination in the culture filtrate of one isolate. The enterotoxin A and/or C genes were detected by PCR in 9 isolates, and transcripts were detected by RT-PCR in 7 of them. None of the isolates from controls harbored enterotoxin genes. V beta expansions were detected by RT-PCR in all 22 patients. Low or no V beta expansions were obtained in controls. The association of HLA-Cw6 with psoriasis in Lebanese concurs with that reported for other ethnic groups. Toxin-producing isolates that colonize patients might play a role in the exacerbation of psoriatic lesions.