Fr. Weller et al., HLA-DR EXPRESSION IS INDUCED ON KERATINOCYTES IN DELAYED-HYPERSENSITIVITY BUT NOT IN ALLERGEN-INDUCED LATE-PHASE REACTIONS, Clinical and experimental allergy, 25(3), 1995, pp. 252-259
In view of increasing evidence suggesting an active immunoregulatory r
ole of the skin keratinocytes and the observation that the differentia
tion of allergen specific T lymphocytes is critical in the development
of allergy, we evaluated epidermal expression of HLA-DR antigen in sk
in reactions induced with an atopen (house dust mite) and with an non-
atopic antigen (Hemocyanin). Two groups of patients with house dust mi
te (Dermatophagoides pteronyssinus [Der p]) allergy were compared, one
group was skin tested with Der p, the other group was immunized and s
ubsequently skin tested with Helix pomatia Hemocyanin (HPH). Biopsy sp
ecimens taken at 48 h after the HPH (n = 11) and Der p (n = 11) tests
were analysed immunohistologically. Reactions in both groups were comp
arable in size. Immunohistological analysis showed domination by CD4lymphocytes. Expression of HLA-DR antigen by epidermal keratinocytes w
as observed in six out of 11 of the HPH induced reactions, but in none
of the Der p induced reactions. Eosinophils were spotted only through
out the Der p induced reactions, showing a good correlation with the n
umber of CD4 positive lymphocytes. The lack of HLA-DR expression by ke
ratinocytes during the allergen-induced reaction, compared with the He
mocyanin induced reaction can be the result of a difference in cytokin
e profile of the lymphocytes dominating the dermal in filtrate. On the
other hand evidence exists that defective HLA-DR expression by kerati
nocytes enhances antigen induced lymphocyte activation, and may thus c
ontribute to the development of allergen-specific T-lymphocytes.