Immunophenotyping of the cellular infiltrate in the early elicitation phase of contact dermatitis in the skin of presensitized atopic individuals.

Little is known about the composition of the cellular infiltrate in the early elicitation phase of contact allergy in atopic individuals. Therefore, we rechallenged ten presensitized disease-free atopic volunteers with their known contact allergen and performed biopsies at time 0 and after 6 and 24 h. Ten patients with acute exacerbated atopic dermatitis in the early stage were chosen as a control group. Skin biopsy specimens were processed for immunohistochemistry (APAAP) and evaluated by computer-assisted morphometry. CD4+ and CD45R0+ cells were found to be significantly increased after 6 (t6) and 24 h (t24), and this was accompanied by an enhanced TCR alpha/beta receptor expression at t6-CD45O+ cells showed a marked influx into the epidermis at t24. CD8+ cells infiltrated the basal layer of the epidermis, thus changing the CD4/CD8 ratio from 4.6:1 at t0 to 2.2:1 at t6. CD1a+ epidermal dendritic cells increased significantly from 811 +/- 240/mm2 at t0, to 1210 +/- 333/mm2 at t24 (P < 0.01). At t6 and t24, a so-called 'epitope CD1a+ shedding' was observed into the intercellular spaces of keratinocytes as well as an elongation and enlargement of the dendrites of CD1a+ cells. In the upper dermis, the number of CD1a+ cells increased from 1098 +/- 485/mm2 at t0 to 2388 +/- 740/mm2 at t24 (P < 0.01). In 7/10 volunteers, IgE+ dendritic cells increased significantly in number at t6 (P < 0.02). The activation markers HLA-DR and CD25 were expressed most distinctly at t24. Interestingly, expression of ICAM-1 on keratinocytes occurred only in four of the ten atopic volunteers.(ABSTRACT TRUNCATED AT 250 WORDS)