IMMUNOPHENOTYPING OF THE CELLULAR INFILTRATE IN THE EARLY ELICITATIONPHASE OF CONTACT-DERMATITIS IN THE SKIN OF PRESENSITIZED ATOPIC INDIVIDUALS

Litte is known about the composition of the cellular infiltrate in the early elicitation phase of contact allergy in atopic individuals. The refore, we rechallenged ten presensitized disease-free atopic voluntee rs with their known contact allergen and performed biopsies at time 0 and after 6 and 24 h. Ten patients with acute exacerbated atopic derma titis in the early stage were chosen as a control group. Skin biopsy s pecimens were processed for immunohistochemistry (APAAP) and evaluated by computer-assisted morphometry. CD4(+) and CD45R0(+) cells were fou nd to be significantly increased after 6 (t(6)) and 24 h (t(24)), and this was accompanied by an enhanced TCR alpha/beta receptor expression at t(6)-CD450(+) cells showed a marked influx into the epidermis at t (24). CD8(+) cells infiltrated the basal layer of the epidermis, thus changing the CD4/CD8 ratio from 4.6:1 at t(0) to 2.2:1 at t(6). CD1a() epidermal dendritic cells increased significantly from 811 +/- 240/m m(2) at t(0), to 1210 +/- 333/mm(2) at t(24) (P < 0.01). At t(6) and t (24), a so-called 'epitope CD1a(+) shedding' was observed into the int ercellular spaces of keratinocytes as well as an elongation and enlarg ement of the dendrites of CD1a(+) cells. In the upper dermis, the numb er of CD1a(+) cells increased from 1098 + 485/mm(2) at to to 2388 +/- 740/mm(2) at t(24) (P < 0.01). In 7/10 volunteers, IgE(+) dendritic ce lls increased significantly in number at t(6) (P < 0.02). The activati on markers HLA-DR and CD25 were expressed most distinctly at t(24). In terestingly, expression of ICAM-1 on keratinocytes occurred only in fo ur of the ten atopic volunteers. In general, the early elicitation pha se of allergic contact dermatitis in atopy is characterized mostly by the same events as seen in nonatopics; however, the lower expression o f ICAM-1 on keratinocytes and the increase in IgE-bearing dendritic ce lls seem to be characteristic for atopic individuals with contact alle rgy in the early phase after rechallenge with a contact allergen.