Lymphocytes and Langerhans cells in allergic patch tests.

An immuno-histochemical study of immuno-competent cells in the skin during fully developed 3-7 d patch tests was performed. Most inflammatory cells were OKT 11 positive T-lymphocytes. The majority of these cells were of the helper/inducer phenotype (OKT 4+), but in the later stages a relative increase of OKT 8+ cells was seen in 5 specimens out of 20. A focal decrease of OKT 6+ Langerhans cells was observed in the epidermis, while their number increased considerably in the dermis. Also observed was an inflammatory reaction of hair follicles with moderate numbers of OKT 6+ cells in the peribulbar infiltrate. This indicates that hair follicles may possibly act as shunt pathways for allergens.