The inflammatory cell infiltrates in scalp skin of 35 patients, 20 with alopecia areata (AA), 7 with totalis, and 8 with universalis were characterized with the ANAE (alpha-naphthylacetate esterase) marker, monoclonal antibodies, and electron microscopy. As demonstrated by the ANAE staining, no clear difference in the main lymphocyte subclasses (T and B cells) or macrophages was seen between the different types of alopecia or as compared to control patients' scalp skin. However, T lymphocytes and macrophages were seen most frequently and in greater numbers perivascularly and infiltrating the hair bulb in those cases of AA where active hair loss took place. Using monoclonal OKT (OKT-3, -4, and -8) antibodies and the avidin-biotin immunoperoxidase method on frozen sections, a concentration of OKT-8 reactive cells (suppressor/cytotoxic T cells) was seen peribulbarly and invading the hair infundibulum. The cells affecting the hair infundibulum were further studied by electron microscopy. They could be classified into three main types: small lymphocytes (60%), macrophages (30%) and cells closely resembling large granular lymphocytes (LGL) (10%). LGL have previously been considered to be human natural killer (HNK) cells. Thus the hair follicle seems to be the target for the cellular immune response in alopecia. Whether HNK cells participate in the destruction of hair bulbs remains to be investigated.

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Histochemical and immunohistochemical techniques were used to identify T lymphocytes, mononuclear phagocytes and plasma cells in situ from allergic and toxic epicutaneous test reactions. Intracellular alpha-naphthyl acetate esterase (ANAE), endogenous peroxidase and immunoglobulin were used as markers for inflammatory cells. In allergic contact dermatitis 76 +/- 7% of all cells were ANAE-positive T lymphocytes, 13 +/- 6% mononuclear phagocytes and 12 +/- 6% ANAE-negative cells. In toxic skin lesions the corresponding values were 64 +/- 20%, 18 +/- 15% and 18 +/- 6%, respectively. There were no statistically significant differences between the allergic and toxic skin reactions. The basic reaction type in allergic and toxic contact dermatitis seems to be similar, with possibly some qualitative and quantitative differences.

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