In situ characterization of cellular infiltrates in lupus vulgaris indicates lesional T-cell activation.

Skin biopsy specimens from nine patients with lupus vulgaris were examined in situ by means of monoclonal antibodies directed against phenotypes of lymphocyte subsets, Langerhans cells, HLA-DR antigens, and interleukin 2 receptor. The epidermis showed prominent changes, including intense expression of HLA-DR on keratinocytes, increase in epidermal cell layers, moderate to high Langerhans cell hyperplasia, and infiltration by CD3+ pan-T cells as well as CD8+ (cytotoxic/suppressor) and CD4+ (helper/inducer) T cells. The predominant lymphocyte in the dermal granulomas was the activated CD3+ T cell, expressing major histocompatibility complex class II antigens and interleukin 2 receptor. CD4+ and CD8+ cells were randomly distributed among the epithelioid cells, which showed intense staining for major histocompatibility complex class II antigens. In all except two patients, the CD4+ population was greater than that of the CD8+ cells. CD1+ Langerhans cells were scattered in moderate numbers in the dermal granulomas. Acid-fast bacilli were conspicuously absent in the biopsy specimens. These features suggest that T-cell activation and Langerhans cell hyperplasia are prominent features of dermal tuberculosis.