Characterization of the Mononuclear Infiltrate in Basal Cell Carcinoma: A Predominantly T Cell-mediated Immune Response With Minor Participation of Leu-7+ (Natural Killer) Cells and Leu-14+ (B) Cells

We investigated the peritumoral inflammatory infiltrate in 22 basal cell carcinoma (BCC) from 18 patients using a series of monoclonal antibodies. In all the 22 BCC the infiltrate consisted mainly of T cells (55 ± 15%) and only in three cases an invasion of the tumor nests by these cells was observed. The T helper (TH) subset predominated over the T suppressor/cytotoxic (Ts/c) subset (TH/Ts/c ratio of 1.9 ± 0.8). In 8 of 22 BCC mild infiltrate was observed with 48 ± 13% T cells and a TH/Ts/c ratio of 1.5 ± 0.6. In 14 of 22 BCC moderate to heavy infiltrate with 59 ± 15% T cells and a TH/Ts/c ratio of 2.0 ± 1.0 was observed. There was a significant difference in the percentage of T cells in BCC with moderate to heavy infiltrate and that in BCC with mild infiltration. The mean percentage of HLA-DR+ cells was 54 ± 11%; Langerhans cells (LC) 4 ± 5%; and Leu-M5+ (monocytes and macrophages) 16 ± 11%. Less than 2% Leu-14+(B) cells were seen in the infiltrate. The mean percentage of Leu-7+ (natural killer) cells was 4 ± 4%, and only 1 of 22 BCC Leu-7+ cells invaded tumor nests, contacting with tumor cells. From these results we concluded that T cells play a major role in the defence against BCC proliferation. The main role of Langerhans cells and Leu-M5+ cells may be that of antigen presentation. B cells and NK cells probably play a minor role in the local defence against BCC proliferation.