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.