Immunophenotype analysis of dendritic cells and lymphocytes associated with cutaneous malignant melanomas.

ABSTRACT

The purpose of this study was to investigate the relationship between changes in density and distribution of dendritic cells, both in epidermis and in peritumoral infiltrate, and lymphocyte subset variations in malignant melanomas (MM) of patients belonging to different risk groups. The collective immunoreactive expression of six markers (S100 protein, CD1-a, HLA-DR, CD4, CD8 and CD25) was analyzed in 13 cutaneous malignant melanomas. Changes were observed in density and distribution of Langerhans cells (LC) (S100+, CD1-a+) in the epidermis overlying the tumor, as well as in peritumoral and intratumoral locations, independently of the tumor-invasion level. A decrease was recorded in LC (S100+, CD1-a+) in the epidermis overlying six tumors, whereas most of the MM studied showed an increase of LC (S100+, CD1-a+) in peritumoral infiltrate. The expression of HLA-DR in tumor cells was controversial; it was observed in three moderate-risk MM, but it was negative in high-risk tumors. The percentage of CD4+ cells was in most cases greater than that of CD8+ in the peritumoral infiltrate, irrespective of the degree of histopathological malignancy. The concomitant expression of the lymphocytic activation marker CD25 (receptor for interleukin 2) in lymphocytic infiltrate was variable. Peritumoral infiltrate in three high risk MM contained few CD25+ cells, and a concomitant decrease was recorded in LC. This preliminary report shows that alterations in the density and distribution of LC may be responsible for determining the degree or T lymphocyte activation, and this may be critical for the development of effective tumor-directed immunity. Further studies are required to demonstrate these hypothetical interrelations.