Ia+ epithelial dendritic cells during oral carcinogenesis in the rat

Physiology and pathophysiology of dendritic cells

Dendritic cells are antigen-presenting cells derived from the hematopoietic stem cell. The dendritic cell family includes Langerhans' cells (CD1a-positive dendritic cells of the skin), and antigen-presenting cells that are found in the lymphoreticular system and throughout the organ parenchyme. Dendritic cells play a key role in both the primary and secondary immune responses. Several studies indicate that these cells participate in antitumor immunity, tumor surveillance, graft-versus-host disease, and in the pathogenesis of clinical syndromes of unknown origin or those induced by viruses, such as the human immunodeficiency virus. Different disorders are characterized by an abnormal proliferation and accumulation of dendritic cells; for example, the Langerhans' histiocytes, which accumulate in Langerhans' cell histiocytosis. In this review the immunophenotypic, morphological, and functional characteristics of the dendritic cell family is described. The clinical and laboratory studies suggesting a unique role for these cells in various syndromes and diseases are reviewed. The Langerhans' cell histiocytoses and the malignant disorders associated with transformation of cells belonging to the dendritic cell family, are discussed.

Inflammatory cell infiltrate associated with primary and transplanted tumours in an inbred model of oral carcinogenesis

This study characterised the nature of the local cellular immune responses associated with an inbred animal model of oral carcinogenesis. Inbred F344 rats developed moderately- to well-differentiated primary oral squamous cell carcinomas (SCC) after treatment with the carcinogen 4-nitroquinoline N-oxide (4-NQO) in vivo for 5-6 months. The inflammatory cell infiltrate associated with the primary tumours was predominantly of the macrophage lineage (CD45+, Ia+) and contained smaller numbers of CD8+ cells (NK cells, cytotoxic/suppressor T cells), CD5+ cells (T cells) and CD25+ cells (activated cells; T and NK cells). Keratinocyte cell lines were established from three lingual and one palatal SCC. By contrast to normal keratinocytes, tumour-derived cell lines were immortal and independent of 3T3 fibroblast support. All of the tumour-derived cell lines were tumorigenic in athymic (nu/nu) mice and showed contrasting latent periods of tumour development and histological differentiation; normal keratinocyte grafts were non-tumorigenic in athymic mice. Three of four malignant cell lines formed well-differentiated tumours in syngeneic F344 rats; the tumours regressed after 10-14 days. Regressing grafts contained significantly larger numbers of NK cells (CD5-, CD8+) in the inflammatory cell infiltrate compared with that associated with primary tumours (p < 0.04). One malignant cell line and normal keratinocytes were non-tumorigenic in syngeneic hosts. The results demonstrate phenotypic variation in the cell-mediated immune responses associated with the actively growing primary SCC and the regressing tumours in syngeneic hosts and suggest that NK cells, possibly activated by local T cell responses, are important for tumour rejection in this model.

Epithelial dendritic cells in pathological human oral tissues

Epithelial dendritic cells (EDC) were examined in human oral tissues with non-specific keratosis, lichen planus and squamous cell carcinoma. Acetone-fixed frozen sections were stained using an indirect immunoperoxidase technique and monoclonal antibodies to the human CD1 thymocyte (OKT6) and HLA-DR antigens. Significantly more T6+ and DR+ EDC were present in lichen planus tissues than normal controls, tissues with non-specific keratosis and the epithelial overlying/adjacent to squamous cell carcinomas, the latter tissues having comparable numbers of both T6+ and DR+ EDC. By contrast, significantly fewer T6+ EDC and significantly more DR+ cells were present in the invasive epithelium of squamous cell carcinomas than the overlying/adjacent epithelium of carcinomas, the non-specific keratosis group and the normal tissues. 23-60% of pathological tissues had either focal or general DR+ reactivity in keratinocytes, but there was no correlation between the density of T6+ or DR+ EDC and the keratinocyte DR status of the tissues. The results suggest that immunological enhancement occurs in lichen planus and possibly immunological impairment may characterize invasive squamous cell carcinoma.