Microanatomical compartments of clonal and reactive T cells in mycosis fungoides: Molecular demonstration by single cell polymerase chain reaction ofT cell receptor gene rearrangements

Mycosis fungoides (MF) is a cutaneous T cell lymphoma, clinically character ized by patches, plaques and tumors occuring in successive stages of the di sease. In early MF, an infiltrate consisting of mainly reactive T cells is seen in the papillary dermis while tumor cells are mostly confined to the e pidermis. By contrast, later stages show nodular infiltrates formed mostly of tumor cells in the dermis while the epidermis is relatively devoid of tu mor cells; however, knowledge of the localization of clonal T cells has bee n based on histomorphologic features and immunohistochemical stainings visu alizing certain V-beta subfamilies of the T cell receptor (TCR). As these t echniques do not allow for an unequivocal identification of clonal tumor ce lls, we used micromanipulation and single cell PCR amplifying the TCR chain gene rearrangement. A total number of 387 single T cells was isolated from six skin biopsies in five patients in patch, plaque, and tumor stages. Of these, 180 T cells were picked from the epidermis and 207 from the dermal i nfiltrate. The rearranged TCR-gamma DNA could be sequenced from 181 of 387 T cells. In three of six patients representing all three stages, epidermal T cells with a clonal rearrangement could be amplified. In early plaque sta ge a higher degree of epidermal T lymphocytes was found than in initial pat ch, later plaque, and tumor stages with an inverse distribution found for r eactive T lymphocytes, In two patients a biallelic rearrangement was demons trated that had not been detected in prior PCR analysis from blood and skin samples. These data show that clonal (neoplastic) and nonclonal (reactive) T lymphocytes in MF preferentially infiltrate different microanatomical co mpartments of the skin, depending on the stage of disease. The microanatomi cally distinct localization of reactive and clonal T cells suggests that th e absence of direct contact between tumor and host-defense lymphocytes may contribute to tumor persistence and progression in epidermis, peripheral bl ood, and deep dermal tumor cell nests, respectively.