Expression of Master Regulators of Helper T-Cell Differentiation in Peripheral T-Cell Lymphoma, Not Otherwise Specified by Immunohistochemical Analysis.

Peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS) comprises nodal and extranodal mature T-cell lymphomas, which do not correspond to any of the specifically defined entities of mature T-cell lymphoma in the current classification.

During T-cell maturation, naïve T-cells include two distinct cell types, CD4-positive helper T-cells (Th) and CD8-positive cytotoxic T-cells. Following antigen stimulation, naïve Th cells differentiate into several subtypes of effector Th cells, including helper T-cells type1 (Th1), helper T-cells type 2 (Th2), follicular helper T-cells (TFH), regulatory T-cells (Treg), IL-17 producing T-cells (Th17), central memory T-cells (TCM), and effector memory T-cells (TEM).

Previously, these subtypes of effector Th cells have been classified according to their pattern of cytokine secretion and expression of surface antigens, including chemokine receptors. More recent immunological researches have identified several transcription factors responsible for T-cell differentiation. The master regulators associated with Th, Th1, Th2, Th17, and Treg differentiation are reported to be Th-POK, T-Bet, GATA3, RORγt, and FOXP3, respectively.

The origin of the neoplastic cells of PTCL-NOS is thought to be effector Th cells because the tumor cells usually express specific surface antigens such as pan-T-cell markers (CD2 and CD3), an effector T-cell marker (CD45RO), and a Th marker (CD4). However, the normal cellular derivation of PTCL-NOS remains unclear because the immunophenotypic profiles of PTCL-NOS are heterogeneous and not entirely disease specific.

To presume the normal counterparts of PTCL-NOS, we used immunohistochemical analysis to examine the expression of the master regulators of T-cell differentiation and surface antigens, including chemokine receptors associated with the subtypes of Th cells.

The study population included ten Japanese patients who were diagnosed histopathologically with PTCL-NOS at the hospital of Kyoto Prefectural University of Medicine from 1993 to 2008. There were six male and four female patients who ranged in age from 26 to 78 years (mean 56 years) at diagnosis.

Immunohistochemical staining was applied to 4-μm-thick paraffin-embedded sections of diagnostic lymph node, skin or liver tumor biopsy specimens. Sections were stained using a standard indirect avidin-biotin horseradish peroxidase method and diaminobenzidine (DAB) color development. Cases were considered positive if 25% or more of the tumor cells were stained with an antibody. For negative and positive staining controls, we used paraffin-embedded tissue sections of tonsillitis, nonspecific lymphadenitis, AILT, follicular lymphoma and diffuse large B-cell lymphoma.

First, we examined the expression of the master regulator of helper T-cells (Th-POK) and the marker of effector T-cells (CD45RO), and all cases were positive for both.

Next, we examined the expression of the master regulators of differentiation to subpopulations within Th cells (Th1, Th2, Treg and Th17). Three cases each were positive for T-Bet, and GATA3, but none of the cases showed FOXP3 or RORγt.

Among the four cases not expressing these master regulators, two cases were positive for the surface antigens of central memory (TCM) (CCR7 and CD62L), and one case was positive for follicular helper T-cell (TFH) phenotype (BCL6, CXCL13 and PD-1). The remaining case was negative for all markers of effector Th subtypes.

All ten PTCL-NOS cases exhibited CD45RO and Th-POK, which characterized effector helper T-cells. Furthermore, the lymphoma cells of nine of the ten cases exhibited the expression of master regulators or surface antigens which characterized Th1, Th2, TCM and TFH.

No relevant conflicts of interest to declare.