HLA-G protein up-regulation in primary cutaneous lymphomas is associated with interleukin-10 expression in large cell T-cell lymphomas and indolent B-cell lymphomas.

Primary cutaneous lymphomas (CLs) constitute a spectrum of diseases characterized by a clonal accumulation of lymphocytes in the skin. Most CLs display a T(h)2 cytokine profile, including expression of interleukin-10 (IL-10). Because the up-regulation of HLA-G, a nonclassical class Ib molecule inducible by IL-10, might account for the immunescape of the malignant clone, HLA-G and IL-10 expression has been investigated in 45 cases of primary CL (10 of B-cell and 35 of T-cell origin) with quantitative polymerase chain reaction (PCR) and immunohistochemistry. HLA-G message was present in all cutaneous B-cell (CBCL) and T-cell (CTCL) lymphomas evaluated. Immunohistochemistry revealed HLA-G protein expression in 23 (51%) of 45 cases (7 of 10 CBCL, 16 of 35 CTCL). While in CBCL mostly indolent types displayed HLA-G positivity, in CTCL HLA-G expression was associated with high-grade histology and advanced stage of the disease. Except for neoplastic and infiltrating lymphocytes, other cells such as macrophages and dendritic cells showed HLA-G immunoreactivity. Furthermore, IL-10 protein expression was demonstrated in 16 (73%) of 22 HLA-G(+) cases, which correlated with HLA-G protein presence (P <.001). HLA-G up-regulation together with IL-10 expression in CL might additionally contribute to the evasion of immunosurveillance and facilitate the transition from low- to high-grade lymphomas.