Foxp3 expressing CD4+ CD25+ and CD8+CD28- T regulatory cells in the peripheral blood of patients with lung cancer and pleural mesothelioma.

The role of T regulatory (Treg) cells in
human cancer has not yet been clarified. We assessed the
presence and function of CD4+ and CD8+ Treg cell
subsets in the peripheral blood of patients with lung
cancer (LC) and pleural mesothelioma (PM). We found a
low but significant increase in the number of CD4+ T
cells with phenotype and functional features of Treg cells
in LC patients compared to normal healthy controls
(NHC). Furthermore, total CD4+ T cells from LC pa-
tients proliferated less than cells from controls, suggesting
that the increase in the CD4+ Treg cell pool has func-
tional importance. LC patients also showed an expansion
of the CD8+CD28- T cell subset and these cells ex-
pressed Foxp3 mRNA, as recently observed in alloanti-
gen-specific CD8+CD28- T suppressor cells. No varia-
tion of peripheral Treg cell subsets was found in patients
with PM, a disease with a predominantly localized nature.
However, the lack of correlation between cancer stage and
the number or the function of peripheral Treg cells in LC
patients refuted the hypothesis that these cells are in-
volved in tumor spreading. A possible involvement of the
peripheral Treg cell pool in cancer development and/or in
inducing systemic immunosuppression in LC patients can
be hypothesized.