ABSTRACT
<p><b>OBJECTIVE</b>To study the relation of tumor interstitial T lymphocyte subset activity to the clinical staging of non-small-cell lung cancer (NSCLC) and the immune response.</p><p><b>METHODS</b>Immunohistochemical staining for CD4(+), CD8(+) and CD4(+)CD25(+) Foxp3(+) (regulatory T cells, Treg) T cells was performed on paraffin-embedded tissues from 60 NSCLC cases.</p><p><b>RESULTS</b>Compared to stage I/II NSCLC patients, patients in stage III/IV showed a significant decrease in the percentage of CD4(+) and CD4(+)/CD8(+) T cells (P<0.05) and an increase in CD8(+) and CD4(+)CD25(+) Foxp3(+) T cells (P<0.05). Treg cells were enriched in the tumor tissue as compared with those in the adjacent tissues.</p><p><b>CONCLUSIONS</b>The proportion of CD4(+)CD25(+) Foxp3(+) Treg cells is positively correlated to the clinical staging of NSCLC, in which T cell-mediated immune response is suppressed.</p>