The changes in T-cell morphology during immunological synapse (IS) formation are essential for T-cell activation. Previous researches have shown that T cell changed from spherical to elongated and/or flattened during in contact with B cell. As most powerful antigen presenting cell, dendritic cell (DC) has a strong ability to activate T cells. However, the morphological change of T cell which contacts DC and the relationship between morphological change and T-cell activation are not very clear. Thus, we studied the morphological change of CD4+ T cell during contact with DC. Using live-cell imaging, we discovered diversity in the T-cell morphological changes during contact with DCs. The elongation-flattening of CD4+ T cells correlated with a low-level Ca2+ response and a loss of T-cell receptor (TCR) signalling molecules in the IS, including zeta-chain associated protein kinase 70 (ZAP-70), phospholipase C-γ (PLC-γ) and protein kinase C-θ (PKC-θ), whereas rounding-flattening correlated with sufficient CD4+ T-cell activation. Different morphological changes were correlated with the different amount of accumulated filamentous actin (F-actin) in the IS. Disruption of F-actin by cytochalasin D impaired the morphological change and the localisation of calcium microdomains in the IS and decreased the calcium response in CD4+ T cells. Our study discovered the diversity in morphological change of T cells during contacted with DCs. During this process, the different morphological changes of T cells modulate T-cell activation by the different amount of F-actin accumulation in the IS, which controls the distribution of calcium microdomains to affect T-cell activation.

Increased CD4+CD25+Foxp3+ regulatory T cells (Tregs) predict poor prognosis in renal cell carcinoma (RCC). The aim of this study was to investigate the underlying causes of the aberrant accumulation of Tregs in RCC. pcDNA3.1-hCOX-2 and control pcDNA3.1 were transfected into the RCC cell line OS-RC-2. Under stimulation of anti-CD3/CD28 antibody and APC cells, isolated CD4+Foxp3- T cells were co-cultured with transfected OS-RC-2 culture medium supernatants and different control supernatants, respectively, and 96 h later, the proportion of Tregs in each group was detected using FACS. The suppressive ability of naturally isolated Tregs and transformed Tregs was also analyzed using [3H]-thymidine methods. The results showed that overexpression of COX-2 in OS-RC-2 cells led to higher expression of prostaglandin E2 (PGE2) in the culture medium supernatants. In addition, there was an apparent incremental increase in the percentage of Tregs in the CD4+Foxp3- T cells cultured with the COX-2-overexpressing OS-RC-2 culture medium supernatants. Furthermore, transformed Tregs had the same suppressive ability as naturally isolated Tregs. In summary, transfected RCC cell line culture medium supernatants were capable of converting CD4+Foxp3- T cells to Tregs by producing high levels of PGE2, while COX-2 inhibitors reduced the proportion of transformed Tregs in a dose-dependent manner. Thus, COX-2 inhibitors may induce a local anti-tumor effect and, in turn, may contribute to the eradication of RCC by decreasing transformed Tregs.