Murine T cells exchange cytosol with tumor cells and reveal signs of activation.

<div><p>(A)2x10⁶ splenocytes incubated with 2x10⁶ CMFDA-labeled BM185 cells for 4 h and analyzed for fluorescence uptake by T cells. Likewise to the human PBMCs the mouse model revealed green-fluorescent CD4⁺ and CD8⁺ T cells. In addition, a well detectable green-fluorescent population extending the T cell population could be observed within the splenocytes.</p> <p>(B)Staining of splenocytes with CD3 and CD19 after exposure to tumor cells identified the non-T cell population capable for cytosol uptake as B cells. </p> <p>(C)Summary of four independent incubation experiments of splenocytes with cells of different cell lines. BNL cells are not tumor derived whereas the other lines are tumor cells. </p> <p>(D)Analysis of MHC II expression of the respective cell lines BM185, KLN-205 and BNL CL.2. The level of expression did not correlate with the outcome of cytosol transfer.</p> <p>(E)In contrast to unaffected CD4⁺ T cells (CMFDA^-), CD4⁺ T cells revealing an uptake of tumor derived cytosol (CMFDA⁺) showed signs of activation according to increased expression of CD25 and early activation marker CD69 whereas CD62L slightly decreased. Cells were incubated as described above (A) with subsequent staining of CD4 T cells and activation markers. The pattern of activation was different to the stimulation with 2µg/ml ConA. </p> <p>(F)Proliferation analysis of 1x10⁴ purified T cells revealing CMFDA uptake after 4 h exposure of splenocytes to labeled BM185 cells. For control purified CD4⁺ T cells of naive mice were cultured in medium as it was performed with sorted T cells for 4 days and additional 16 h with ³H thymidine before szintilization. </p> <p>Results are shown as representative scatter-grams or summarizing at least 3 independent experiments as mean ± SEM.</p>