Vimentin and β-tubulin expression in T lymphocytes exposed to different gravity conditions measured by FACS-analysis. Non-activated and Concanavalin A (ConA)/CD28-activated CD4+ T lymphocytes were exposed to altered gravity. A and B. Samples were stained against vimentin and β-tubulin and analyzed by FACS; data are expressed as relative fluorescence intensity (RFI). A: Analysis of non-activated (−) T cells revealed that microgravity (μg)-samples and on-board reference centrifuge (1g)-samples were stained significantly less for vimentin than hardware ground control (H/W)-samples. μg-samples and 1g-samples did not differ significantly in their staining intensities. B: In ConA/CD28 activated (+) T lymphocytes vimentin-staining was not significantly different between 1g and μg samples, but both samples types are stained significantly stronger than baseline (BL)-samples. BL samples were stained significantly less than H/W samples, and H/W samples were stained significantly less than culture control (CC) samples. The medians and individual interquartile ranges are shown. (* p < 0.1, ** p < 0.05, ns = not significantly different, two-tailed Mann–Whitney-U-Test). C and D. Samples were stained against β-tubulin and analyzed by FACS; data are expressed as relative fluorescence intensity (RFI) C: Non-activated (−) T lymphocytes exposed to microgravity (μg) showed a significant increase of β-tubulin in comparison to the cells of the flight hardware on ground (H/W). D: In the analysis of T cell activation ConA/CD28 activated (+) T lymphocytes both the 1g on-board reference centrifuge (1g) and the microgravity (μg) samples had a significantly higher expression of β-tubulin compared with the cells of the baseline (BL) samples. BL and H/W samples had a lower β-tubulin signal than the culture controls.