PaTu 8988 T cells were observed with an inverted microscope (Zeiss Axio Observer A1, Carl Zeiss Micro Imaging GmbH, Goettingen, Germany) with an attached DHM module that is based on a principle which has been described elsewhere.41 HT-1080 cells were investigated with a recently developed self-interference DHM setup42 which was adapted to the same inverted microscope. For both setups the coherent light source was a frequency-doubled Nd: YAG laser (Compass 315M-100, Coherent, Luebeck, Germany, ). Digital off-axis holograms and self-interference digital holograms of selected adherent and suspended cells were recorded with a charge-coupled device sensor (CCD, , The imaging source DMK 41BF02, Bremen, Germany). For imaging, and microscope lenses (Zeiss LD Acroplan , Zeiss LD Plan-Neofluar, ) were used. All holograms were captured with exposure times below one millisecond to minimize influence of vibrations, movements of suspended cells, and flow of the cell culture medium. The numerical reconstruction of the quantitative DHM phase images from the digital holograms was performed subsequently by spatial phase shifting4,17 in combination with numerical autofocusing.43 All experiments in this study were performed at room temperature and normal atmosphere.