The invention relates to compounds, compositions comprising the compounds, and methods of using the compounds and compound compositions. A collision-caused data transmission failure and if the number of data transmission failures reaches a predetermined threshold, data is retransmitted by means of an RTSCTS exchange. The ultrasound imaging system further comprises a user input device for inputting and adjusting degrees of freedom parameters. In particular, the present invention relates to 49 novel peptide sequences derived from HLA class II molecules of human tumor cell lines which can be used in vaccine compositions for eliciting anti-tumor immune responses.