853 Profiling of donor-specific immune effector signatures in response to rituximab in a human whole blood loop assay using blood from CLL patients by Martin Höglund, Mattias Mattsson, Erika Fletcher, Linn Dynesius, Justina Jarblad, Martin Lord, Mikaela Zekarias, Xiaojie Yu, Mark Cragg, Caroline Hammarstom, Kerstin Hamberg Levedahl