P991: IMPAIRMENT OF TCR SIGNALLING IN PATIENTS WITH MYELOFIBROSIS TREATED WITH RUXOLITINIB - P. Harrington; R. Dillon; D. Radia; D. McLornan; N. Curto-Garcia; C. Woodley; S. Asirvatham; S. Kordasti; C. Harrison; H. de Lavallade (HemaSphere, 2022)