Photomicrographs of morphological changes and aggregation in response to tRA and its inhibition by LFA-1 α and ICAM-2 MoAb. Morphological features of NB-4 cells untreated (A), treated with 100 nmol/L tRA for 24 hours (B), and treated with 100 nmol/L tRA for 72 hours (C). An arrow indicates an eosinophilic perinuclear hof. Aggregation of NB-4 cells treated with tRA for 72 hours (D) and its inhibition by LFA-1 α (E) and ICAM-2 (F ) MoAb are shown.