Adhesion of erythroid progenitors to FN and its chymotryptic fragments. Bone marrow cells were incubated in wells coated with BSA, FN, CBD, 30-/35-kD, and 42-kD fragments of FN at concentrations supporting maximal adhesion. After 2 hours, the unattached and attached populations were assayed for primitive BFU-E (□), mature BFU-E (▨), and CFU-E (▪). The results are expressed as the mean percent cell adhesion ± SEM (n ≥ 7), * P ≤ .02.