Effect of β1 subunit antibody and R1-2 monoclonal antibody on adhesion of erythroid progenitors to 30-/35-kD heparin binding fragments of FN. (A) Bone marrow cells were incubated in wells coated with untreated (□, ▧) or heparin-treated (▨, ▪) 30-/35-kD fragments in the absence (□, ▨) or presence (▧, ▪) of β1 subunit antibody. A total of 100 μg/mL of β1 subunit antibody was used for BFU-E assays, while 200 μg/mL was used for CFU-E assays. Unattached and attached population of cells were then assayed for erythroid progenitors. The level of adhesion in the presence of nonimmune IgG was identical to the adhesion observed in the absence of antibody. (B) Bone marrow cells were incubated in wells coated with 30/35-kD fragments in the absence (□) or presence (▪) of R1-2 hybridoma conditioned medium. A 0.5× concentration of R1-2 medium was used for BFU-E assays, while a 4× concentration was used for CFU-E assays. Unattached and attached populations of cells were then assayed for erythroid progenitors. Adhesion in the presence of concentrated control medium was identical to adhesion in either IMDM or in the presence of nonimmune IgG. The results are expressed as the mean percent cell adhesion ± SEM (n ≥ 2), * P ≤ .05.
