Characterization of Plasminogen Binding to NB4 Promyelocytic Cells Using Monoclonal Antibodies against Receptor-Induced Binding Sites in Cell-Bound Plasminogen

Table 1

Plasminogen binding to cell surfaces of several leukemic cell lines and normal peripheral blood cells.

Cell type	Cell lineage	Molecules of plasminogen bound/cell (×10^6)
NB4	Promyelocytic	38.0±1.8
KG1a	Myeloblastoid	1.5±0.2
K562	Erythromyeloid	3.1±0.2
HL-60	Promyeloid	1.7±0.3
U937	Monocytoid	2.0±0.7
THP-1	Monocytoid	1.6±0.2
Nalm6	Pre-B-Cell	1.2±0.2
Molt4	Undifferentiated T cell	1.1±0.4
Neutrophils		0.35±0.07
Monocytes		0.58±0.08
Lymphocytes		0.59±0.06

Binding analyses were carried out by incubation of washed cells (2–5 × 10⁶/mL) with radiolabeled plasminogen (100 nM) in a total volume of 200 μL for 2 hours a 4^°C. Cells were then separate from the whole reaction mixture by centrifugation of aliquots in 20% sucrose solution. The specific binding of radiolabeled plasminogen was determined by subtracting counts bound in the presence of 0.15 M ε-ACA. Results are the mean ± SD of 2–4 separate experiments.