Table 4. The specific antibody binding capacity (SABC) for human mammary epithelial cells (HMEC) and L6-hIR cells.

Cell type	Insulin Receptor	IGF-1R	IR:IGF-1R ratio
L6-hIR	204112±22856	N/A	2∶1*
HMEC	1023±168	21313±4279	1∶21

The SABC (average number of antibodies capable of binding to each cell) was measured using either the murine monoclonal antibody 83–7 recognising the human IR or 24–31 recognising the human IGF-1R. Data represent mean (±SD) of at least three independent experiments. No antibody is available that recognises the extracellular domains of the rat IGF-1R, therefore it is not possible to determine the relative number of rat IGF-1R on L6-hIR cells.*unpublished results obtains by Western blot.

IGF-1R, insulin-like growth factor 1 receptor; N/A, not applicable.