Fig. 1.

A representative binding isotherm (a) and binding competition curve (b) for insulin on lymphocytes from Lewis rats 7 d after receiving (Lewis × Brown Norway) F₁ skin allografts. The half maximal equilibrium constant, calculated from the concentration of insulin at which binding is half-maximal, was 1.3 nM. The affinity of unlabelled insulin for its binding site is estimated from the concentration dependence of the binding inhibition curve²⁰ and was 0.2 nM. Both values permit binding at physiological concentrations of insulin.