Differential human interferon alpha receptor expression on proliferating and non-proliferating cells

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Abstract
The expression of interferon-.alpha.(IFN-.alpha.) receptors was studied on a variety of human cells, using monoiodinated IFN-.alpha.2 probes. Steady-state binding at 4.degree. C revealed a single class of non-interacting IFN receptor on peripheral blood lymphocytes, and tonsillar B lymphocytes, which are both known to be G0/G1 resting cell populations. The binding affinity of this class of receptor was found to be on the order of 5 .times. 10 10-10 M, expressed as an apparent dissociation constant (Kd). However, cells proliferating either in culture or in vivo were found to express a heterogeneity in IFN-.alpha.2 binding. Such binding could be objectively resolved (by a version of the LIGAND program of P. Munson) into a two-site receptor model. Hill plots of binding to proliferating cells indicated a negative cooperativity in the interaction of IFN and receptor. The high-affinity component, expressed on proliferating cells, typically exhibits a Kd of (1-10) .times. 10-11 M, while the lower-affinity component indicates a Kd of (1-10) .times. 10-9 M. Furthermore, the low-affinity component is apparently expressed on the order of 10-200 times the copy number, per cell, of the high-affinity site. Affinity-labeling experiments revealed that, in addition to the 140-160-kDa IFN-binding complex reported by others, both the proliferating and non-proliferating cell populations possess a novel IFN-binding component of 60 kDa.