The Functional Characterization of Interleukin-l0 Receptor Expression on Human Natural Killer Cells

Human natural killer INK) cells are large granular lymphocytes that constitutively express functional forms of the interleukin-2 receptor (IL-2R) and lyse tumor and virally infected cells without prior sensitization. NK cells with high density expression of CD56 (CD56b'ieh') express the high affinity IL-2R and proliferate in response to low (picomolar) concentrations of IL-2. CD56d'm NK cells express the intermediate affinity IL-2R and demonstrate enhanced cytotoxic activity without proliferation in response to high (nanomolar) concentrations of IL-2. In the present study, we characterized IL-1OR expression on human NK cells and the functional consequences of IL-10 binding directly t o highly purified subsets of CD56b"ght and CD56dim NK cells. Binding studies using lZ5lIL-10 indicated that resting human NK cells constitutively express the IL-10 receptor protein at a surface density of approximately 90 receptor sites per cell, with a kd of -1 nmol/L. Alone, IL-10 did not induce proliferation of CD56b'igh' or CD56dim NK cell subsets. However, at low concentrations (0.5 to 5 ng/mL), IL-10 significantly augmented IL-2-induced