Apolipoprotein E restricts interleukin-dependent T lymphocyte proliferation at the G1A/G1B boundary.

Apolipoprotein E (apoE), a lipid transport protein important in cholesterol homeostasis, inhibits the proliferation of interleukin-dependent lymphocytes. Growth factor-responsive cells are blocked in the G1A phase of the cell cycle. Suppression by apoE is independent of growth factor, as evidenced by the fact that interleukin-2 (IL2)- and IL4-dependent proliferation of HT-2 T lymphocytes is equally inhibited. apoE has no effect on IL2-augmented killing of target cells by cytotoxic T cells, indicating that it has no direct effect on signaling via interleukin receptors. The data are consistent with inhibition by apoE of an event or pathway distal to receptor signaling and required for G1A transition, or G1B entry.