ATRA induces ABCA1 expression in human primary CD4+ T cells. A) Human CD4+ T cells isolated from healthy donors were primed with anti-CD3 and anti-CD28 antibodies and treated with DMSO or 1 μM of ATRA for 3 days. RNA isolation, reverse transcription, and real time PCR were done as described in Methods. ABCA1 RNA expression was normalized to GAPDH RNA expression, and relative RNA fold changes compared to that from DMSO treatment were plotted. B) ABCA1 proteins were detected by Western blot with antibody specific to human ABCA1 as described. GAPDH was used as a loading control. C) ABCA1 RNA expression in response to treatment with different concentrations of ATRA. D) ABCA1 RNA expression in response to treatment with ATRA for various lengths of times. E) CD4+ T cells were activated with anti-CD3 and anti-CD28 antibody or PMA and PHA and were also treated with either DMSO or ATRA. ABCA1 RNA level was analyzed by real-time PCR. F) Anti-CD3/CD28 antibody primed CD4+ T cells were treated with DMSO or 10 μM of U0126 for 2 hours and then treated with or without ATRA. ABCA1 RNA level was quantitated by real-time PCR. Results are representative of three experiments with cells from three different donors.