Differential modulation of chicken lymphocyte blastogenesis and cytotoxic activity of natural killer cells in vitro by retinol, retinoic acid and beta-carotene

Abstract

Summary The effects of retinol (ROL), retinoic acid (RA) and B-carotene (CAR) on the response of chicken lymphocyte blastogenesis and on the cytotoxic activity of natural killer (NK) cells were evaluated in vitro. Speenocytes were isolated from healthy growing chicks and cultured in presence of different concentrations of ROL, RA and CAR under similar experimental conditions. Lymphocyte response to concanavalin A (Con A) was affected by adding ROL, RA and CAR to the cultures, by the time of exposure and by methods used for diluting ROL, RA and CAR stock solutions. Addition of ROL stock solutions diluted in cell culture medium suppressed lymphocyte response in a linear dose-dependent manner whereas pre-dilution of ROL stock solutions in fetal bovine serum (ROL-FBS) increased blastogenesis in a linear manner. Addition of 10 μM of ROL-FBS at the beginning of the incubation period or 16 h after enhanced proliferative responses by 5 and 9 times, respectively, as compared to Con A-induced cells without ROL. Suppressed proliferative response of Con A-induced cells was seen when both RA and CAR working solutions were added at a concentration of 10 μM and 1 μM, respectively. However, RA and CAR pre-diluted in FBS (RA-FBS, CAR-FBS) increased proliferative response of Con A-induced cells in a quadratic dose-dependent manner. At peak levels of RA-FBS and CAR-FBS, blastogenesis was respectively 2.1 and 1.3 times higher than activated cells without RA-FBS or CAR-FBS. No significant increase was detected with RA or CAR directly diluted in RPMi medium. Cytotoxic activity of chicken NK cells was reduced when ROL was added to the cultures, whereas RA and CAR enhanced NK activity. Both preparations of tested compounds had similar effects on NK activity. Our results showed that immunocompetent cell functions were modulated by retinol, retinoic acid and B-carotene in a dose-dependent manner and by the method used to prepare the working solutions.