DIFFERENTIAL MODULATION OF CHICKEN LYMPHOCYTE BLASTOGENESIS AND CYTOTOXIC ACTIVITY OF NATURAL-KILLER-CELLS IN-VITRO BY RETINOL, RETINOIC ACID AND BETA-CAROTENE

The effects of retinol (ROL), retinoic acid (RA) and beta-carotene (CA R) on the response of chicken lymphocyte blastogenesis and on the cyto toxic activity of natural killer (NK) cells were evaluated in vitro. S plenocytes were isolated from healthy growing chicks and cultured in p resence of different concentrations of ROL, RA and CAR under similar e xperimental 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 solut ions. Addition of ROL stock solutions diluted in cell culture medium s uppressed lymphocyte response in a linear dose-dependent manner wherea s pre-dilution of ROL stock solutions in fetal bovine serum (ROL-FBS) increased blastogenesis in a linear manner. Addition of 10 mu M 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 w ere added at a concentration of 10 mu M and 1 mu M, respectively. Howe ver, RA and CAR pre-diluted in FBS (RA-FBS, CAR-FBS) increased prolife rative response of Con A-induced cells in a quadratic dose-dependent m anner. At peak levels of RA-FBS and CAR-FBS, blastogenesis was respect ively 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 red uced when ROL was added to the cultures, whereas RA and CAR enhanced N K 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 beta-carotene ina dose-d ependent manner and by the method used to prepare the working solution s.