Cellular immune functions of adults treated with a daily, long-term, low dose of 13-cis retinoic acid

The effects of long-term consumption of 13-cis retinoic acid (13-cRA) on cellular immune functions were measured in young, adult volunteers. The retinoid was administered for 9 months at about 0.13 mg/kg/day. The mean 8AM concentrations of 13-cRA ranged between 30 and 60 ng/ml of serum throughout the study. Corticosteroid levels in plasma decreased significantly throughout treatment, declining from 15.2 ug/dL to 9.1 mg/dL (p < 0.05). T-cell mitogenesis stimulated by PHA or A Con A was not significantly affected, although this parameter was slightly depressed during the first 2 months of treatment. The percentage of B-lymphocytes tended to decrease during treatment and returned to normal after cessation of 13-cRA (p < 0.05), while the percentage of T-cells as measured by E-rosette and by fluorescent antibody tagging of surface antigens did not change. The percentage of non T-cells tended to increase slightly during treatment.