RESUMO
The thymic microenvironment plays a central role in T-cell differentiation. Involution of the thymus begins relatively early in life, resulting in decreased immunity. Nigella sativa is known for its immunopotentiating effects. The aim of the study was to elucidate the effect of N. sativa on the structure of the thymus in young and mature adult rats. Twenty-eight male Wistar albino rats were divided into two groups: group I and group II. Group I was further divided into subgroup Ia and subgroup Ib. Subgroup Ia included seven 1-month-old young rats weighing 50-60 g that received plain water by gavage for 15 days. Subgroup Ib included seven young rats that received 2 ml/kg body weight of 1% petroleum ether extract of N. sativa by gavage for 15 days. Group II was further divided into subgroup IIa and subgroup IIb. Subgroup IIa included seven mature 12-month-old adult rats weighing 600-650 g that received plain water by gavage for 15 days. Subgroup IIb included seven mature adult rats that received 2 ml/kg body weight of 1% petroleum ether extract of N. sativa by gavage for 15 days. Thymi from different subgroups were processed for histological, immunohistochemical, and morphometric studies. In subgroup Ib, the thymus of N. sativa-treated rats revealed a significant increase in the number of CD3-positive cells in the cortex. Some CD3-positive cells were seen in the medulla. In subgroup IIa, signs of thymic involution in the form of expansion of perivascular spaces containing adipocytes and stromal cells with a significant decrease in the number of CD3-positive cells were noticed. In addition, CI cells non reticular thymulin secreting cells along the capillaries were detected. In N. sativa-treated adult rats [subgroup IIb], restoration of the normal stroma and parenchyma occurred. Moreover, a significant increase in the number of CD3-positive cells in the cortex and medulla with an increase in the secretory activity of reticuloepithelial cells was noticed. Oral administration of the petroleum ether extract of N. sativa for 15 days to young and mature adult rats results in enhanced proliferation of thymocytes and increased activity of reticuloepithelial cells