Abstract
Dendritic cells (DCs) are innate immune cells which engulf, process and present antigens to the naïve T-lymphocyte cells. However, little is known about the effect of melatonin on the DCs. The present study aimed to investigate the morphology and distribution of the DCs by transmission electron microscopy and Immunohistochemistry after melatonin administration. A total of 8 out of 15 adult ram was randomly selected to receive the melatonin implant and the remaining 7 animals received melatonin free implants. DCs showed positive immunoreactivity for CD117, S-100 protein and CD34. There is an obvious increase in the number of the positive immunoreactive cells to CD3, estrogen receptor alpha and progesterone in the treated groups. The expression of CD56 and MHCII in the DCs was abundant in the treated groups. The ultrastructure study revealed that melatonin exerts a stimulatory effect on the DCs which was associated with increment in the secretory activity of DCs. The secretory activity demarcated by an obvious increase in the number of mitochondria, cisternae of rER and a well-developed Golgi apparatus. The endosomal- lysosomal system was more developed in the treated groups. A rod-shaped Birbeck granule was demonstrated in the cytoplasm of the melatonin treated group. DCs were observed in a close contact to telocytes, T-Lymphocytes, nerve fibers and blood vessels. Taken together, melatonin administration elicits a stimulatory action on the DCs and macrophages through increasing the size, the number and the endosomal compartments which may correlate to increased immunity.
Highlights
Dendritic cells (DCs) are innate immune cells which engulf, process and present antigens to the naïve T-lymphocyte cells
In the paraffin sections stained with H&E of the control groups, the dendritic cells were demonstrated residing among the glandular epithelium lining the seminal vesicle
The movable DCs were larger in size and more abundant in the melatonin treated groups when compared to the control (Fig. 3D,E and Table 2)
Summary
Dendritic cells (DCs) are innate immune cells which engulf, process and present antigens to the naïve T-lymphocyte cells. There is an obvious increase in the number of the positive immunoreactive cells to CD3, estrogen receptor alpha and progesterone in the treated groups. Melatonin (5-methoxyN-acetyltryptamine) regulates the circadian rhythm and the seasonal changes via its nocturnal synthesis by the pineal gland. It is involved in many pathways including antiaging, antioxidant, free radical scavenger, anticarcinogenic and immunomodulatory e ffects[27,28,29]. In our previous study we investigated a significant increase in the number of dendritic cells and its phagocytic vesicles in the adrenal gland of melatonin treated groups of Soay r am[33]. The exogenous melatonin treatment during the non-breeding season increases the testosterone level in the blood plasma[35,36], the sperm quality, the testicular parameters, the spermatogenesis and fertility of rams during the long day’s p eriods[37,38]
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