how does it affect immune system?
An antiinflammatory effect seems to be the most relevant.
Immune system
While it is known that melatonin interacts with the immune system, the details of those interactions are unclear. An antiinflammatory effect seems to be the most relevant. 
the primary high energy molecule in human metabolism is Adenosine triphosphate (ATP) what is catabolism? It is the set of metabolic processes that breaks down large molecules. which hormones are related to it? Cortisol, glucagon, adrenaline, cytokines, orexin and melatonin. what is the emotional response due to the third one? Fear. how does the first hormone related to metabolism of glucose? Cortisol stimulates the synthesis of 'new' glucose from non-carbohydrate sources; this is known as gluconeogenesis.. is process resisted by insulin? Yes. when was this substance which resists the process discovered? 1921. can it be extracted? Yes. from where? Pancreas. can we find in plants the last hormone in the list of hormones mentioned above? Yes. is it responsible for any memory related disease? No.
An antiinflammatory effect seems to be the most relevant. While it is known that melatonin interacts with the immune system, the details of those interactions are unclear. An antiinflammatory effect seems to be the most relevant. It has an anti-inflammatory effect.
Melatonin Melatonin Melatonin
Immune system Immune system Immune system
. An antiinflammatory effect seems to be the most relevant.  While it is known that melatonin interacts with the immune system, the details of those interactions are unclear. An antiinflammatory effect seems to be the most relevant.  An antiinflammatory effect seems to be the most relevant. 
wiki:19892677
Melatonin [SEP] Immune system
While it is known that melatonin interacts with the immune system, the details of those interactions are unclear. An antiinflammatory effect seems to be the most relevant. There have been few trials designed to judge the effectiveness of melatonin in disease treatment. Most existing data are based on small, incomplete trials. Any positive immunological effect is thought to be the result of melatonin acting on high-affinity receptors (MT1 and MT2) expressed in immunocompetent cells. In preclinical studies, melatonin may enhance cytokine production, and by doing this, counteract acquired immunodeficiences. Some studies also suggest that melatonin might be useful fighting infectious disease including viral, such as HIV, and bacterial infections, and potentially in the treatment of cancer.