In practical terms, our immune system is nothing more than the body's defense against infectious organisms and other invading agents, and it is activated in situations where our metabolism detects that foreign invading substances, scientifically called antigens, have entered the body.
Specifically from the biological point of view, antigens are external substances that have the potential to trigger the formation of antibodies, an action that activates an immune response in our metabolism.
Now, regarding the topic outlined in the title of this publication related to whether mushrooms exhibit antioxidant capacity capable of activating our immune system, it is to communicate that according to multiple studies of anticancer character it is inferred that mushrooms possess antioxidant capacity that helps slow the growth of cancer cells.
Fig. 2 Mushrooms exhibit antioxidant capacity capable of activating our immune system. Image of public domain, Author: Myriams-Jarmoluk, 2014
It is known that mushrooms exhibit various nutritional and medicinal properties, therefore, attributing that mushrooms can slow the progression of cancer is not something that causes surprise, since in nature are hidden the keys and answers to the many conditions that afflict the health of us humans.
Fig. 3 Fungi may slow cancer progression. Image of public domain, Author: Myriams- Maleni_ferrari, 2017
From the metabolic point of view, mushrooms contain polysaccharides, proteins, tocopherols, glycosides, folic acid, enzymes, alkaloids, flavonoids, carotenoids, sterols (precursors of positive hormones) and an inexhaustible antioxidant and anticancer capacity in gastric, breast and lung pathologies, an element that gives positive signals to the pharmaceutical sector in the search for the design of new mushroom-based anticancer drugs.
BIBLIOGRAPHICAL REFERENCES CONSULTED:
 Ayeka P Potential of Mushroom Compounds as Immunomodulators in Cancer Immunotherapy: A Review. Evidence-based Complementary and Alternative Medicine. 2018; 1: 1 - 9. Article: Online access
 Blagodatski A Medicinal mushrooms as an attractive new source of natural compounds for future cancer therapy. Article: Online access