Editorial: The relationships between physical activity, exercise, and sport on the immune system

During their lifetime, human beings are exposed to different microorganisms (i.e., virous, bacteria, fungi, and germs), parasites, and cancerous cells. This exposure endows the immunological system with the ability to differentiate what may be accepted or rejected by the human body, which in turn is controlled byantigens and antibodies. Antigens are any substance that the human immune system may recognize to stimulate an immunological response while antibodies are B-cell proteins responsible for identifying and marking the invader agent (i.e., antigen) to be neutralized or eliminated by the immune system. Exposure to different pathogenic agents may have two different outcomes: the exposure may result in improving the immunological resistance, or the exposure may increase the inflammatory response.This research was founded by the Higher Institute of Educational Sciences of the Douro and by national funds (FCT—Portuguese Foundation for Science and Technology) under the project UIBD/DTP/04045/2020.