A number of lines of research suggest that forms of calorie restriction and fasting can improve the function of the immune system. It is also noted that fasting can reduce the number of immune cells found in the circulation. The complement system is a part of the innate immune system, reacting to invading pathogens in order to rouse immune cells to action. Red blood cells play a part in the complement system, and researchers here show that fasting can improve the immune response despite a lower number of circulating white blood cells by improving the ability of red blood cells to trigger a response.
Fasting is known to influence the immune functions of leukocytes primarily by regulating their mobilization and redistribution between the bone marrow and the peripheral tissues or circulation, in particular via relocalization of leukocytes back in the bone marrow. However, how the immune system responds to the increased risk of invasion by infectious pathogens with fewer leukocytes in the peripheral blood during fasting intervention remains an open question.
We used proteomic, biochemical and flow cytometric tools to evaluate the impact of short-term intensive fasting (STIF), known as beego, on red blood cells by profiling the cells from the STIF subjects before and after 6 days of fasting and 6 days of gradual refeeding. We found that STIF, by triggering the activation of the complement system via the complement receptor on the membrane of red blood cells, boosts fairly sustainable function of red blood cells in immune responses in close relation to various pathogens, including viruses, bacteria, and parasites, particularly with the pronounced capacity to defend against SARS-CoV-2, without compromising their oxygen delivery capacity and viability.