Physical activity and exercise are especially important in maintaining health and reducing risk of many diseases. Exercise leads to a pronounced immunomodulation by affecting the elements of innate immune system, as well as the ratio and functions of neutrophils, macrophages, natural killer cells, which are involved in the development, maintenance and elimination of inflammation. In the adaptive immune system, Th1 / Th2 balance shift toward Th2, and high-intensity training causes an increase in the proportion of regulatory T cells, as opposed to the effect of non-strenuous exercise on the Treg cell ratio. In response to exercise, there is a lack of data on B cells, but some studies have reported a decrease in immunoglobulin secretion. In our own research we observed changes in naive and memory B cell ratios. Upon exercise, IL-6, as proinflammatory cytokine, promotes T cell proliferation, activation, and differentiation of B cells into antibody-producing plasma cells. Hormonal factors play an important role in the background of immunological changes. Exercise stimulates the secretion of both adrenaline and noradrenalin, and their concentration in the blood is directly proportional to the duration of exercise. Endurance exercise is associated with increased cortisol levels, while low intensity exercise does not significantly affect cortisol levels. Exercise and physical stress can increase the concentration of endorphins by 3 to 10 times; β-endorphin inhibits T and B cell activity, thus reduces antibody production. Testosterone causes a reduction in antibodies to IL-4, IL-5, IFN-γ, Ig-M and Ig-G. Based on the above, mild to moderate physical activity contributes to the enhancement of immune reactivity and the immune response. On the other hand, strenuous exercise with increased intensity leads to a deterioration of immune function and impaired immunological defense.