**5. Conclusions**

Our findings suggest that aerobic exercise-induced changes in the distribution of specific naïve and memory B and T cell subsets, as well as in the proportions of activated T and regulatory T subsets, may indicate a retuned immune regulation and a presumably enhanced responsiveness of the immune system. On the other hand, as a low-impact workout, Pilates may influence the proportions of regulative T cells only. Nevertheless, based on the significant effects on immune regulation, Pilates exercise may also be beneficial in maintaining appropriate adaptive immune functions. However, taking into consideration that numerous complex factors, such as hormonal status, environmental factors, etc., may affect the immune system and might influence the effects of exercise, we have to mention the lack of non-exercise control group as one of the limitations of the study. Although our results showed significant changes in B and T cell subpopulations even with a relative small sample size, more controlled investigations are needed for the deeper understanding of exercise-induced changes in the distribution of naïve and memory lymphocytes, as well as in the regulatory functions that may have an important role in preventing infections and optimizing vaccination.

**Author Contributions:** Conceptualization, L.B. (László Balogh) and G.P.; methodology, K.S., I.J. and L.B. (Lilla Barna); software, K.S.; investigation, K.S., J.M.P. and M.M.; resources, G.P. and L.B. (László Balogh); data curation, K.S. and M.M.; writing—original draft preparation, K.S. and G.P.; writing—review and editing, L.B. (László Balogh), P.S., T.T. and Z.C.; visualization, K.S. and Á.G.; supervision, G.P. and L.B. (László Balogh); funding acquisition, G.P., L.B. (László Balogh) and Z.C. All authors have read and agreed to the published version of the manuscript.

**Funding:** The research was supported by the TKP2021-EGA-20 project, which was implemented with the support provided from the National Research, Development and Innovation Fund of Hungary, financed under the TKP2021-EGA funding scheme. The work of GP was supported by the János Bolyai Research Scholarship of the Hungarian Academy of Sciences and the ÚNKP-20-5 New National Excellence Program of the Ministry for Innovation and Technology.

**Institutional Review Board Statement:** The study was conducted according to the guidelines of the Declaration of Helsinki and approved by the Ethics Committee of the University of Debrecen (protocol number: 4839-2017, date of approval: 26 June 2017) and the Policy Administration Services of Public Health of the Government Office (registration number: 25040-4/2017/EÜIG, date of approval: 4 September 2017).

**Informed Consent Statement:** Informed written consent was obtained from all subjects enrolled in the investigation.

**Data Availability Statement:** The data presented in this study are available in the article's Figures and Tables.

**Acknowledgments:** The authors would like to thank all volunteers who participated in the study.

**Conflicts of Interest:** The authors declare that there is no conflict of interest regarding the publication of this paper.
