**3. Conclusions**

Several new roles have been discovered and added to the complex knowledge about T and B cells. These include different functions of Tregs, the role of γδ T cells in gingival homeostasis, the role of SOFAT in osteoclastogenesis, and the possible pathogenic role of MAIT cells. Also, the importance of B cells activating RANKL-mediated bone resorption adds to this complex scenario. During periodontal inflammation, the activation of distinct T and B-cell subtypes, as well as their cytokine production, are crucial in defining whether the inflammatory lesion will stabilise as chronic gingivitis or progress to tissue-destructive periodontitis.

**Funding:** This research received no external funding. **Conflicts of Interest:** The authors declare no conflict of interest.
