The initial formation of Aire+ mTECs depended on RANK signals, whereas the continued mTEC development to the involucrin+ stage was mapped to the activation of lymphotoxin β receptor (LTβR) signals provided by mature thymocytes [25]. Lkhagvasuren et al. reported that CCL21-expressing mTECs contained a cell population distinct from Aire-expressing mTECs and that the accumulation of this CCL21+ Aire– mTEC subpopulation occurred late during postnatal ontogeny [26]. It was also noted that the postnatal accumulation LDK378 chemical structure of CCL21+ Aire– mTECs was regulated by LTβR signals [26], of which the ligand lymphotoxin was provided

by positively selected thymocytes [25]. The temporally regulated heterogeneity of mTECs may be linked with the developmental switch of hematopoietic cells (e.g. mature thymocytes or lymphoid tissue inducer cells) that provide different cytokine ligands [8, 27]. Further studies will help us understand the FK506 cellular and molecular mechanisms for the development of the heterogeneous mTEC subpopulations. The results presented by Ribeiro et al. [18] have sparked many interesting questions. Regarding CCRL1 expression in mTEC progenitors, the molecular mechanisms underlying the induction of many cTEC-associated molecules in mTEC progenitors and the termination of their expression

in mTEC progenies remain unsolved. Regarding the complexity in mTECs, how CCRL1-EGFPlow mTECs are related to previously described mTEC subpopulations and what functions CCRL1-EGFPlow mTECs play in the thymus by the low expression of CCRL1 are left unanswered. It should also be noted that whether the new CCRL1-EGFPlow “mTECs” are indeed localized in the thymic medulla is still an open question. This study was supported by Grants-in-Aid for Scientific Research from MEXT and JSPS (23249025, 24111004, and 25860361). The authors declare no conflict of interest. “
“Previous studies

from our laboratory demonstrated that treatment in vitro with recombinant guinea pig tumour necrosis factor TNF (rgpTNF)-α-enhanced to T cell and macrophage functions. Similarly, injection of Mycobacterium tuberculosis-infected guinea pigs with anti-TNF-α altered splenic granuloma organization and caused inflammatory changes and reduced the cell-associated mycobacteria in the tuberculous pluritis model. In this study, rgpTNF-α was injected into bacille Calmette–Guérin (BCG)-vaccinated guinea pigs to modulate immune functions in vivo. Guinea pigs were vaccinated intradermally with BCG, 2 × 103 colony-forming units (CFU) and injected intraperitoneally with either rgpTNF-α (25 µg/animal) or 1% bovine serum albumin (BSA) for a total of 12 injections given every other day. Treatment with rgpTNF-α significantly enhanced the skin test response to purified protein derivative (PPD), reduced the number of CFUs and increased the PPD-induced proliferation in the lymph nodes at 6 weeks after vaccination.