How follicular T-helper (Tfh) cells develop is incompletely understood. We find that, upon antigen exposure in vivo, both naïve and antigen-experienced T cells sequentially upregulate CXCR5 and Bcl6 within the first 24 h, relocate to the T-B border, and give rise to phenotypic Bcl6+CXCR5+ Tfh cells before the first cell division. CXCR5 upregulation is more dependent on ICOS costimulation than that of Bcl6, and early Bcl6 induction requires T-cell expression of CXCR5 and, presumably, relocation toward the follicle. This early and rapid upregulation of CXCR5 and Bcl6 depends on IL-6 produced by radiation-resistant cells. These results suggest that a Bcl6hiCXCR5hi phenotype does not automatically define a Tfh lineage but might reflect a state of antigen exposure and non-commitment to terminal effector fates and that niches in the T-B border and/or the follicle are important for optimal Bcl6 induction and maintenance.Electronic supplementary materialThe online version of this article (doi:10.1007/s13238-015-0210-0) contains supplementary material, which is available to authorized users.

Follicular T helper (T) cells orchestrate the germinal center (GC) response locally. T localization in GCs is controlled by chemo-guidance cues and antigen-specific adhesion. Here. we define an antigen-independent, contact-dependent, adhesive guidance system for T cells. Unusual for amoeboid cell migration, the system is composed of transmembrane plexin B2 (PlxnB2) molecule, which is highly expressed by GC B cells, and its transmembrane binding partner semaphorin 4C (Sema4C), which is upregulated on T cells. Sema4C on T cells serves as a receptor to sense the GC-presented PlxnB2 cue and biases T migration inwards at the GC edge to promote GC access. The absence of PlxnB2 from the GC or Sema4C from T cells causes T accumulation along the GC border, impairs T-B cell interactions in the GC, and is associated with defective plasma cell production and affinity maturation. Therefore, Sema4C and PlxnB2 regulate GC T recruitment and function and optimize antibody responses.

HMBOX1 is a new member of the homeobox family. Homeobox members have been reported to participate in embryonic development and systemic metabolism, but the function of HMBOX1 remains unclear, especially in the hematopoietic system. Here, we show that HMBOX1 is expressed at a high level in primary human NK cells but is expressed at much lower levels in NK cell lines. Overexpression of HMBOX1 significantly inhibited NK cell activities, including natural cytotoxicity against tumor cells, the level of CD107a (a marker protein for degranulation) and the production of cytolytic proteins (perforin and granzymes). More interestingly, HMBOX1 negatively regulated the expression of NKG2D and the activation of the NKG2D/DAP10 signaling pathway in NK cells. This effect was reversed by knocking down HMBOX1. Taken together, these findings demonstrate that HMBOX1 may act as a negative regulator of NK cell functions via suppressing the NKG2D/DAP10 signaling pathway.

The germinal center response requires cooperation between Ag-specific T and B lymphocytes, which takes the form of long-lasting cell–cell conjugation in vivo. Signaling lymphocytic activation molecule (SLAM)–associated protein (SAP) is required for stable cognate T–B cell conjugation, whereas SLAM family transmembrane (TM) receptor Ly108 may negatively regulate this process. We show that, other than phosphotyrosine-binding, SAP does not harbor motifs that recruit additional signaling intermediates to stabilize T–B adhesion. Ly108 dampens T cell adhesion to not only Ag-presenting B cells, but also dendritic cells by inhibiting CD3ζ phosphorylation through two levels of regulated Ly108–CD3ζ interactions. Constitutively associated with Src homology 2 domain–containing tyrosine phosphatase-1 even in SAP-competent cells, Ly108 is codistributed with the CD3 complex within a length scale of 100–200 nm on quiescent cells and can reduce CD3ζ phosphorylation in the absence of overt TCR stimulation or Ly108 ligation. When Ly108 is engaged in trans during cell–cell interactions, Ly108–CD3ζ interactions are promoted in a manner that uniquely depends on Ly108 TM domain, leading to more efficient CD3ζ dephosphorylation. Whereas replacement of the Ly108 TM domain still allows the constitutive, colocalization-dependent inhibition of CD3ζ phosphorylation, it abrogates the ligation-dependent Ly108–CD3ζ interactions and CD3ζ dephosphorylation, and it abolishes the suppression on Ag-triggered T–B adhesion. These results offer new insights into how SAP and Ly108 antagonistically modulate the strength of proximal TCR signaling and thereby control cognate T cell–APC interactions.

HMBOX1 was a novel transcription factor possibly involving in function of pancreas and cytotoxicity of NK cells. For function determination, recombinant human HMBOX1 protein was obtained and purified, and the monoclonal antibodies against HMBOX1 were prepared. The full-length cDNA fragment encoding HMBOX1 was amplified from NK-92 cells and inserted into prokaryotic expression vector pET22b. The pET22b-HMBOX1-6his vector was then transformed into E. coli Rosetta (DE3) and induced by 1 mM IPTG for 4 h at 37 o C. The fusion HMBOX1 protein was mainly expressed in inclusion bodies, which was purified and refolded using Ni 2+ -affinity chromatography. With the purified fusion HMBOX1 protein as antigen, monoclonal antibodies against HMBOX1 were generated, providing a potentially useful tool for further study in HMBOX1 functions. Using these anti-HMBOX1 mAbs, we identified that HMBOX1 is located in both cytoplasm and nucleus and could be detected in 10 human normal tissues, including cerebrum, pancreas, kidney and liver tissues. Moreover, the expression in hepatic carcinoma was significantly lower than that in adjacent tissues. Cellular & Molecular Immunology. 2009; 6(4):261-268.

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We have designed a series of dynamic mechanical analysis (DMA)-like device to directly measure the material properties of living human plantar soft tissue. Various mechanical tests of plantar soft tissue such as vertical, horizontal shear and torsion can be carried out on the newly invented instruments, and periodic strain-stress outputs are obtained to analyse the viscoelasticity of the tissue. Pioneering finite element analysis has been done by coupling the machine and human foot FE model from different simulation environments, and the simulation tests show good engineering verification of the device design, and consistent theoretical results of the material properties of plantar soft tissue as expected.

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