Semaphorin 4A Stabilizes Human Regulatory T Cell Phenotype via Plexin B1

Abstract

We previously reported that neuroimmune semaphorin (Sema) 4A regulates the severity of experimental allergic asthma and increases regulatory T (Treg) cell numbers in vivo; however, the mechanisms of Sema4A action remain unknown. It was also reported that Sema4A controls murine Treg cell function and survival acting through neuropilin 1 (NRP-1) receptor. To clarify Sema4A action on human T cells, we employed T cell lines (HuT78 and HuT102), human PBMCs, and CD4 + T cells in phenotypic and functional assays. We found that HuT78 demonstrated a T effector-like phenotype (CD4 + CD25 low Foxp3 2), whereas HuT102 expressed a Treg-like phenotype (CD4 + CD25 hi Foxp3 +). Neither cell line expressed NRP-1. HuT102 cells expressed Sema4A counter receptor Plexin B1, whereas HuT78 cells were Sema4A +. All human peripheral blood CD4 + T cells, including Treg cells, expressed PlexinB1 and lacked both NRP-1 and-2. However, NRP-1 and Sema4A were detected on CD3 negative CD4 intermediate human monocytes. Culture of HuT cells with soluble Sema4A led to an upregulation of CD25 and Foxp3 markers on HuT102 cells. Addition of Sema4A increased the relative numbers of CD4 + CD25 + Foxp3 + cells in PBMCs and CD4 + T cells, which were NRP-1 negative but PlexinB1 + , suggesting the role of this receptor in Treg cell stability. The inclusion of anti-PlexinB1 blocking Ab in cultures before recombinant Sema4A addition significantly decreased Treg cell numbers as compared with cultures with recombinant Sema4A alone. Sema4A was as effective as TGF-b in inducible Treg cell induction from CD4 + CD25 depleted cells but did not enhance Treg cell suppressive activity in vitro. These results suggest strategies for the development of new Sema4A-based therapeutic measures to combat allergic inflammatory diseases. ImmunoHorizons, 2019, 3: 71-87.

Identifying Function Determining Residues in Neuroimmune Semaphorin 4A

“…As expected, WT Sema4A displayed a highly specific effect on Treg cells, as it increased the relative number of CD4+Foxp3+ cells among PBMCs from 3.96 ± 0.46% in cultures with medium only to 6.18 ± 0.58% in cultures with 100 ng of WT Sema4A (Figure 8A,C). At the same time, the M198A Sema4A mutant demonstrated a more modest effect on the relative number of Tregs to 6.07 ± 0.61% of The mutant proteins were tested for their stimulatory effect on Treg cells in PBMC cultures, as described previously [17]. As expected, WT Sema4A displayed a highly specific effect on Treg cells, as it increased the relative number of CD4+Foxp3+ cells among PBMCs from 3.96 ± 0.46% in cultures with medium only to 6.18 ± 0.58% in cultures with 100 ng of WT Sema4A (Figure 8A,C).…”

Perspectives and potential approaches for targeting neuropilin 1 in SARS-CoV-2 infection

“…Mouse NRP1 is a critical receptor for Sema4A acting on Treg cells to regulate their stability and function (Delgoffe et al 2013 ). In humans, Plexin B1 plays this Sema4A-dependent potentiating function for Treg cells which lack NRP1 expression (Chapoval et al 2019 ). NRP1 is also expressed on CD4 low PBMC-derived human monocytes (Chapoval et al 2019 ).…”

“…In humans, Plexin B1 plays this Sema4A-dependent potentiating function for Treg cells which lack NRP1 expression (Chapoval et al 2019 ). NRP1 is also expressed on CD4 low PBMC-derived human monocytes (Chapoval et al 2019 ). Therefore, these monocytes might potentially get infected with SARS-CoV-2 virus although the ACE-2 expression on these cells has not been assessed.…”

Semaphorin4A-Plexin D1 Axis Induces Th2 and Th17 While Represses Th1 Skewing in an Autocrine Manner

“…Sema4A is mainly produced by dendritic cells, monocytes and macrophages [ 11 ], although it can be also expressed by activated CD4 + T cells and germinal center B cells [ 12 , 13 , 14 ]. Sema4A binds to different receptors expressed on CD4 + T cells, such as PlexinB1, PlexinB2, PlexinD1, Neuropilin-1 (NRP-1), Immunoglobulin-like transcript 4 (ILT)4 and Tim-2, although the last has been reported in mice and has no human orthologous [ 12 , 13 , 14 , 15 , 16 , 17 , 18 ]. Several studies have shown that Sema4A expression is elevated in diseases in which Th cells play an essential role, including asthma, RA, MS and SSc [ 11 , 12 , 13 , 19 ].…”