A conserved human CD4+ T cell subset recognizing the mycobacterial adjuvant trehalose monomycolate
Yuki Sakai, … , Go Hirai, Sho Yamasaki
Yuki Sakai, … , Go Hirai, Sho Yamasaki
Published December 24, 2024
Citation Information: J Clin Invest. 2025;135(6):e185443. https://doi.org/10.1172/JCI185443.
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Research Article Immunology Infectious disease

A conserved human CD4+ T cell subset recognizing the mycobacterial adjuvant trehalose monomycolate

Abstract

Mycobacterium tuberculosis causes human tuberculosis (TB). As mycobacteria are protected by a thick lipid cell wall, humans have developed immune responses against diverse mycobacterial lipids. Most of these immunostimulatory lipids are known as adjuvants acting through innate immune receptors, such as C-type lectin receptors. Although a few mycobacterial lipid antigens activate unconventional T cells, the antigenicity of most adjuvantic lipids is unknown. Here, we identified that trehalose monomycolate (TMM), an abundant mycobacterial adjuvant, activated human T cells bearing a unique αβ T cell receptor (αβTCR). This recognition was restricted by CD1b, a monomorphic antigen-presenting molecule conserved in primates but not mice. Single-cell TCR-RNA-Seq using newly established CD1b-TMM tetramers revealed that TMM-specific T cells were present as CD4+ effector memory T cells in the periphery of uninfected donors but expressed IFN-γ, TNF, and anti-mycobacterial effectors upon TMM stimulation. TMM-specific T cells were detected in cord blood and PBMCs of donors without bacillus Calmette-Guérin vaccination but were expanded in patients with active TB. A cryo-electron microscopy study of CD1b-TMM-TCR complexes revealed unique antigen recognition by conserved features of TCRs, positively charged CDR3α, and long CDR3β regions. These results indicate that humans have a commonly shared and preformed CD4+ T cell subset recognizing a typical mycobacterial adjuvant as an antigen. Furthermore, the dual role of TMM justifies reconsideration of the mechanism of action of adjuvants.

Authors

Yuki Sakai, Minori Asa, Mika Hirose, Wakana Kusuhara, Nagatoshi Fujiwara, Hiroto Tamashima, Takahiro Ikazaki, Shiori Oka, Kota Kuraba, Kentaro Tanaka, Takashi Yoshiyama, Masamichi Nagae, Yoshihiko Hoshino, Daisuke Motooka, Ildiko Van Rhijn, Xiuyuan Lu, Eri Ishikawa, D. Branch Moody, Takayuki Kato, Shinsuke Inuki, Go Hirai, Sho Yamasaki

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Figure 7

TMM-specific T cells with similar characteristics are shared among individuals.

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TMM-specific T cells with similar characteristics are shared among indiv...
(A and B) Frequent TMM-specific clonotypes identified by TMM-CD1b-tetramer sorting and scTCR-RNA-Seq are overlaid (A) on a UMAP plot of all TMM-tetramer–sorted T cells and unsorted CD3+ T cells from 13 healthy donors (B). Three clones were detected from different individual donors; 2 clones (clones 17 and 439) were from another donor. CD4+ Tem, CD4+ effector memory T cells; CD4 Tcm, CD4+ central memory T cells. Naive T cells were rare within TMM-tetramer+ cells and were not clustered on the UMAP. (C) TCR usages, CDR3 sequences, and length of the CDR3β region of the clonotypes detected in A. (D) Each clonotype was reconstituted into reporter cells and analyzed for TMM, TDM, and GMM reactivity using CD1b-DC2.4 as APCs. Data are shown as the mean ± SD of triplicate assays, and representative results from 2 independent experiments are shown. Reporter cells were stained with PE-conjugated endo-CD1b (Cont.) or TMM-CD1b (TMM) tetramers and anti-CD3 antibodies. Y-50 TCR is shown as a control. (E and F) Frequency of TCRVβ usage (D) and length of the CDR3β region (E) of unsorted or the top 27 TMM-CD1b tetramer+ T cell clonotypes. (G) PBMCs from Japanese donors (uninfected donors, n = 7; patients with TB, n = 13) or PBMCs (n = 10) and cord blood cells (n = 10) from uninfected US donors were stained with PE-conjugated TMM-loaded CD1b tetramer, APC-conjugated CD1b-endo tetramer and anti-CD3 antibody. The percentages of TMM-CD1b tetramer+ and endo-CD1b tetramer– populations in CD3+ T cells are shown (TMM-CD1b-tet+). Medians are indicated with horizontal bars. *P < 0.05, by unpaired, 2-tailed Welch’s t test.