Immune Checkpoint Expression Patterns on T Cell Subsets in Light-Chain Amyloidosis: VISTA, PD-1, and Tigit As Potential Therapeutic Targets

Abstract

Background: Systemic immunoglobulin light chain amyloidosis (AL amyloidosis) is a rare plasma cell dyscrasia with a poor prognosis. T-cell exhaustion can lead to impaired T cell-mediated antitumor immunity, but there is limited information available regarding the T-cell immunodeficiency status in AL amyloidosis. This study aims to investigate the T-cell immune checkpoint expression patterns in AL amyloidosis and its relationship with clinicobiological characteristics.

Methods: Using multi-color fluorescent flow cytometry, we examined the expression levels of V-domain immunoglobulin suppressor of T cell activation (VISTA), programmed death 1 (PD-1), T cell immunoglobulin and mucin-domain-containing-3 (Tim-3), T cell immunoreceptor with Ig and ITIM domains (TIGIT) on CD3+, CD4+, CD8+ T-cell, and regulatory T cell (Treg) in peripheral blood (PB) and bone marrow (BM) from 19 patients with newly diagnosed AL amyloidosis. We used 36 PB and BM samples from patients with newly diagnosed multiple myeloma (MM) and 19 PB and 10 BM samples from healthy individuals (HIs) as controls.

Results: Our results showed that PB from patients with AL amyloidosis had significantly higher percentages of VISTA+ and PD-1+ subsets within CD3+, CD4+, CD8+ T cells and Tregs when compared to HIs. No statistical differences for frequency of VISTA+, PD-1+, Tim-3+ and TIGIT+ T-cell in BM were observed between the two groups. The percentages of double-positive VISTA+ PD-1+, VISTA+ Tim-3+, VISTA+ TIGIT+, PD-1+ Tim-3+ and PD-1+ TIGIT+ T cells in PB from the patients with AL amyloidosis were also considerably higher than those in the HIs. Moreover, we discovered that the patients with renal involvement had greater percentages of PD-1+ or TIGIT+ subsets within CD3+, CD4+ T cells and Tregs than the individuals without renal involvement. Additionally, PD-1+CD3+%, PD-1+CD4+%, and PD-1+Treg% were found to be positively correlated with 24-hour proteinuria levels. Furthermore, we observed that the AL amyloidosis patients had significantly higher counts of PD-1+ Treg in PB than the MM patients, while the MM patients had significantly higher counts of TIGIT+ subsets within CD3+, CD4+ and CD8+ T cells than the AL amyloidosis patients.

Conclusions: Our findings suggest that there are elevated proportions of VISTA+ and PD-1+ T cells in PB of AL amyloidosis patients, which are indicators of an immunosuppressive milieu. The rise in PD-1+ or TIGIT+ T cells was associated with renal damage. Notably, MM and AL amyloidosis have very distinct immunosuppressive patterns based on immune checkpoint alteration. Overall, VISTA, PD-1, and TIGIT may be considered as potential targets for reversing T cell exhaustion and enhancing T cell activity in AL amyloidosis.