Bone marrow CD3+ CD56+ regulatory T lymphocytes (TR3 -56 cells) are inversely associated with activation and expansion of bone marrow cytotoxic T cells in IPSS-R very-low/low risk MDS patients

Abstract

Background: Emergence of dysplastic haematopoietic precursor/s, cytopenia and variable leukaemia risk characterise myelodysplastic syndromes (MDS). Impaired immune-regulation, preferentially affecting cytotoxic T cells (CTL), has been largely observed in MDS. Recently, we described the T_R3-56 T cell subset, characterised by the co-expression of CD3 and CD56, as a novel immune-regulatory population, able to modulate cytotoxic functions. Here, we address the involvement of T_R3-56 cells in MDS pathogenesis/progression.

Objectives: To analyse the relationship between T_R3-56 and CTL activation/expansion in bone marrow (BM) of very-low/low-risk MDS subjects.

Methods: Peripheral blood and BM specimens, obtained at disease onset in a cohort of 58 subjects, were analysed by immune-fluorescence and flow cytometry, to preserve the complexity of the biological sample.

Results: We observed that a trend-increase of BM T_R3-56 in high/very-high MDS stage, as compared with very-low/low group, associates with a decreased activation of BM resident CTL; significant correlation of T_R3-56 with BM blasts has been also revealed. In addition, in very-low/low-risk subjects the T_R3-56 amount in BM inversely correlates with the presence of activated BM CTL showing a skewed Vβ T-cell repertoire.

Conclusions: These data add T_R3-56 to the immune-regulatory network involved in MDS pathogenesis/progression. Better knowledge of the immune-mediated processes associated with the disease might improve MDS clinical management.

Keywords: T lymphocytes regulatory; bone marrow; cytotoxic T-lymphocytes; myelodysplastic syndrome.

FIGURE 1

BM T_R3−56 lymphocyte percentage positively correlates with BM blast number and seems to be inversely associated with BM CD54 expression on BM CTL in MDS subjects. (A) White, grey and black columns indicate BM percentage of T_R3−56 cell subset in very‐low/low risk (N 46), intermediate risk (N 5) and high/very‐high risk (N 7) MDS patients, respectively. (B) White, grey and black columns indicate CD54 expression on BM CTL in very‐low/low risk (N 46), intermediate risk (N 5) and high/very‐high risk (N 7) MDS patients, respectively. As shown, an increasing trend of BM T_R3−56 percentage accompanied by a decreasing trend for CD54 expression on CTL is observed from very‐low/low risk to high/very‐high risk group. (C) Spearman's evaluation of correlation between BM T_R3−56 cell subset percentage and BM blast in MDS subjects. As shown, a significant (p < .005) positive correlation (r = .433) has been revealed

FIGURE 2

T_R3−56 lymphocyte percentage in BM of very‐low/low risk MDS patients inversely correlates with CD54 expression on BM CTL. Left part of the figure shows very‐low/low risk MDS patients grouping according to CD54 expression on BM CTL, as previously described. (A–D) Analysis of BM versus blood CD3⁺CD8⁺ and T_R3−56 in the very‐low/low risk MDS patients, grouped according to their CD54 expression on BM CTL. White and grey columns indicate BM and PB percentage, respectively. (A and B) Analysis of BM versus blood CTL distribution in the subjects categorised according their CD54 expression on BM CTL; (C and D) analysis of BM versus blood T_R3‐56 distribution in the subjects categorised according their CD54 expression on BM CTL. As shown, significant BM recruitment of CTL (p < .0001) and T_R3−56 (p < .05) lymphocytes has been observed only in the subjects with lower CD54 expression on BM CTL

FIGURE 3

Spearman's correlation analysis of BM T_R3−56 lymphocytes, BM CTL percentage and activation in very‐low/low risk MDS patients categorised according to the presence of a preferential BM T cell skewed Vβ repertoire. (A) Spearman correlation analysis of CD54 expression on BM CTL versus BM T_R3−56 percentage in MDS subjects with ≥2 CTL Vβ skewed clones in BM; significant negative correlation (Spearman r = −.723; p < .05) is shown. (B) Spearman correlation analysis of BM T_R3−56 RI (ratio between the percentage of T_R3‐56 lymphocytes in BM vs. their percentage in PB) versus BM CTL percentage in MDS subjects with ≥2 CTL Vβ skewed clones in BM; significant negative correlation (Spearman r = −.948; p < .0001) is revealed. (C) Spearman correlation analysis of BM T_R3−56 vs BM T_R3‐56 percentage in MDS subjects with <2 CTL Vβ skewed clones in BM; significant positive correlation (Spearman r = .701; p < .05) is observed. (D) Spearman correlation analysis of BM CTL RI versus BM CTL percentage in MDS subjects with ≥2 CD4⁺ Vβ skewed clones in BM; significant positive correlation (Spearman r = .903; p < .005) is shown