Background: In classical Hodgkin lymphoma (cHL) the malignant cells represent only a small fraction of the tumor mass. Yet, they orchestrate a lymphocyte-dominated tumor microenvironment (TME) that supports their survival and growth. The systemic effects of this local immunomodulation are not fully elucidated. In this study, we aimed at characterising circulating lymphocytes and plasma proteins in cHL patients in relation to clinical parameters and treatment effect.
Methods: Peripheral blood (PB) samples were obtained from 48 consecutive patients at diagnosis (baseline, BL) and at 2 time points after primary treatment, right at the end of treatment (EoT) and at follow-up 6 months after EoT (FU). Twenty-eight patients had limited-stage (I-IIA) and 20 had advanced-stage (IIB-IV) disease. All the patients in the FU analysis were in complete remission. Twenty healthy individuals were included as controls. Cells from PB and LN were freshly analysed by flow cytometry, and plasma proteins by proximity extension assay (PEA). Concentrations of CCL17/TARC in plasma were also measured by Enzyme-Linked ImmunoSorbent Assay.
Results: At BL, the numbers of B cells were lower in both limited- and advanced-stage cHL compared to controls, while T cells were normal. Advanced-stage patients had fewer NK cells with a functionally impaired phenotype. Compared to controls, cHL patients had higher frequencies of proliferating T cells as well as higher expression of programmed death (PD)-1 and cytotoxic T lymphocyte antigen (CTLA)-4 in circulating T cells, and lower naïve T-cell frequencies. The plasma concentration of CCL17/TARC was elevated in both limited- and advanced-stage cHL compared to controls. The frequencies of T and B cells positively correlated between the PB and LN compartments. Distinct immune cellular and plasma protein biomarker profiles were observed in patients with a high tumor burden (i.e. bulky tumor and/or >2 nodal sites involved and/or stage IV) and those with high inflammation (i.e. ESR ≥50). T-cell exhaustion and NK-cell depletion were reversed by standard first-line treatment and CCL17/TARC concentrations also dropped back to control levels. Patients who received radiotherapy involving the mediastinum had low T-cell counts for a prolonged period.
Conclusion: The immunomodulation of lymphocytes in the TME of cHL might affect immune biomarkers in the PB. Most immunological changes are reverted after successful standard primary treatment.