Towards Clinically Relevant Immune Biomarkers in Myeloproliferative Neoplasms: Methodological Considerations for Future Studies

We read with great interest the rigorous clinical study by Liang et al., which employed flow cytometry to correlate monocyte markers (such as CD16, CD11b, and CD64) with clinical parameters [1]. This research provides valuable insights into the immune microenvironment of myeloproliferative neoplasms (MPNs) and suggests potential prognostic markers—an important direction for clinical translation. While we commend these contributions, we wish to raise several points that could further strengthen the interpretation and generalizability of the findings. First, the geographic and sample representativeness should be considered. All samples were obtained from two hospitals in Shanxi Province, which may limit the geographical diversity of the cohort. Given China's substantial regional variations in genetic background, environmental exposures, and lifestyle, the findings might not be fully representative of the broader Chinese MPNs population [2]. Moreover, although the sample size is reasonable for a single-center study, it may still be inadequate to capture the full clinical and molecular heterogeneity of MPNs—especially in rare subtypes such as pre-fibrotic primary myelofibrosis (Pre-PMF). This limitation could affect the robustness of subgroup analyses and correlation findings. Future multi-center collaborations with larger sample sizes would help improve the generalizability of the results [3]. Incorporating genetic, transcriptomic, and environmental variables could also enhance the characterization of the immune microenvironment and its clinical implications in Chinese MPNs patients. Second, the lack of longitudinal follow-up limits the validation of the prognostic relevance of the identified markers. The study reports several correlations—for instance, between bone marrow monocyte proportion and fibrosis grade, and between CD15+ monocytes and International Prognostic Scoring System (IPSS) scores. However, without long-term follow-up, it remains unclear whether these immunophenotypic features can predict clinically relevant endpoints such as progression from Pre-PMF to overtly fibrotic PMF (Overt-PMF), thrombotic events, or leukemic transformation [4]. Prospective longitudinal data would greatly strengthen the clinical applicability of these markers, as demonstrated in previous MPNs prognostic studies [5, 6]. We propose that such future longitudinal studies would be ideally positioned to address this gap by incorporating a validated and expanded flow cytometry panel. Building on established immunophenotypic profiles [7, 8], such a panel should encompass markers for core monocyte subsets (e.g., CD14, CD16) and activation states (e.g., HLA-DR, CD64, CD11b). This approach would not only clarify the temporal relationship between immunophenotype and outcomes like fibrotic progression but also enable a multivariate analysis to determine whether markers beyond CD15+ monocytes, such as CD11b + or CD64+ subsets, offer independent or synergistic prognostic value alongside scores like IPSS or DIPSS. Ultimately, this strategy could pave the way for a composite “monocyte-based risk score” for disease progression [9]. Finally, the potential influence of subclinical inflammation and comorbidities remains unaccounted for. While the authors attribute increased CD16 expression in MPNs monocytes to “disease-related inflammation,” their interpretation does not account for subclinical inflammation or comorbidities [10]. Elevated inflammatory markers (such as C-reactive protein (CRP) and IL-6) are frequent in MPNs and are known to upregulate CD16 on monocytes in non-malignant contexts [10, 11]. This omission introduces ambiguity into the interpretation of the results. For example, in polycythemia vera/essential thrombocythemia cases, the positive correlation between CD16+ monocytes and patient age may reflect age-related chronic inflammation rather than the direct effect of MPNs. Future studies should integrate the measurement of systemic inflammation (such as CRP and IL-6 levels) and detailed comorbidity data into the analysis to distinguish MPNs-specific effects from non-malignant influences on the immune phenotype of monocytes. In summary, Liang et al.'s study provides a valuable foundation for exploring monocyte biology in Chinese MPNs patients. Addressing the above points—either through additional analyses or expanded discussion—would further strengthen its contribution to MPNs research and clinical practice. We appreciate the authors' efforts to advance this field and look forward to their response. This work was supported by Linping District First People's Hospital. The authors declare no conflicts of interest. Data sharing is not applicable to this article as no datasets were generated or analyzed during the current study.