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Infection remains a leading cause of morbidity in multiple myeloma. Preventing infections is paramount and immune profiling could reflect the cumulative effect of host, tumor and treatment-related immunosuppression. However, current understanding of immune dysfunction and its association with infection is limited. To address this gap in knowledge and identify immune biomarkers of increased infection risk, we performed immune profiling using next-generation flow cytometry in bone marrow and peripheral blood samples from 1,786 patients at various disease stages and treatment scenarios. Patients developing infection had significantly lower percentages of CD27+ B cells and CD27- NK cells, as well as increased CD27-/CD27+ T-cell ratio in bone marrow. These immune risk factors were validated in three independent datasets. An immune score was developed to stratify patients with ≤1 vs ≥2 of the aforementioned risk factors, which was associated with higher infection incidence (35% vs 60%, P <.001). The immune score (odds ratio: 2.31, P <.001), disease stage and CD38, BCMA or GPRC5D targeted therapy were independently associated with infection incidence. All cell types detectable in bone marrow and peripheral blood were significantly correlated, suggesting that immune biomarkers of increased infection risk could be monitored using minimally-invasive methods that are available in routine laboratories.