Bone marrow free immune checkpoints as a potential biomarker for differential diagnosis of acquired bone marrow failures

OBJECTIVE: Clinically, to make a definite diagnosis of aplastic anemia (AA), idiopathic cytopenia of undetermined significance (ICUS) or myelodysplastic syndrome (MDS), they should be distinguished from each other. AA and ICUS have some incidence to transform into MDS. Immunosuppressive therapy (IST) is effective in AA and partial ICUS patients, while other ICUSs are more likely to progress to MDS without response to IST. To date, we neither found a technical method that could easily identify AA from hypoproliferative MDS, nor a simple parameter that could indicate ICUS with a response to IST. Here, we detected the concentration of free immune checkpoints in bone marrow supernatant of AA, ICUS, and MDS patients, analyzed the differences of immune status among these three diseases, to try to find a way to predict the response to IST in ICUSs. METHODS: Seventy‐four novel patients were enrolled with newly diagnosed acquired bone marrow failure (including 29 AA patients, 11 ICUS patients, and 34 MDS patients), bone marrow supernatants were collected. Luminex liquid suspension array technology was used to measure the concentrations of 17 immune checkpoints to analyze the differences of immune status among these three diseases. RESULTS: The levels of 17 free immune checkpoints were elevated in MDS and showed a strong correlation with each other, followed by ICUS, and with the weakest in AA. By drawing the ROC curve, we found eight immune checkpoints, including sCD40, sCD86/B7‐2, sCTLA‐4, sGITR, sHVEM, sPD‐1, sTIM‐3, and sTLR‐2, could easily distinguish AA from hypoproliferative MDS. ICUSs with lower concentrations of these eight free immune checkpoints predicted a better IST response. CONCLUSION: In conclusion, we found that there were notable differences in the immune status of AA, ICUS, and MDS. The concentrations of sCD40, sCD86/B7‐2, sCTLA‐4, sGITR, sHVEM, sPD‐1, sTIM‐3, and sTLR‐2 could be used to identify AA and hypoproliferative MDS patients, as well as to distinguish ICUS patients who could benefit from IST.