Optimizing usage of remaining blood from Interferon Gamma Releasing Assay (IGRA) to search for immune signatures and biomarkers for Latent Tuberculosis Infection (LTBI)

of T cell activation molecules IFN-g production in response to QTF We immunophenotyped the remaining blood cells used in the QTF test. Our preliminary results show that, as expected, most of the cells present in the lymphocyte gate are CD45+/CD3+ with a median of 77.8% (Tube N, Nill); 82.5% (Mitogen, M); 74.03% (TB1) and 76.75% (TB2). Considering CD4+ T cells, we detected 56% (N), 44% (M), 56% (TB1) and 55% (TB2). On the other hand, we showed that there were 28% (N), 25% (M), 31% (TB1) and 29% (TB2) of CD8+ T cells in the tubes. When we looked for activation markers (CD69, CD71 and HLA-DR) we showed that when T cells are stimulated with mitogen there are higher percentages of T cells, TCD4+ TCD8+ expressing these markers. For the antigen-specific tubes (TB1 and TB2) there were not enough QTF positive samples to conclude the correlation of IFN-g production with the expression of these activation markers. Conclusion: We conclude that it is possible to better characterize the immune phenotype of remaining blood from IGRA.