Abstract
The lack of efficient tools for identifying immunological correlates of tuberculosis (TB) protection or risk of disease progression impedes the development of improved control strategies. To more clearly understand the host response in TB, we recently established an imaging flow cytometer-based in-vitro assay, which assesses multiple aspects of T cell-monocyte interaction. Here, we extended our previous work and characterized communication between T cells and monocytes using clinical samples from individuals with different TB infection status and healthy controls from a TB endemic setting. To identify T cell-monocyte conjugates, peripheral blood mononuclear cells (PBMC) were stimulated with ds-Red-expressing Mycobacterium bovis bacille Calmette-Guérin or 6-kDa early secreted antigenic target (ESAT 6) peptides for 6 h, and analyzed by imaging flow cytometer (IFC). We then enumerated T cell-monocyte conjugates using polarization of T cell receptor (TCR) and F-actin as markers for synapse formation, and nuclear factor kappa B (NF-κB) nuclear translocation in the T cells. We observed a reduced frequency of T cell-monocyte conjugates in cells from patients with active pulmonary tuberculosis (pTB) compared to latent TB-infected (LTBI) and healthy controls. When we monitored NF-κB nuclear translocation in T cells interacting with monocytes, the proportion of responding cells was significantly higher in active pTB compared with LTBI and controls. Overall, these data underscore the need to consider multiple immunological parameters against TB, where IFC could be a valuable tool.