PURPOSE: In this study we investigated the molecular basis of the hierarchy of CXCR3 over CCR5 and CD11a in T cell recruitment to the disease site among tuberculosis pleural effusion patients.
METHODS: Using standard three color flow cytometry, we studied simultaneous expression of these three homing receptors at single cell level on the T cells obtained from tuberculosis (TB) pleural effusion.
RESULTS: We compared the frequencies of T cells in the peripheral blood and Pleural fluid in 15 patients.We observed a significant enrichment of CXCR3 CCR5 dual positive T cells in the pleural fluid as compared with the peripheral blood. It was also noted that CXCR3+ CD11a bright and CCR5+ CD11a bright cells were over-represented at the local disease site. It was interesting to note that all CCR5 or CD11a single positive cells were invariably positive for CXCR3 but all CXCR3 positive cells didn’t co-express either CCR5 or CD11a. To observe selective migration of these CXCR3+ and CCR5+ T cells, we performed in vitro chemotaxis experiment using transwell chamber and HUVEC monolayer in 8 patients. A four fold increase in migration of the T cells was observed by using Regulated Upon Activation T Cell Expressed and Secreted (RANTES) as a chemoattractant as compared with the controls, followed by Interferon Gamma Inducible Protein (IP10). In chemotaxis assay experiments major proportion of migrated cells was dual positive for CXCR3 and CCR5 T cells. In response to Mtb Mycobacterium tuberculosis) antigen, IFN γ producing cells were found to be significantly higher at the local site as compared with the peripheral blood.
CONCLUSION: Our data demonstrate hierarchical role of CXCR3+ T cells and crucial role of above mention chemokines in selective recruitment of Th1 like cells in TB pleural effusion.
CLINICAL IMPLICATIONS: The precise mechanism of positioning of these T cells are still unclear.However the precise control of migration appears to be mediated by certain chemokine receptors and chemokines.Intervention into these molecular events may lead to future therapeutic modalities.
DISCLOSURE: Pradip Saha, None.