TB Antigen-Stimulated CXCR3 Ligand Assay for Diagnosis of Tuberculous Lymphadenitis

Mycobacterium tuberculosis-specific memory T cells in bronchoalveolar lavage of patients with pulmonary tuberculosis

BACKGROUND

Mycobacterium tuberculosis(MTB) most often infects the lungs and results in pulmonary tuberculosis(TB). MTB-specific memory T cells are able to respond quickly against antigens and help reduce the burden of pulmonary bacteria. The characteristics, function and chemotaxis axis of memory T cells in the lung remain unclear. The current study aimed to clarify the classification, function and recruitment of local antigen-specific memory T cells in the lung and the periphery blood of patients with pulmonary TB.

METHODS

A total of 85 patients with active pulmonary TB were included in the study. Bronchoalveolar lavage fluid (BALF) and Peripheral blood were collected for further detection. The cell-surface markers and intracellular staining of memory T cell subtypes were measured by flow cytometry. The level of CXCL9, CXCL10 and CXCL11 in Bronchoalveolar lavage fluid cells and peripheral blood mononuclear cells (PBMC) were measured by Real-time PCR.

RESULTS

The ratio of effective Memory T cells (TEM) were the highest in BALF of patients with pulmonary TB. In patients, CXCR3 and its ligands was increased in memory T cells of BALF compared with PBMC. IFN-γ+TNF-α+ effective Memory T cells and central memory T cells from BALF were increased after antigen stimulation. CXCR3 was higher in IFN-γ+ compared with IFN-γ- in CD4+ TCM and TEM from BALF of patients. Compared with PBMC, the PD-1 levels of terminal effector memory RA+(TEMRA) and TEM cells in CD4+ memory T cells of BALF were significantly increased. In addition, PD-1 was increased in IFN-γ+ compared with IFN-γ- in CD4+TEM from BALF of patients. There was no difference in Treg ratio between PBMC and BALF of TB patients.

CONCLUSIONS

The CXCL9/CXCL11-CXCR3 axis may participate in the chemotaxis of memory T cells from the peripheral to lung. CD4+TEM and TEMRA in BALF may have exhausted, especially the cytokine producing TEM. Our study clarified the characteristics of antigen-specific memory T cells in local lung and may have impact on strategies of therapy and vaccine.

Enhancing the interferon-γ release assay through omission of nil and mitogen values

PURPOSE

To address the limited utility of the interferon (IFN)-γ release assay (IGRA) caused by its variability and inconsistency.

METHODS

This retrospective cohort study was based on data obtained between 2011 and 2019. QuantiFERON-TB Gold-In-Tube was used to measure IFN-γ levels in nil, tuberculosis (TB) antigen, and mitogen tubes.

RESULTS

Of 9,378 cases, 431 had active TB. The non-TB group comprised 1,513 IGRA-positive, 7,202 IGRA-negative, and 232 IGRA-indeterminate cases. Nil-tube IFN-γ levels were significantly higher in the active TB group (median = 0.18 IU/mL; interquartile range: 0.09-0.45 IU/mL) than in the IGRA-positive non-TB (0.11 IU/mL; 0.06-0.23 IU/mL) and IGRA-negative non-TB (0.09 IU/mL; 0.05-0.15 IU/mL) groups (P < 0.0001). From receiver operating characteristic analysis, TB antigen tube IFN-γ levels had higher diagnostic utility for active TB than TB antigen minus nil values. In a logistic regression analysis, active TB was the main driver of higher nil values. In the active TB group, after reclassifying the results based on a TB antigen tube IFN-γ level of 0.48 IU/mL, 14/36 cases with negative results and 15/19 cases with indeterminate results became positive, while 1/376 cases with positive results became negative. Overall, the sensitivity for detecting active TB improved from 87.2 to 93.7%.

CONCLUSION

The results of our comprehensive assessment can aid in IGRA interpretation. Since nil values are governed by TB infection rather than reflecting background noise, TB antigen tube IFN-γ levels should be used without subtracting nil values. Despite indeterminate results, TB antigen tube IFN-γ levels can be informative.