Diminished Frequencies of Cytotoxic Marker Expressing T- and NK Cells at the Site of Mycobacterium tuberculosis Infection.

Tuberculous lymphadenitis (TBL) individuals exhibit reduced frequencies of CD8 ⁺ T cells expressing cytotoxic markers in peripheral blood. However, the frequencies of cytotoxic marker expressing CD4 ⁺ , CD8 ⁺ T cells, and NK cells at the site of infection is not known. Therefore, we measured the baseline and mycobacterial antigen specific frequencies of cytotoxic markers expressing CD4 ⁺ , CD8 ⁺ T cells, and NK cells in the LN ( n = 18) and whole blood ( n = 10) of TBL individuals. TBL LN is associated with lower frequencies of CD4 ⁺ T cells expressing cytotoxic markers (Granzyme B, CD107a) compared to peripheral blood at baseline and in response to PPD, ESAT-6, and CFP-10 antigen stimulation. Similarly, lower frequencies of CD8 ⁺ T cells expressing cytotoxic markers (Perforin, Granzyme B, and CD107a) were also present in the TBL LN at baseline and following (except perforin) antigen stimulation. Finally, at baseline and after antigen (PPD, ESAT-6, and CFP-10) stimulation, frequencies of NK cells expressing cytotoxic markers were also significantly lower in TBL LN compared to whole blood. Hence, TBL is characterized by diminished frequencies of cytotoxic marker expressing CD4 ⁺ , CD8 ⁺ T cells, and NK cells at the site of infection, which might reflect the lack of protective immune responses at the site of Mycobacterium tuberculosis infection.
(Copyright © 2020 Kathamuthu, Moideen, Sridhar, Baskaran and Babu.)