Toll-like receptor 2 (TLR2) is critical in the immune response to mycobacterial infections. The purpose of this study was to analyze TLR2 surface expressions and TLR2-mediated tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) production in patients with BCG vaccine-associated suppurative lymphadenitis.

Peripheral monocytes were separated from 16 patients with BCG vaccine-associated suppurative lymphadenitis and 10 healthy controls using a magnet cell isolation kit. Monocytes (1×10⁶ cells/well) were incubated with a constant amount of Pam₃CSK₄ (100 µg/mL) for 24 hours. TLR2 surface expression on monocytes was analyzed by FACS analysis and TLR-2 mRNA expression was determined by RT-PCR. TLR2-mediated TNF-α and IL-6 production were measured by ELISA.

In patients with BCG vaccine-associated suppurative lymphadenitis, low TLR2 expression on monocytes (3.39±1.2% versus 4.64±2.6%) together with significantly lower TLR2 mRNA expression than in the healthy controls was seen after Pam₃CSK₄ stimulation. TLR2-mediated TNF-α and IL-6 production in patients with BCG vaccine-associated suppurative lymphadenitis (TNF-α, 775.5±60.8 pg/mL; IL-6, 4,645.8±583.9 pg/mL) were also lesser than that in healthy controls (TNF-α, 1,098.5±94.3 pg/mL; IL-6, 6,696.3±544.3 pg/mL).

These findings suggest that low TLR2 expression on monocytes might be associated with increased susceptibility to BCG vaccine-associated suppurative lymphadenitis.