In vitro expansion of CD3⁻, CD172a⁺ cells within PBMC cultures from <i>M. bovis</i> infected cattle stimulated with ESAT-6/CFP-10.

aData are presented as mean (±standard error) percent of CD3−, CD172a+, PKH67lo cells (R2 gate in Fig. 1A). Isolated mononuclear cells were stained with PKH67 (a green fluorescent dye used for cell proliferation analysis), cultured for 6 days with or without stimulation as indicated in the upper margin, and analyzed by flow cytometry for phenotype and PKH67 staining intensity. Both BCG and ΔRD-1 attenuated M. bovis vaccine strains lack ESAT-6, CFP-10, and select ESX-1 secretion apparatus genes; thus, these strains do not produce ESAT-6 or CFP-10. In contrast to ESAT-6/CFP10, stimulation with MPB83, another immunodominant antigen of M. bovis, does not result in expansion of CD172a+ cells.