Mycobacteria-induced secretion of cytokines and chemokines in healthcare workers with apparent resistance to infection with Mycobacterium tuberculosis.

Cytokines and chemokines in PBMC supernatants (stimulated with Mtb and BCG), plasma and supernatants from Quantiferon-TB PLUS assay (Nil and TB1 stimulated) after incubation for 16-20 hours. Concentrations were measured by Luminex using the ProcartaPlex Human Monitoring Panel 65-plex panel (Invitrogen™) according to manufacturers' instructions. Biological samples were collected from individuals with latent TB infection (LTBI, IGRA+ & TST+), people with resistance to Mtb infection (Resisters, IGRA- & TST-) and people with previous but successfully treated TB. IGRA+ for IFN-gamma level >0.35IU/mL; IGRA- for IFN-gamma 10mm and TST- for induration