Secretion of cytokines, chemokines and antibodies in individuals with resistance to Mycobacterium tuberculosis infection
Cytokines and total antibodies in plasma and supernatants from Quantiferon-TB PLUS assay (Nil and TB1 stimulated) after inclubation for 16-20 hours. Concentrations were measured using luminex assays kits from Biorad (antibody isotyping panel) and Merck-Melliplex (high sensitivity T cell panel) according to manufacturers' instructions.
Samples were collected from individuals with latent TB infection (LTBI, IGRA+ & TST+), people with resistance to Mtb infection (Resisters, IGRA- & TST-) and people with discordant results for IGRA and TST (TST=0 and IGRA > 1IU/mL). IGRA+ for IFN-gamma level >0.35IU/mL; IGRA- for IFN-gamma <0.35IU/mL; TST+ for induration >10mm and TST- for induration <10mm