Several studies have shown that heat shock protein (HSP)-reactive T cells have an immunoregulatory phenotype indicating that HSPs are able to trigger immunoregulatory pathways, which can suppress immune responses that occur in human inflammatory diseases, such as rheumatoid arthritis (RA). Mycobacterium bovis strain Bacillus Calmette-Guérin (BCG) is rich of HSPs which could be good resources of these regulatory proteins for modulation of immune response.
To study the effects of BCG-lysate and BCG-derived HSPs on secretion of T regulatory cytokines by PBMCs of RA patients in comparison with healthy controls.
BCG was heat killed and sonicated to have BCG-lysate. BCG-derived HSP65/HSP70 were detected by immunoblotting and purified by preparative SDS-PAGE. PBMCs of 18 RA patients/16 controls collected by Ficoll-paque were stimulated with BCG-lysate/BCG-derived HSP-65/HSP-70. Supernatant of stimulated PBMCs was aspirated for measuring TGF-beta, IL-10, IL-4 and IFN-gamma with sandwich ELISA.
BCG-lysate augmented the amounts of all the mentioned cytokines as dose dependent significantly. The level of TGF-beta in controls was higher than patients (P<0.05). HSP65 and HSP70 increased TGF-beta, IL-10 as dose dependent significantly. HSP65, but not HSP70, increased IL-4. HSP65 did not increase IFN-gamma but HSP70 augmented IFN-gamma significantly. BCG-lysate increased IFN-gamma and IL-4 in RA patients more than healthy controls (P<0.05).
Although BCG is able to provoke T helper 1 cell mediated immunity, its HSP proteins are able to trigger T regulatory cytokines. Healthy controls were under stronger immune regulations.