CD40-CD40 Ligand Interactions in the Production of IL-12 and IFN-gamma by Tuberculous Pleural Mononuclear Cells

ABSTRACT

BACKGROUND: Our previous study showed that purified protein derivative (PPD)- stimulated pleural mononuclear cells (PMC) from tuberculous pleurisy (Tbp) produced significantly more IFN-gamma (10- to 70-fold) after in vitro PPD stimulation than freshly isolated pleural cells from malignant pleurisy. The present study was designed to determine whether blocking the CD40-CD40 ligand (CD40L) interaction decreases IFN-gamma production by altering IL-12 levels. METHODS: IL-12 and IFN-gamma production after neutralizing anti-CD40L antibody treatment was compared to the efficacy of anti-CD80, anti-CD86, and a combination of anti-CD80 and CD86 (CD80+86) monoclonal antibodies (mAb). These activities were measured by enzyme-linked immunosorbent assays (ELISAs) and reverse transcription-polymerase chain reaction (RT-PCR), after in vitro stimulation with PPD antigen (Ag). RESULTS: Neutralization of CD80, CD86 and CD80+86 did not decrease IFN-gamma and IL-12 production in Tbp-PMC, whereas neutralization of CD40L significantly depressed IL-12 p40 and IFN-gamma. In addition, neutralization of CD40L completely inhibited IL-12 p40 and IFN-gamma mRNA expression. CONCLUSION: The CD40-CD40L interaction might play a major role in IL-12 and IFN-gamma production in Tbp-PMC, thus contributing to protective immunity in human tuberculosis.