Stimulation of neutrophil granulocytes with Mycobacterium bovis bacillus Calmette-Guérin induces changes in phenotype and gene expression and inhibits spontaneous apoptosis

Abstract

Polymorphonuclear neutrophil granulocytes (PMN) have been implicated in the early inflammatory response against mycobacteria besides monocytes/macrophages. Yet, little is known about the interaction of mycobacteria with PMN. We investigated the potential of Mycobacterium bovis bacillus Calmette-Guérin (BCG) to stimulate and influence PMN phenotype, gene expression profile and spontaneous apoptosis. Flow cytometric analyses revealed an upregulation of the function-associated molecules Fcγ receptor III (FcγR III) and II (CD16 and CD32) as well as MAC-1 (CD11b and CD18) on BCG-stimulated PMN. As determined by cDNA microarrays and multiplex reverse transcriptase PCR, stimulation with BCG alters the expression of various genes for proinflammatory cytokines/chemokines or receptors in PMN. We detected an upregulation or de novo synthesis of interleukin 1α (IL-1α), IL-1β, IL-8, macrophage inflammatory protein 1α (MIP-1α), MIP-1β, GRO-α, transforming growth factor β, MCP-1, IL-2 receptor γ (IL-2Rγ), IL-10Rα, and IL-6R. Genes for IL-9, IL-12α, IL-15, 1L-5Rα, and IL-13Rα1 were found to be downregulated or switched off. Furthermore, Giemsa and annexin V-propidium iodide double staining demonstrated an inhibition of spontaneous PMN apoptosis following BCG stimulation. Changes in phenotype and inhibition of apoptosis did not depend on direct mycobacterial stimulation alone, but were a result of an autocrine-paracrine stimulation mechanism. Our findings support the hypothesis that PMN become activated at the site of mycobacterial infections and that this activation might set the stage for a subsequent antimycobacterial immune response.