Mycobacterium tuberculosis induces CCL18 expression in human macrophages

Area of Science:

• Immunology
• Microbiology

Background:

• Mycobacterium tuberculosis (MTB) interaction with the immune system involves cytokine and chemokine responses.
• Chemokine (C-C motif) ligand 18 (CCL18) and Interleukin-10 (IL-10) are key secreted factors.
• These factors are postulated to recruit naive T lymphocytes and inhibit pro-inflammatory responses.

Purpose of the Study:

• To investigate the role of CCL18 and IL-10 in an in vitro model of MTB infection in human macrophages.

Main Methods:

• Human CD14(+) monocytes were differentiated into monocyte-derived macrophages (MDM).
• MDM and alveolar macrophages were stimulated with lipopolysaccharide (LPS) and heat-killed MTB.
• CCL18 protein and mRNA levels were measured by ELISA and real-time PCR, IL-10 by ELISA.

Main Results:

• MTB stimulation significantly increased CCL18 protein and mRNA levels in MDM.
• Infected alveolar macrophages showed increased CCL18 production.
• IL-10 levels were significantly elevated in LPS- and MTB-stimulated cells.

Conclusions:

• Up-regulation of CCL18 and IL-10 in macrophages by MTB suggests involvement in naive T cell recruitment.
• This may contribute to local suppressive immunity against intracellular pathogens.
• This mechanism could facilitate immune tolerance during early MTB infection phases.