IL-7 in the cell-mediated immune response to a human pathogen

Area of Science:

• Immunology
• Infectious Diseases
• Molecular Biology

Background:

• Leprosy (caused by Mycobacterium leprae) presents a spectrum of immune responses.
• Clinical manifestations correlate with cell-mediated immunity levels.
• The role of Interleukin-7 (IL-7) in regulating these responses is not fully understood.

Purpose of the Study:

• To investigate the role of IL-7 in immune responses to Mycobacterium leprae infection.
• To determine if IL-7 is produced at the site of infection in leprosy.
• To assess the impact of IL-7 on cell-mediated immunity in different forms of leprosy.

Main Methods:

• Polymerase Chain Reaction (PCR) was used to measure IL-7 and IL-7 Receptor (IL-7R) mRNA in skin lesions.
• Cellular sources of IL-7 were identified.
• Peripheral Blood Mononuclear Cell (PBMC) responses to M. leprae were analyzed in the presence and absence of IL-7.

Main Results:

• IL-7 mRNA expression was significantly higher in tuberculoid leprosy lesions (limited infection) compared to lepromatous lesions (progressive infection).
• IL-7R mRNA expression also showed higher levels in tuberculoid lesions.
• Ag-stimulated monocytes and IFN-gamma-induced keratinocytes were identified as cellular sources of IL-7.
• M. leprae induced IL-7 and IL-7R mRNA in tuberculoid patients' PBMCs, with T cell responses being IL-7 dependent.
• M. leprae did not induce IL-7 mRNA in lepromatous patients, and their T cell responses showed only weak augmentation by recombinant IL-7 (rIL-7).

Conclusions:

• IL-7 is produced at the site of leprosy infection.
• IL-7 plays a significant role in supporting the cell-mediated immune response against Mycobacterium leprae.
• These findings highlight IL-7's contribution to controlling human infections.