Antigen presentation in protein-energy malnutrition

Area of Science:

• Immunology
• Nutrition Science
• Cellular Biology

Background:

• Protein-energy malnutrition (PEM) is known to cause intrinsic defects in macrophage microbicidal function.
• The impact of PEM on macrophage-CD4+ cell interactions, specifically antigen presentation (AP), remains unclear.
• Prostaglandin (PGE2) and nitric oxide (NO) are potential regulatory mechanisms in immune interactions.

Purpose of the Study:

• To investigate the effect of PEM on AP components by peritoneal macrophages (PMO) and splenocyte responses (MLR).
• To assess the role of PGE2 and NO in modulating these immune interactions in both naive and Mycobacterium-BCG infected states.
• To evaluate the impact of specific inhibitors (NMMA for NO, indomethacin for PGE2) on AP and MLR.

Main Methods:

• Mice were fed either a control (24% casein) or low-protein (2.5% casein) diet for 8 weeks.
• Peritoneal macrophages (PMO) and splenocytes were harvested for assessment of AP function and MLR.
• Inhibitors of NO synthesis (NMMA) and PGE2 synthesis (indomethacin) were used to evaluate their effects.

Main Results:

• Antigen presentation (AP) and mixed lymphocyte reaction (MLR) were preserved in protein-energy malnutrition (PEM) groups.
• BCG infection in control diet mice impaired AP and MLR, an effect reversed by NMMA and indomethacin.
• PEM groups showed defective phagocytosis, IL-1, IL-6 production, and reduced NO and PGE2 synthesis.

Conclusions:

• Despite defects in individual PMO components, AP and MLR were preserved in low-protein diet (LPD) mice.
• This preservation may be attributed to a loss of prostaglandin- and L-arginine-mediated suppressor mechanisms in PEM.
• PEM alters immune regulation, potentially preserving cellular interactions despite functional deficits.