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Decrease of three lysosomal enzymes in guinea pig macrophages activated by lymphocyte mediators

H G Remold1, A Mednis

  • 1Departments of Medicine and Biological Chemistry, Harvard Medical School and Robert B. Brigham Hospital, Boston, Massachusetts.

Inflammation
|November 7, 2013
PubMed

Insights

Activated guinea pig macrophages showed reduced lysosomal enzyme activity and phagocytosis. Lymphocyte activation also did not increase these macrophage defense mechanisms, challenging prior assumptions.

Area of Science:

  • Immunology
  • Cell Biology

Background:

  • Macrophage activation is crucial for immune responses.
  • Lysosomal enzymes and phagocytosis are key macrophage functions.

Purpose of the Study:

  • To investigate the effect of macrophage-activating factors (MAFs) on lysosomal enzyme activity and phagocytosis in guinea pig macrophages.
  • To determine if lymphocyte-derived mediators enhance macrophage defense mechanisms.

Main Methods:

  • Guinea pig peritoneal macrophages were incubated with MIF-rich medium for 72 hours.
  • Lysosomal enzyme activity (acid phosphatase, β-glucuronidase, cathepsin D) and phagocytosis of denatured hemoglobin were measured.
  • Macrophages were also activated by sensitized and stimulated lymphocytes.

Main Results:

  • Incubation with MIF-rich medium led to decreased specific activity of lysosomal enzymes and reduced phagocytosis.
  • Enhanced enzyme release into the supernatant did not explain the decreased intracellular activity.
  • Activation by lymphocytes resulted in unchanged or decreased lysosomal enzyme activity.

Conclusions:

  • Macrophage activation by MIF-rich medium or lymphocyte mediators does not enhance lysosomal enzyme activity.
  • Decreased lysosomal enzyme activity and phagocytosis suggest a complex regulatory mechanism during macrophage activation.
  • The findings challenge the notion that increased lysosomal enzyme activity is a primary component of lymphocyte-mediated macrophage defense.

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