Characterization of a lymphocyte factor which alters macrophage functions

Area of Science:

• Immunology
• Cell Biology

Background:

• Lymphocytes release soluble factors that modulate macrophage activity.
• Previous work identified a factor activating macrophages, increasing adherence, spreading, phagocytosis, and glucose oxidation.

Purpose of the Study:

• Characterize the activating factor's properties and kinetics.
• Determine if the activating factor is distinct from other known lymphocyte mediators.
• Investigate the temporal stages of macrophage activation.

Main Methods:

• Sephadex G-100 gel filtration
• CsCl density gradient centrifugation
• Neuraminidase sensitivity assays
• Kinetic studies of macrophage activation

Main Results:

• The activating factor was indistinguishable from migration inhibitory factor (MIF) via gel filtration, density gradients, and enzyme sensitivity.
• The activating factor is distinct from chemotactic factor and lymphotoxin.
• Macrophage activation occurs in two stages over 3 days: an initial refractory period followed by responsiveness.
• Activated macrophage effects persist for 24 hours without the factor.
• Macrophage response kinetics are consistent in purified and unfractionated supernatants.

Conclusions:

• The macrophage activating factor is identical to MIF.
• In vitro, macrophages exhibit migration inhibition before becoming sensitive to MIF's activating effects.