Cell surface changes of in situ macrophages induced by superimposed antigen

Area of Science:

• Immunology
• Cell Biology
• Histology

Background:

• Macrophages play a crucial role in immune responses.
• The protein-bound polysaccharide from Coriolus versicolor (PSK) is known to modulate immune activity.
• Understanding macrophage behavior is key to developing immunotherapies.

Purpose of the Study:

• To investigate the ultrastructural changes in macrophages after stimulation with sheep erythrocytes (SRBC).
• To examine the effect of pre-treatment with PSK on macrophage morphology and interaction.
• To elucidate the role of PSK in preparing the local immune environment for enhanced responses.

Main Methods:

• Mice were injected with SRBC into the footpad, with or without prior PSK administration.
• In situ macrophages were studied using electron microscopy at various time points post-injection.
• Morphological alterations and intercellular interactions of macrophages were analyzed.

Main Results:

• SRBC injection alone induced linear arrangements of macrophages without significant morphological changes.
• PSK-stimulated macrophages exhibited rapid extension of numerous cytoplasmic projections upon SRBC challenge.
• These projections interlocked, forming large aggregations of activated macrophages, suggesting intercellular communication.

Conclusions:

• PSK pre-treatment enhances macrophage activation and promotes intercellular communication via cytoplasmic projections.
• This PSK-induced macrophage activation in the subcutaneous tissue supports a splenic humoral immune response.
• The findings provide histological evidence for PSK's role in modulating local immune environments for improved immune surveillance.