Drosophila larval fat body surfaces : Changes in transplant compatibility during development

Area of Science:

• Developmental biology
• Immunology
• Cell biology

Background:

• Drosophila melanogaster hemocytes exhibit selective immune responses, encapsulating foreign or modified tissues but not unmodified self-tissues.
• Larval fat body surfaces undergo developmental changes influencing their recognition by the host immune system.

Purpose of the Study:

• To investigate changes in Drosophila melanogaster larval fat body surfaces during development.
• To determine the cues that trigger hemocyte encapsulation of fat body tissues.

Main Methods:

• Assaying fat body acceptance or rejection by tu-Sz ts hosts at different larval developmental stages.
• Examining fat body surface ultrastructure using electron microscopy.
• Treating fat bodies with fluorescein isothiocyanate-conjugated lectins to probe surface carbohydrates.
• Reacting fat body surfaces with a monoclonal antibody specific for basement membrane.

Main Results:

• Fat bodies from early larval stages were accepted, while those from spiracle eversion onwards were rejected by tu-Sz ts hosts.
• Ultrastructural examination and lectin binding did not reveal surface changes correlating with rejection.
• A monoclonal antibody against basement membrane failed to bind to D. virilis fat body, which is consistently rejected.

Conclusions:

• Hemocyte recognition of fat body surfaces involves cues beyond gross morphological changes or detectable ultrastructural/lectin-binding alterations.
• The molecular architecture of the basement membrane is likely a critical factor in initiating the hemocyte encapsulation response in Drosophila.