Hemocyte responses to implanted tissues inDrosophila melanogaster larvae

Area of Science:

• Developmental Biology
• Immunology
• Genetics

Background:

• Melanotic tumors in Drosophila melanogaster larvae are associated with temperature-sensitive mutations (tu-Sz ts).
• At permissive temperatures (26°C), tu-Sz ts larvae develop tumors from aberrant adipose tissue encapsulated by hemocytes (lamellocytes).
• At non-permissive temperatures (18°C), lamellocytes are present but tumors do not form.

Purpose of the Study:

• To investigate the mechanism by which low temperature prevents melanotic tumor formation in tu-Sz ts Drosophila larvae.
• To determine the discriminatory capabilities of lamellocytes in recognizing and encapsulating foreign or damaged tissues.

Main Methods:

• Culturing tu-Sz ts Drosophila larvae at different temperatures (18°C and 26°C).
• Implanting mechanically damaged and undamaged fat bodies and adipose cells into larvae.
• Challenging lamellocytes with heterospecific tissues from different Drosophila species.
• Utilizing ultrastructural examination to analyze encapsulated tissues.

Main Results:

• At 18°C, lamellocytes encapsulated mechanically damaged fat bodies and basement membrane-free adipose cells but not intact host fat bodies or implanted fat bodies with intact basement membranes.
• Low temperature normalizes prospective tumor-forming sites in tu-Sz ts larvae, preventing melanotic tumor development.
• Lamellocytes distinguished between tissues from sibling species (not encapsulated) and those from more distant species (encapsulated).
• Ultrastructural analysis revealed intact basement membranes in encapsulated heterospecific tissues, suggesting basement membrane architecture is key for self/non-self distinction.

Conclusions:

• Low temperature prevents melanotic tumor formation in tu-Sz ts larvae by normalizing the surface of adipose tissue.
• Drosophila lamellocytes discriminate between 'self' and 'non-self' based on the molecular architecture of the basement membrane.
• The continuous presence of lamellocytes is essential for the encapsulation process in larval hosts.