Ultrastructure of leprous phlebitis.

Area of Science:

• Vascular Biology
• Infectious Diseases
• Microbiology

Background:

• Leprosy is a chronic infectious disease caused by Mycobacterium leprae.
• The precise mechanisms of Mycobacterium leprae dissemination and cellular tropism within the host remain incompletely understood.
• Ultrastructural studies are crucial for elucidating cellular interactions in infectious diseases.

Purpose of the Study:

• To investigate the ultrastructural characteristics of Mycobacterium leprae within vein biopsies of lepromatous leprosy patients.
• To determine the cellular origin and release mechanisms of Mycobacterium leprae from endothelial cells.
• To assess the interaction and potential replication of Mycobacterium leprae within endothelial and smooth muscle cells.

Main Methods:

• Ultrastructural analysis of vein biopsies from six lepromatous leprosy patients.
• Transmission electron microscopy to identify cellular structures and Mycobacterium leprae.
• Characterization of endothelial cell markers, such as Weibel-Palade granules.

Main Results:

• Lumen-lining cells in vein biopsies were identified as endothelial cells, confirmed by the presence of Weibel-Palade granules.
• Endothelial cells were observed releasing Mycobacterium leprae into the vascular lumen via exophagocytosis.
• Mycobacterium leprae demonstrated the capacity for growth and multiplication within both endothelial and smooth muscle cells.
• Smooth muscle cells did not exhibit signs of cellular reaction despite the intracellular presence of Mycobacterium leprae.

Conclusions:

• Endothelial cells play a significant role in the release of Mycobacterium leprae into the bloodstream.
• Mycobacterium leprae can infect and replicate within endothelial and smooth muscle cells, suggesting these cells as potential reservoirs.
• The lack of reaction in smooth muscle cells warrants further investigation into immune evasion strategies of Mycobacterium leprae.