Intravital microscopy of the peripheral lymph node microcirculation in mice

Area of Science:

• Immunology
• Microcirculation Research
• Cell Biology

Background:

• Lymphocyte homing to lymph nodes is crucial for adaptive immunity.
• L-selectin (CD62L) and peripheral node addressin (PNAd) are critical for lymphocyte trafficking.
• Understanding these interactions requires advanced in vivo visualization techniques.

Purpose of the Study:

• To develop a novel intravital microscopy model for observing murine peripheral lymph node microcirculation.
• To characterize the functional role of L-selectin and PNAd in lymphocyte adhesion.
• To analyze the molecular mechanisms of lymphocyte homing to high endothelial venules (HEV).

Main Methods:

• Microsurgical dissection of murine subiliac lymph nodes.
• Intravital video microscopy to analyze microvascular architecture and hemodynamics.
• Fluorescently labeled L1-2 cells (transfected with or without L-selectin) were injected to study adhesion in venules, with and without blocking antibodies.

Main Results:

• The developed model enabled detailed analysis of leukocyte adhesion in lymph node microvessels.
• L-selectin-expressing cells exhibited rolling primarily in subcortical HEV and downstream venules.
• Rolling interactions were significantly reduced by antibodies targeting L-selectin and PNAd.

Conclusions:

• A new intravital microscopy model for visualizing leukocyte-lymph vessel interactions in murine lymph nodes was established.
• The study confirms L-selectin and PNAd as the primary receptor-ligand pair mediating lymphocyte rolling in HEV.
• This model offers a valuable tool for high-resolution analysis of events within living lymph nodes.