(186) Comparative Intravital Imaging of C-kit Expression and Its Co-localization with a C-kit–Targeting Antibody in Balb/c and Humanized hIgE/hFcεRI Mice

Introduction/Rationale: Mast cells are central regulators of immune responses and play a crucial role in allergic diseases and mastocytosis. Their functional response to IgE-dependent stimulation is strongly affected by the surface expression of the high-affinity IgE receptor (FcεRI). The interaction between FcεRI and c-Kit, another key mast cell marker, is essential for their survival, maturation, and activation. Understanding how these molecules are expressed and interact in vivo is therefore critical for evaluating immune mechanisms and antibody-based therapies.
This study aimed to compare the in vivo expression pattern of c-Kit and its co-localization with a c-Kit–targeting antibody between Balb/c mice and humanized hIgE/hFcεRI mice, providing insights into differential antibody–receptor interactions under physiological conditions.

Methods: Using intravital microscopy, we continuously monitored c-Kit expression and antibody localization in the lung tissue of both mouse models for up to three days under live conditions.

Results: c-Kit was found to be expressed on the surface of lung epithelial cells in both groups. Following antibody drug administration, co-localization between the antibody and c-Kit expression was prominently observed, particularly one day post-treatment in hIgE/hFcεRI mice. The extent of co-localization differed significantly between models: humanized mice exhibited markedly higher antibody–c-Kit overlap, whereas Balb/c mice showed relatively weak co-localization.

Conclusion: These findings highlight that intravital microscopy enables direct and longitudinal visualization of antibody drug–related immune responses in living animals. The combined analysis of hFcεRI and c-Kit expression provides a valuable in vivo indicator for assessing mast cell activity, development, and therapeutic responsiveness. This underscores the unique capability of intravital imaging to bridge molecular-level interactions with physiological immune responses in real time.