Phenotypic Approaches to Identify Inhibitors of B Cell Activation

Area of Science:

• Immunology
• Cell Biology
• Pharmacology

Background:

• B cell activation is crucial in immune responses and diseases like non-Hodgkin's lymphoma.
• Understanding B cell receptor (BCR) and CD40R signaling is key for developing targeted therapies.
• Existing assays may not fully capture the complexities of B cell activation pathways.

Purpose of the Study:

• To develop and validate a novel label-free phenotypic platform (EPIC) for assessing B cell activation.
• To investigate B cell activation mediated by BCR and CD40R signaling.
• To compare the EPIC assay with a FLIPR-based assay for B cell activation measurement.

Main Methods:

• Utilized an EPIC label-free phenotypic platform to measure the association of RL non-Hodgkin's lymphoma B cells with ICAM-1 coated plates.
• Stimulated B cells using anti-immunoglobulin M (anti-IgM) for BCR activation and mega CD40 Ligand (CD40L) for CD40R activation.
• Employed Bruton's tyrosine kinase (BTK) inhibitors and LFA-1/ICAM-1 specific inhibitors to assess pathway involvement.
• Established a FLIPR-based assay to measure calcium flux in response to B cell activation.

Main Results:

• The EPIC assay detected BCR activation via anti-IgM, which was inhibited by LFA-1/ICAM-1 and BTK inhibitors.
• Co-application of anti-IgM and CD40L enhanced LFA-1/ICAM-1 association compared to individual applications.
• Both anti-IgM and CD40L stimulation showed distinct kinetic profiles, inhibited by BTK inhibitors.
• The FLIPR assay showed calcium responses for BCR activation but not for CD40R activation.

Conclusions:

• The EPIC assay is a sensitive tool for evaluating B cell activation through both BCR and CD40R pathways.
• EPIC assay demonstrates potential for identifying novel inhibitors and understanding mechanisms of B cell activation inhibition.
• Compared to FLIPR, EPIC offers a broader scope for drug discovery targeting B cell malignancies and autoimmune diseases.