Amigo2 and Cd44 functions in the development of B-cell-mediated immune responses

• Applicant: Dr. Lesly Calderon
• Subject Area: Immunology
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 570624963

B cell responses are essential for humoral immunity against pathogens, as they lead to the generation of antibody-secreting cells that produce large amounts of antigen-specific antibodies to eliminate the infection. B-cell responses also give rise to long-lived memory B cells; similarly, antibody-secreting cells have the potential to become quiescent and long-lived. Both cell types are fundamental to immunological memory against pathogens. Misguided B-cell responses can also mediate diseases, such as allergies, antibody-mediated autoimmunity, and malignancies. To identify new regulators of B cell activation and antibody-secreting cell development in the context of the splenic microenvironment, we established an in vivo model system for pooled sgRNA CRISPR/Cas9 screens in mice immunized with model antigens. Using this in vivo system, we identified several novel positive and negative regulators of B-cell activation, antibody-secreting cell differentiation, and homeostasis that were not identified in previous in vitro screens. Two notable regulators are the adhesion molecules Amigo2 (positive regulator) and Cd44 (negative regulator). Our project aims to study the functions of Amigo2 and Cd44 in the development of B cell-mediated immune responses. Using novel experimental approaches, along with in vitro and in vivo mouse models, we will explore the molecular mechanisms underlying the function of Amigo2 and Cd44. The research will be conducted with the following objectives: 1. To determine the effects of Amigo2 and Cd44 gene deletion on the generation and homeostasis of antibody-secreting cells. 2. To determine the processes and signalling pathways regulated by Amigo2 and Cd44, which are important for the development of B-cell responses. Part 1 of this proposal assesses defects in Amigo2- and Cd44-deficient B cells in vivo at a steady state or after antigen immunization. Together with in vitro B cell activation assays, these experiments will pinpoint the stages during the generation of B cell responses that might be primarily affected by Amigo2- and Cd44-inactivation. Part 2 of the proposal outlines transcriptomic, proteomic, and phosphoproteomic experiments that investigate the signalling pathways affected in Amigo2- and Cd44-deficient B cells upon activation and differentiation into antibody-secreting cells. Our research will offer new insights into the molecular mechanisms that regulate B-cell activation and differentiation into effector B-cells. Furthermore, it may reveal previously unidentified molecular pathways that govern B-cell-mediated immune responses. These novel pathways may offer opportunities for therapeutic intervention to boost immunity against pathogens or to control B-cell function under various conditions, including autoimmune disorders, allergies, and B-cell malignancies.

• DFG Programme: Research Grants