An independent study carried out at a Cellular Technology Ltd. cites using HemaCare PBMCs in their efforts to replicate physiological B cell activation in an assay format. 
Memory B cells function as the foundation of the adaptive immune system, creating a physiological catalogue of foreign antigens that can be used to “recognize” invading pathogens and trigger an immune response. Memory B cells can survive for decades, creating long-term protection against diseases that have been encountered previously.
Immune monitoring is used to track the numbers of pathogen-specific memory B cells present in order to estimate disease progression, as well as the magnitude and functionality of the immune response generated against a specific pathogen. In order to do this, memory B cells need to be activated by a complex cascade of specific signaling cues generated by helper T cells. The authors hoped instead to create an immune monitoring assay that significantly simplifies this process, using small proteins known as cytokines to mimic helper T cell activation.
To carry out their study, the authors used peripheral blood mononuclear cells (PBMC) from 24 healthy donors recruited by HemaCare. Donors were selected on the basis of whether they had a history of immune vaccine exposure to various flu strains. PBMC were collected by leukapheresis at multiple time-points throughout the year, when it was more or less likely that donors were exposed to the flu virus. PBMC were then seeded into a panel of polyclonal B cell stimulation cultures, using 6 different combinations of known helper T cell cytokines.
The author’s strategy was to test each of these potential memory B cell activation combinations, and determine what, if any, effect they had on the upregulation of antigen-specific memory B cells. They discovered that a combination of the antibody anti-CD40, and cytokine messenger molecules IL-4 and IL-21 resulted in a strong polyclonal B cell upregulation, as measured by FACs analysis. The researchers then used both ELISA and Immunospot assay formats to detect the ratio of antigen-specific memory B cells being activated. They were pleased to find that the new activation protocol selectively activated influenza-specific B cells.
This study shows that helper T cell-dependent memory B cell activation can be replicated using a specific combination of signaling molecules, in a way that substantially mimics physiological activation, and that this activation can be accurately measured in a traditional immune monitoring format.
HemaCare supports this type of research through active management of the industry’s largest searchable donor database. To learn more about our donor recruitment program, please visit us at our website.
Franke F., et al. IL-21 in Conjunction with Anti-CD40 and IL-4 Constitutes a Potent Polyclonal B Cell Stimulator for Monitoring Antigen-Specific Memory B Cells. Cells. 9 (433): 1-16. 2020.