Abstract 5793: Measurement of basophil activation using a flow cytometry method for applications in clinical research and clinical trials

Abstract Background: Basophils are a type of white blood cell that play a role in the immune system, particularly in defending the body against allergens, pathogens, and parasites. Basophils also can contribute to the immune response directed against cancer cells by releasing histamine and other mediators that can enhance inflammation and recruit other immune cells to the tumor site. They express high-affinity immunoglobulin E (IgE) receptors, which are involved in recognizing and responding to antigens presented by cancer cells. Basophils may also play a role in modulating the tumor microenvironment, potentially influencing the effectiveness of immunotherapies and understanding the exact mechanisms make the study of basophil activation an exciting area for developing novel therapeutics. Methods: Basophil cells can become activated when the antigen loaded IgE antibody recognizes and binds to the Fc receptor (FcεRI) on the basophil surface. Basophil activation also causes certain markers to be upregulated on the surface of the cell that can be measured by flow cytometry to determine basophil activity. The basophil activation test (BAT) was conducted with human whole blood samples using a commercially available basophil activation kit. Whole blood specimens from human donors were collected in EDTA blood collection tubes. Blood was stimulated with FCεR1 and fMLP and staining reagent for 25 - 30 minutes at 37°C. Cells were lysed, washed and acquired on the flow cytometer. Results: CCR3 was used to identify the basophil population in human whole blood. CD63 and CD203c were then used to identify the unstimulated and stimulated state of the cells. Upon stimulation there was an increase in CD63 and CD203c expression on the surface of the basophils. Conclusions: These results showed that the basophil activation can be measured using flow cytometry with the increased expression of CD63 and CD203c on stimulated basophils. This method could be used to help scientists in clinical research and clinical trials to monitor allergic diseases, predict responses to immunotherapy, and assess the effectiveness of treatments, including immunoncology drugs. Citation Format: Jennifer J. Stewart, Lynette Brown. Measurement of basophil activation using a flow cytometry method for applications in clinical research and clinical trials [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 5793.