St. Vincent's Institute of Medical Research 1 article published in JoVE Immunology and Infection Quantification of Proliferating Human Antigen-specific CD4+ T Cells using Carboxyfluorescein Succinimidyl Ester Anthony R. Di Carluccio1, Eleonora Tresoldi1, Michelle So1, Stuart I. Mannering1,2 1 Presented here is a protocol for measuring proliferating CD4+ T cells in response to antigenic proteins or peptides using dye dilution. This assay is particularly sensitive to rare antigen-specific T cells and can be modified to facilitate cloning of antigen-specific cells.