 Immune Cell Abundance Identifier, IMO-Cell AI, is a gene-set signature-based method that accurately estimates the abundance of 24 immune cell types, including 18 T cell subsets, from gene expression data. IMO-Cell AI outperforms other methods in estimating immune cells, particularly on many T cell subsets. The application of IMO-Cell AI to immunotherapy data sets reveals that the abundance of dendritic cells, cytotoxic T, and gamma-delta T cells is significantly higher in responders versus non-responders. Furthermore, an IMO-Cell AI result-based model accurately predicts immunotherapy response with high accuracy, area under Curve 0.80 to 0.91. This article was authored by Yerou Miao, Cheong Cheong, Qian Lei, and others.