Unsupervised clustering of CD4⁺ T cells from PID and normal healthy donors by nonnegative matrix factorization (NMF). (A) Heat map of log₂-transformed expression data, with genes organized into naive and memory metagenes. Expression levels are indicated by the color scale, with red and blue respectively representing high and low relative expression. (B) Visualization of expression levels of naive and memory metagenes by memory CD4⁺ T cells and naive CD4⁺ T cells from normal healthy donors and PID patients. Naive CD4⁺ T cells clustered tightly together and could not be distinguished from each other irrespective of genotype.