CD28 and ataxia telangiectasia: A heterogenous expression of CD31, CD95 and CXCR3 on a minor fraction of the cells was observed (Figures S3 and S4). The CD45RAdimCCR7+CD27+CD28+ phenotype combined with the absence of exhaustion or activation markers suggests that these cells are phenotypically positioned between the naive and CM population (Figures 2C, D). While the presence of a dominant population may be of relevance for further characterization of AT patients, we decided to exclude these abnormal populations from further analysis of the CD4 and CD8 T cell populations.