The purity of CD4+ T lymphocytes (mean ± standard deviation) after isolation from peripheral blood mononuclear cells (PBMC) was 91.9 ± 2.8% and 92.8 ± 2.8% in LE and HE cows, respectively, and dot plots from representative LE and HE cows are presented in Fig. 1A to H. The oxygen consumption rate (OCR) in non-stimulated CD4+ T lymphocytes was affected by the interaction (P < 0.0001) between feed efficiency and time (Fig. 2A). This evidence concerns the gene CD4 and hereditary elliptocytosis.