CD4 and ventilator-associated pneumonia: Encouragingly, following the unbiased kinome measurements of ~350 kinases in peripheral blood mononuclear cells (PBMC) depleted of CD4+ T cells, several PKC (protein kinase C) isoforms, especially PKC-α and PKC-β, which play a critical role in regulating T and B-cell activation and survival64, were upregulated at 8 h vs. baseline in VAP (Fig. 4h, Supplementary Fig. 5).