CX3CR1 and cytomegalovirus infection: To further investigate age-dependent differences between the Vδ1, Vδ2 and Vδ3 γδ T cell subsets in CMV-infected and uninfected individuals, we assessed the expression levels of CD16, NKG2C, CD57, CD8, granzyme A, HLA-DR, CX3CR1, and the frequency of NKG2C+CD57+ cells, as these markers have been associated with CMV infection [17,20,23,33,34,35].