For example, the frequencies of naïve (CD45RA+ CCR7+ CD27+ CD28+) CD4+ and CD8+ T cell subsets were positively associated with the ISIOGTT (insulin sensitivity index (ISI) obtained from the oral glucose tolerance test (OGTT)) and inversely correlated with the HOMA-IR (homeostasis model assessment of insulin resistance) in older participants, whereas the percentage of central memory (CD45RA− CD27+ CD28+) CD4+ T cells was negatively associated with the ISIOGTT and positively associated with the HOMA-IR. Here, CD28 is linked to Insulin resistance.