Correlation of transferrin receptor (CD71) with Ki67 expression on stimulated human and mouse T cells: The kinetics of expression of T cell activation markers.

T cell activation is a fascinating, yet tightly regulated cascade of events that lead to the induction of cytokine and expression of activation molecules that eventually result in divergent immune responses. Analyzing the qualitative and quantitative nature of T cell activation in different immunological conditions provides valuable information about the immune responses mediated by different agents or vaccinations. We evaluated the kinetics of CD4(+) and CD8(+) T cell activation markers such as CD25, CD38, CD69, CD71 and Ki67 following anti-CD3/CD28 stimulation over a time course. Our data show that the kinetics of expression of these activation markers follows a precise and consistent time-course with some differences between mouse and human T cells. Percentage of human T cells expressing CD69 and CD25 reached >90% at 24h stimulation, whereas higher percentage of cells co-expressing CD71 and Ki67 was evident for CD8(+) T cells compared with CD4(+) T cells at 24h. Similar to human T cells, percentage of CD8(+)CD38(+) cells was delayed but reached to >90% on mouse CD8(+) T cells at 48h and on mouse CD4(+) T cells at 72h. After 72h of stimulation all tested activation markers remained at the maximum levels in mouse T cells but interestingly percentages of cells expressing CD69 was significantly reduced in human T cells. Furthermore, these data demonstrate a positive correlation between CD71 and Ki67 expression on both mouse and human T cells from 12h post stimulation. Thus our results define the kinetics of activation markers/proliferation in human and mouse T cells; and may serve a reference for monitoring T cell function in clinical study and vaccinology.