T cell effector function and anergy avoidance are quantitatively linked to cell division

We have shown previously that T cells activated by optimal TCR and CD28 ligation exhibit marked proliferative heterogeneity and similar to 40% of these activated cells fail entirely to participate in clonal expansion, To address how prior cell division influences the subsequent function of primary T cells at the single cell level, primary CD4(+) T cells were subjected to polyclonal stimulation, sorted based on the number of cell divisions they had undergone, and restimulated by ligation of TCR/CD28, We find that individual CD4(+) T cells exhibit distinct secondary response patterns that depend upon their prior division history, such that cells that undergo more rounds of division show incrementally greater IL-2 production and proliferation in response to restimulation, CD4(+) T cells that fail to divide after activation exist in a profoundly hyporesponsive state that Is refractory to both TCR/CD28-mediated and IL-2R-mediated proliferative signals. We find that this anergic state is associated with defects in both TCR-coupled activation of the p42/44 mitogen-activated protein kinase (estracellular signal-related kinase 1/2) and IL-2-mediated down-regulation of the cell cycle inhibitor p27(kip1). However, these defects are selective, as TCR-mediated intracellular calcium flux and IL-2R coupled STAT5 activation remain intact in these cells. Therefore, the process of cell division or cell cycle progression plays an integral role in anergy avoidance in primary T cells, and may represent a driving force in the formation of the effector/memory T cell pool.