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

We have shown previously that T cells activated by optimal TCR and CD28 lig ation exhibit marked proliferative heterogeneity and similar to 40% of thes e activated cells fail entirely to participate in clonal expansion, To addr ess how prior cell division influences the subsequent function of primary T cells at the single cell level, primary CD4(+) T cells were subjected to p olyclonal stimulation, sorted based on the number of cell divisions they ha d undergone, and restimulated by ligation of TCR/CD28, We find that individ ual CD4(+) T cells exhibit distinct secondary response patterns that depend upon their prior division history, such that cells that undergo more round s of division show incrementally greater IL-2 production and proliferation in response to restimulation, CD4(+) T cells that fail to divide after acti vation exist in a profoundly hyporesponsive state that Is refractory to bot h TCR/CD28-mediated and IL-2R-mediated proliferative signals. We find that this anergic state is associated with defects in both TCR-coupled activatio n of the p42/44 mitogen-activated protein kinase (estracellular signal-rela ted kinase 1/2) and IL-2-mediated down-regulation of the cell cycle inhibit or p27(kip1). However, these defects are selective, as TCR-mediated intrace llular calcium flux and IL-2R coupled STAT5 activation remain intact in the se cells. Therefore, the process of cell division or cell cycle progression plays an integral role in anergy avoidance in primary T cells, and may rep resent a driving force in the formation of the effector/memory T cell pool.