Hyaluronan-binding by CD44 reduces the memory potential of activated murine CD8 T cells

Abstract

Expansion and death of effector CD8 T cells are regulated to limit immunopathology and cells that escape contraction go on to generate immunological memory. CD44, a receptor for the extracellular matrix component hyaluronan, is a marker of activated and memory T cells. Here, we show with a murine model that the increase in CD44 expression and hyaluronan binding induced upon CD8 T cell activation was proportional to the strength of TCR engagement, thereby identifying the most strongly activated T cells. When CD44^-/- and CD44^+/+ OT-I CD8 T cells were adoptively transferred into mice challenged with Listeria-OVA, there was a slight increase in the percentage of CD44^+/+ cells at the effector site. However, CD44^+/+ cells were out-competed by CD44^-/- cells after the contraction phase in the lymphoid tissues, and the CD44^-/- cells preferentially formed more memory cells. The hyaluronan-binding CD44^+/+ CD8 effector T cells showed increased pAkt expression, higher glucose uptake, and were more susceptible to cell death during the contraction phase compared to non-binding CD44^+/+ and CD44^-/- OT-I CD8 T cells, suggesting that CD44 and its engagement with hyaluronan skews CD8 T cells toward a terminal effector differentiation state that reduces their ability to form memory cells.

Keywords: CD44; Hyaluronan; Memory CD8 T cell formation; T cell contraction.