Indecisive interleukin-4?

T cells that express a constitutively activated form of the integrin LFA-1 (bottom) have restricted mobility compared to those expressing wild-type LFA-1 (top). show that immune cells expressing a perpetually activated form of the integrin LFA-1 get traction at the front of the cell, but get stuck from behind. Their lagging ends prevent them from crawling through the endothelium and initiating a normal immune response. Integrins, such as LFA-1, are adhesive molecules that switch between active and inactive conformations and control migration of circulating immune cells to sites of infection and inflammation. LFA-1 is also required for the formation of stable interactions between T cells and antigen presenting cells (APCs). Previous studies had shown that both tumor-specific T cell responses and neutrophil migration are compromised in the absence of this integrin. The importance of LFA-1 deactivation, however, has been less clear. In vitro studies have shown that locking LFA-1 in its activated conformation impairs both neutrophil chemotaxis and T cell activation. Semmrich et al. now confirm these findings in vivo, and show that lymphocytes from Indecisive interleukin-4?