P-Selectin Can Support Both Th1 and Th2 Lymphocyte Rolling in the Intestinal Microvasculature

Abstract

Lymphocyte localization to inflammatory sites is paramount for developing and maintaining an immune response. Rolling is the first step in recruitment, but our knowledge of its mechanisms in Th1 and Th2 CD4(+) lymphocytes is incomplete. Whereas initial studies suggested that Th1 but not Th2 lymphocytes used P-selectin for recruitment, more recent studies have proposed that both subtypes bind selectins. We used intravital microscopy to demonstrate in vivo that polarized Th1 and Th2 lymphocytes both use P-selectin to roll and adhere to cytokine [tumor necrosis factor (TNF)-alpha or interleukin (IL)-4]-activated intestinal microvasculature. The majority of Th1 lymphocyte flux in TNF-alpha- and IL-4-treated animals was P-selectin-dependent. Th1 lymphocytes also interacted with E-selectin to control rolling velocity after TNF-alpha stimulation. Th2 lymphocytes, which make IL-4 but not interferon-gamma, bound P-selectin ex vivo, with more than 95% rolling on P-selectin in vivo. Both Th1 and Th2 lymphocytes regulated rolling velocity by interacting with alpha(4)-integrin. Furthermore, in a model of spontaneous intestinal inflammation (ie, IL-10-deficient mice), both Th1 and Th2 lymphocytes rolled, adhered, and ultimately emigrated into the local microenvironment. These results suggest that both Th1 and Th2 lymphocytes use P-selectin in the initial rolling step in vivo in response to a global activator of the vasculature (TNF), a subtle inducer of P-selectin (IL-4), and pathological inflammation (IL-10-deficient mice).