Modulation of leukocyte-endothelial cell interactions by infectious agents

The ability of leukocytes, the principal mobile players in host defence, to reach the sites where infectious processes occur is pivotal for interrupting these processes and restoring initial steady-state conditions of the tissues. Numerous factors are responsible for regulating leukocyte trafficking, including the expression of adhesion molecules on both endothelial cells and leukocytes, as well as the unique blend of local cytokines and chemokines induced directly or indirectly within the pathogen-loaded sites. Recently, pathogens have been shown to directly intervene and modify these factors, thus influencing the subsequent immune response. This review will discuss mechanisms whereby pathogens can influence the recruitment of leukocytes to sites of infection.