ABSTRACT
Protective and pathological immune responses are dependent on the coordinated and timely interaction of various cell types within distinct microenvironments. In the primary response, dendritic cells (DC) migrate from peripheral tissues, where they take up antigen, to the secondary lymphoid organs, where they present the processed antigen to T cells. The helper cells generated during the primary response interact with antigenspecific B lymphocytes to stimulate antibody production, while effector Th1 or Th2 cells enter peripheral inflamed tissues and interact with other leukocytes, such as eosinophils, mast cells and basophils (in the case of Th2 reactions), or macrophages and neutrophils (in the case of Th1 reactions). Tissue-specific pathways for lymphocyte migration to skin, gut and other tissues have been described.
