1. Department of Immunobiology, Yale University School of Medicine, New Haven, Connecticut 06520, USA
2. Pulmonary Division, Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA

Correspondence to: Akiko Iwasaki¹ Correspondence and requests for materials should be addressed to A.I. (Email: akiko.iwasaki@yale.edu).

Abstract

CD4⁺ T helper cells are well known for their role in providing critical signals during priming of cytotoxic CD8⁺ T lymphocyte (CTL) responses in vivo. T-cell help is required for the generation of primary CTL responses as well as in promoting protective CD8⁺ memory T-cell development¹. However, the role of CD4 help in the control of CTL responses at the effector stage is unknown. Here we show that fully helped effector CTLs are themselves not self-sufficient for entry into the infected tissue, but rely on the CD4⁺ T cells to provide the necessary cue. CD4⁺ T helper cells control the migration of CTL indirectly through the secretion of IFN- and induction of local chemokine secretion in the infected tissue. Our results reveal a previously unappreciated role of CD4 help in mobilizing effector CTL to the peripheral sites of infection where they help to eliminate infected cells.

1. Department of Immunobiology, Yale University School of Medicine, New Haven, Connecticut 06520, USA
2. Pulmonary Division, Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA

Correspondence to: Akiko Iwasaki¹ Correspondence and requests for materials should be addressed to A.I. (Email: akiko.iwasaki@yale.edu).