Our Perspectives section this month contains two articles exploring the role of follicular dendritic cells (FDCs) in immunity. FDCs are specialized stromal cells with extensive dendrites that can present immune complexes at the cell surface through interaction with Fc receptors or complement receptors. The role of these complexes on FDCs is a controversial issue. Ann Haberman and Mark Shlomchik argue that immune complexes sequestered by FDCs have a role in supporting B-cell proliferation and differentiation in a non-specific manner and are not strictly required for the development of germinal centres and memory B-cell maintenance. However, Marie Kosco-Vilbois argues that a role for FDCs in the development of B-cell responses should not be completely ruled out, although it is possible to detect certain B-cell responses in the absence of an FDC network or a classical germinal-centre reaction, or when immune complexes are absent.

Dendritic cells (DCs) also feature in a review article this month. DC-SIGN is a C-type lectin that interacts with various pathogens through binding of carbohydrates. It has recently been shown that HIV-1 uses DC-SIGN as a Trojan horse to enter DCs, such that infectious virus is then efficiently transmitted to T cells. Yvette van Kooyk and Teunis Geijtenbeek explain how HIV-1 and other pathogens subvert DC function and escape immune responses by manipulating DC-SIGN interactions and signalling.

Other reviews in this issue cover the function of defensins in host defence, the regulatory mechanisms controlling the production of IgE antibodies, the signalling pathways of members of the tumour-necrosis factor superfamily, and the cellular and molecular mechanisms used by helminths to enable them to achieve long-term infections and prevent an effective host response.