In vivo expression of interleukin‐8, and regulated on activation, normal, T‐cell expressed, and secreted, by human germinal centre B lymphocytes

Summary T‐cell homing within germinal centres (GCs) is required for humoral B‐cell responses. However, the mechanisms implicated in the recruitment of T cells into the GC are not completely understood. Here we show, by immunohistology, and Northern and Western blots, that in vivo human GC B lymphocytes can express CxC and CC chemokines. Moreover, B‐cell subset‐specific experiments reveal that interleukin (IL)‐8 and regulated on activation, normal, T‐cell expressed, and secreted (RANTES) are predominantly expressed by GC centroblast and centrocytes, suggesting that chemokine expression is essential at stages in which B‐lymphocytes engage in active antigen‐dependent interactions with T lymphocytes. In keeping with this hypothesis, we show that the T cells recruited into the GC correlatively express the receptors for IL‐8 and RANTES. We propose that chemokine expression is a key B‐cell function that facilitates T‐lymphocyte recruitment into the GCs and supports cognate B‐cell : T‐cell encounters. Moreover, our data are consistent with the impaired homing of T cells to secondary lymphoid organs in mice that are either deficient in CC and CxC chemokines or their receptors.