Germinal center B cells constitute a predominant physiological source of IL-4: Implication for Th2 development in vivo

• Protective immunity depends upon the capability of the immune system to properly adapt the response to the nature of an infectious agent. CD4+ Th cells are implicated in this orchestration by secreting a polarized pattern of cytokines. Although Th2 development in animal models and in human cells in vitro to a large extent depends on IL-4, the nature of the cells that provide the initial IL-4 in vivo is still elusive. In this report, we describe the anatomical localization as well as the identity of IL-4-producing cells in human tonsil, a representative secondary lymphoid organ. We demonstrate that IL-4 production is a normal and intrinsic feature of germinal center (GC) B cells. We also show that expression of IL-4 is highly confined to the GCs, in which the B cells constitute the prevalent cellular source. Furthermore, immunofluorescence analysis of colon mucosa reveals a strikingly similar pattern of IL-4-expressing cells compared with tonsils, demonstrating that IL-4 production from GC B cells is not a unique feature of the upper respiratory tract. Our results show that GCs provide the most appropriate microenvironment for IL-4-dependent Th2 polarization in vivo and imply a critical role for GC B cells in this differentiation process.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Immunologi inom det medicinska området (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Immunology in the medical area (hsv//eng)

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