Immunological Balancing Act

Science Signaling  17 Mar 2009:
Vol. 2, Issue 62, pp. ec101
DOI: 10.1126/scisignal.262ec101

Secretory immunoglobulin A (IgA) plays a crucial role in the gut by promoting immune tolerance to food and the microflora that colonize the gut. IgA is produced by B cells with the help of CD4+ T follicular helper cells. How these helper CD4+ T cells are generated in the gut is unclear. Tsuji et al. found that suppressor Foxp3+CD4+ T cells can differentiate selectively into follicular B cell helper T cells (TFH) in Peyer’s patches, specialized lymphoid tissue in the gut, but not in other lymphoid tissue. Differentiation of suppressor T cells into TFH cells requires down-regulation of the suppressor T cell–specific transcription factor Foxp3 and interaction with B cells. Thus, flexibility of T cell populations and the specific environment of the gut help to maintain the critical balance between immune tolerance and activation.

M. Tsuji, N. Komatsu, S. Kawamoto, K. Suzuki, O. Kanagawa, T. Honjo, S. Hori, S. Fagarasan, Preferential generation of follicular B helper T cells from Foxp3+ T cells in gut Peyer’s patches. Science 323, 1488–1492 (2009). [Abstract] [Full Text]