Survival in rectal cancer is predicted by T cell infiltration of tumour-associated lymphoid nodules

SummaryLymphoid nodules are a normal component of the mucosa of the rectum, but little is known about their function and whether they contribute to the host immune response in malignancy. In rectal cancer specimens from patients with local (n = 18), regional (n = 12) and distant (n = 10) disease, we quantified T cell (CD3, CD25) and dendritic cell (CD1a, CD83) levels at the tumour margin as well as within tumour-associated lymphoid nodules. In normal tissue CD3+, but not CD25+, T cells are concentrated at high levels within lymphoid nodules, with significantly fewer cells found in surrounding normal mucosa (P = 0·001). Mature (CD83), but not immature (CD1a), dendritic cells in normal tissue are also found clustered almost exclusively within lymphoid nodules (P =