Phenotypes of B and T cells in human intestinal and mesenteric lymph

Background & Aims: Cells in lymph draining the human gut have not been characterized previously. The aim of this study was to phenotype B and T cells present in microlymphatics of Peyer's patches and in mesenteric lymph. Methods: The studies were conducted by multicolor immunohistochemistry, flow cytometry, and immunocytochemistry. Results: In decreasing order of frequency, microlymphatics in Peyer's patches contained naive T (CD3(+)CD45RA(+)alpha(4) beta(7)(low)) and B (slgD(+)CD(20)(+)alpha(4) beta(7)(low)) lymphocytes, memory T (CD45RO+alpha(4) beta(7)(+)) and B (slgD(-)CD(20)(+)alpha(4) beta(7)(+)) lymphocytes, and B-cell blasts (CD19(+)CD38(high)alpha(4) beta(7)(high)). Naive cells were usually positive for L-selectin, memory cells weve either positive or negative, and B-cell blasts were usually negative. Mesenteric lymph contained naive T (similar to 60%) and B (similar to 25%) lymphocytes, memory T and B lymphocytes (similar to 10%), and B-cell blasts (similar to 2%). Cytospins confirmed these results and showed, in addition, that B-cell blasts contained cytoplasmic immunoglobulin (Ig) A, IgM, or IgG in overall proportions of 5:1: <0.5. Conclusions: Our results ave similar to the phenotypes previously described in animal thoracic or mesenteric lymph. A fraction of the B cells stimulated in Peyer's patches are near terminal differentiation (contain cytoplasmic Ig) before they enter peripheral blood. Many memory cells, and most if not all B-cell blasts entering lymph show an adhesion molecule profile (alpha(4) beta(7)(high) L-selectin(low)) in keeping with the presumed phenotype of lymphoid cells destined for mucosal effector sites such as the gut lamina propria.