PHENOTYPES OF B-CELL AND T-CELL 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 an d T cells present in microlymphatics of Peyer's patches and in mesente ric lymph. Methods: The studies were conducted by multicolor immunohis tochemistry, flow cytometry, and immunocytochemistry. Results: In decr easing order of frequency, microlymphatics in Peyer's patches containe d 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-c ell 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 c ontained naive T (similar to 60%) and B (similar to 25%) lymphocytes, memory T and B lymphocytes (similar to 10%), and B-cell blasts (simila r to 2%). Cytospins confirmed these results and showed, in addition, t hat 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 patc hes 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.