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

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 pathces and in mesenteric lymph.

The studies were conducted by multicolor immunohistochemistry, flow cytometry, and immunocytochemistry.

In decreasing order of frequency, microlymphatics in Peyer's patches contained naive T (CD3+CD45RA+ alpha 4 beta 7low) and B (sIgD+CD20+ alpha 4 beta 7low) lymphocytes, memory T (CD45RO+ alpha 4 beta 7+) and B (sIgD-CD20+ alpha 4 beta 7+) lymphocytes, and B-cell blasts (CD19+CD38high alpha 4 beta 7high). Naive cells were usually positive for L-selectin, memory cells were either positive or negative, and B-cell blasts were usually negative. Mesenteric lymph contained naive T (approximately 60%) and B (approximately 25%) lymphocytes, memory T and B lymphocytes (approximately 10%), and B-cell blasts (approximately 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.

Our results are 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 7high L-selectin low) in keeping with the presumed phenotype of lymphoid cells destined for mucosal effector sites such as the gut lamina propria.