Isolation, maturational level, and functional capacity of human colon lamina propria plasma cells

Large numbers of plasma cells (PC) localise in the intestinal lamina propria (LP) where they play a critical role in the defence against pathogens. This study analyses the level of maturation reached by normal human colon LPPC in comparison with that of bone marrow (BM) PC.

A technique was designed to purify LPPC by combining collagenase digestion of the mucosal layer and immunomagnetic selection of CD54(+) LP cells. It provided highly purified PC, as demonstrated by morphology, CD38(h) phenotype, and cytoplasmic IgA staining criteria. This procedure allowed comparison of in vitro functional capacities and a broad phenotypic analysis of BMPC and LPPC.

LPPC and BMPC exhibited identical expression of differentiation markers (CD19(-/+), CD20(-), HLA-DR(low/-), VS38c(high)), survival molecules (CD95 (low/-), Bcl-2(+)), and B cell transcription factor profile, as well as similar in vitro Ig secreting kinetics (14 days) and lack of susceptibility to apoptosis by CD95 ligation. In contrast, they markedly differed in adhesion molecule expression, as LPPC showed higher levels of CD44 and CD21 and were alpha 4 beta 7(+) whereas BMPC lacked this integrin and expressed higher levels of CD49d and CD31.

These data indicate that PC at effector sites of the humoral response (BM and LP) show similar high differentiation, survival, and functional features but display a distinctive pattern of adhesion molecules, probably related to their respective homing locations.