Investigation of human spleen dendritic cell phenotype and distribution reveals evidence of in vivo activation in a subset of organ donors

Although the mouse spleen dendritic cell (DC) is perhaps the most intensive ly studied DC type, little has been published concerning its human equivale nt. In this report, rare event flow cytometry and in situ immunofluorescenc e were used to study the surface phenotype and distribution of HLA-DR+ CD3( -)14(-)16(-)19(-) human spleen DC. Spleens from organ donors with different clinical histories were used. Most (81% +/- 9%; n = 14) spleen DCs express ed high levels of the integrin CD11c, CD11c(+) DCs were distributed in 3 di stinct regions-the peri-arteriolar T-cell zones, the B-cell zones, and the marginal zone, where they formed a ring of cells surrounding the white pulp , just inside a ring of CD14(+) red pulp macrophages, apparently more regul arly organized than the previously described marginating DC population in t he mouse spleen. The T-cell zones contained CD86(+) DCs, among which a subp opulation expressed CD83. These mature/activated CD86(+) DCs represented a minority (12% +/- 8%) of total spleen DCs in most organ donors: most spleen DCs are immature, In 3 of 18(17%) donors, however, most (54%-81%) of splee n DCs were CD86(+), suggesting that in vivo DC activation had occurred, In one donor, a radical shift in DC distribution from the marginal zone to the T-cell zones was also observed, This activation of spleen DCs in vivo was reminiscent of the effects of experimental microbial product injection in m ice, and it seemed to correlate with bacterial infection or multiple trauma . (Blod. 2001;97:3470-3477) (C) 2001 by The American Society of Hematology.