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Circulating CD2 Monocytes Are Dendritic Cells1 Keith Crawford,*

Summary: Circulating CD2 Monocytes Are Dendritic Cells1
Keith Crawford,*
Dana Gabuzda,
Vassilios Pantazopoulos,* Jianhua Xu,*
Chris Clement,*
Ellis Reinherz,
and Chester A. Alper2
Low levels of CD2 have been described on subsets of monocytes, macrophages, and dendritic cells. CD2 is expressed on about
one-third of circulating monocytes, at levels one-half log lower than on T or NK cells, representing 24% of PBMC. FACS analysis
of CD2 and CD2 monocytes revealed no significant difference in the expression of adhesion molecules (CD11a/b/c), class II Ags
(HLA-DR, -DQ, -DP), myeloid Ags (CD13, CD14, CD33), or costimulatory molecules (CD80, CD86). Freshly isolated CD2 and
CD2 monocytes were morphologically indistinguishable by phase contrast microscopy. However, scanning electron microscopy
revealed large prominent ruffles on CD2 monocytes in contrast to small knob-like projections on CD2 monocytes. After 2 days
of culture, the CD2 monocytes largely lost CD14 expression and developed distinct dendrites, whereas the CD2 monocytes
retained surface CD14 and remained round or oval. Freshly isolated CD2 monocytes were more potent inducers of the allogeneic
MLR and more efficiently induced proliferation of naive T cells in the presence of HIV-1 gp120 than did CD2 monocytes. After
culture in the presence of GM/CSF and IL-4, CD2 monocytes were up to 40-fold more potent than monocyte-derived dendritic
cells or CD2 monocytes at inducing allogeneic T cell proliferation. These findings suggest that circulating CD2 and CD2
monocytes are dendritic cells and the precursors of macrophages, respectively. Thus, dendritic cells are far more abundant in the


Source: Alper, Chester A. - Immune Disease Institute, Harvard University


Collections: Biology and Medicine