Comparative accessory cell function of human peripheral blood dendritic cells and monocytes

Area of Science:

• Immunology
• Cell Biology

Background:

• Dendritic cells (DC) and monocytes are crucial peripheral blood mononuclear cells (PBMC) involved in T cell activation.
• Understanding their distinct roles and interaction molecules is vital for immunology research.

Purpose of the Study:

• To compare the T cell activation capacity of human peripheral blood dendritic cells (DC) and monocytes.
• To identify the interaction molecules utilized by these cells during T cell activation.

Main Methods:

• Isolation and characterization of DC (CD33+CD14dim) and monocytes (CD33+CD14bright) from peripheral blood.
• Assessment of accessory cell function using T cell activation assays with immobilized anti-CD3 and allospecific T cell lines.
• Analysis of accessory molecule expression (HLA-DR, LFA-3, ICAM-1, B7) on fresh and cultured cells.

Main Results:

• Freshly isolated DC and monocytes showed comparable accessory function in anti-CD3 and mixed lymphocyte reaction (MLR) assays.
• In vitro preincubation enhanced the accessory function of both DC and monocytes, with cultured cells being comparably active.
• DC were significantly more effective stimulators of freshly isolated allogeneic T cells than monocytes.
• Accessory molecules like ICAM-1, LFA-3, and B7 were used comparably by both cell types, with B7 playing a key role in differentiated APC function.

Conclusions:

• Peripheral blood DC and monocytes require differentiation into mature cells for optimal function, characterized by increased MHC and accessory molecule expression.
• The superior stimulatory capacity of DC for allogeneic T cells, compared to monocytes, is likely due to differences in MHC molecules and/or bound peptides, not accessory molecules alone.