Indeed, one dendritic cell can effect more than 1,000 T cells. The review of the research on the antigen-presenting capacity and tolerogenic potential of dendritic cells was provided by Angus Thomson, PhD, DSc, from the Thomas E. Starzl Transplantation Institute at the University of Pittsburgh Medical Center. Although it has been demonstrated that dendritic cells present antigen and initiate T cell activation in vitro , direct in vivo evidence of this process was lacking until Kudo and colleagues observed proliferating T cells in contact with dendritic cells in T-cell areas of rat lymphoid tissue following injection of allogenic dendritic cells. Methods are not yet available to permit in situ detection in normal individuals. T cells specific for a peptide complex after adoptive honing of both cell populations into syngeneic recipients.
Dendritic cells have the capability to both initiate immune response and regulate immune reactivity.
During the life cycle of the cell, dendritic cells progress from an immature to mature form. When cells were matured, they demonstrated the capacity to stimulate both Th1 and Th2 responses. In mice, two major dendritic cell lineage subsets derived respectively from myeloid or lymphoid precursors appear to differ in expression of CD8-alpha, effect on Th subsets, localization in lymphoid organs, and types of immune responses generated in vivo . At the present time, the function of these two dendritic cell subsets remains controversial. It has been suggested that the myeloid-derived subsets prime naive T cells and generate memory responses, while the lymphoid subset induces tolerance.