High expression of ILT3 and ILT4 is a general feature of tolerogenic dendritic cells

The direct interaction between antigen specific CD8(+) CD28(-) T suppressor cells (T-s) with dendritic cells (DC) results in the tolerization of DC by inducing the upregulation of immunologlobulin like transcript 3 (ILT3) and ILT4. We show here that such tolerogenic DC anergize alloreactive CD4(+) CD45RO(+) CD25(+) T cells converting them into regulatory T cells (T-R), which in turn, continue the cascade of suppression by tolerizing other DC. Interleukin 10 (IL-10) and interferon-alpha (IFN-alpha) also induce ILT3 and ILT4 upregulation in DC, rendering them tolerogenic. This implies a common mechanism of DC-mediated suppression. This finding and the observation that in organ allograft recipients quiescence is associated with the presence in the circulation of donor-specific T, and T, emphasize the importance of the cross talk between tolerogenic DC and T cells in suppression of the immune response. (C) 2003 Elsevier B.V. All rights reserved.