CMRF-44 antibody-mediated depletion of activated human dendridic cells: a potential means for improving allograft survival.

BACKGROUND: Activated dendritic cells (DC) initiate immune responses by presenting antigen, including alloantigen from tissue grafts, to T lymphocytes. The potential to deplete or inactivate differentiated-activated DC during allogeneic transplantation represents a new approach to immunosuppression. METHODS: The authors investigated the potential of the monoclonal antibody CMRF-44, which has specificity for a DC-associated differentiation-activation antigen, to induce complement-mediated lysis of activated human DC. Peripheral blood mononuclear cells (PBMC), or purified DC preparations, were cultured overnight to activate endogenous DC, resulting in the expression of CMRF-44 antigen and CD83. These were then treated with CMRF-44 and complement. Depletion of activated DC was monitored by flow cytometry. RESULTS: Eighty-nine percent of activated (CD83+) DC in cultured PBMC were depleted by treatment with CMRF-44 and autologous serum (AS) (complement source; mean percentage of CD83+-CD14--CD19- cells=0.06%; cf 0.50% for heat-inactivated AS controls, P<0.0005, n=7). Ninety-five percent of cultured purified myeloid DC were depleted by this treatment, compared with only 43% of similarly treated lymphoid DC. Overnight culture also increases CMRF-44 antigen on a proportion of B cells and mononuclears, but only 24% of these cells were depleted. This treatment considerably reduced the ability of PBMC to stimulate allogeneic CD4+ CD45RA+ T lymphocytes. Similarly, the T-cell proliferative responses to recall and naive antigens were significantly reduced. CONCLUSIONS: CMRF-44 may be a suitable candidate for a new selective immunosuppressive strategy, targeting differentiated-activated but not resting DC. It may have applications in preventing GVHD in allogeneic bone marrow transplantation and facilitate immunoacceptance of solid organ allografts.

Granulocyte-colony stimulating factor increases CD123hi blood dendritic cells with altered CD62L and CCR7 expression.

Changes in blood dendritic cell (BDC) counts (CD123(hi)BDC and CD11c(+)BDC) and expression of CD62L, CCR7, and CD49d were analyzed in healthy donors, multiple myeloma (MM), and non-Hodgkin lymphoma (NHL) patients, who received granulocyte-colony stimulating factor (G-CSF) containing peripheral blood stem cell (PBSC) mobilization protocols. Low-dose G-CSF in healthy donors (8-10 microg/kg/d subcutaneously) and high-dose G-CSF in patients (30 microg/kg/d) increased CD123(hi)BDC (2- to 22-fold, mean 3.7 x 10(6)/L-17.7 x 10(6)/L and 1.9 x 10(6)/L-12.0 x 10(6)/L) in healthy donors and MM but decreased CD11c(+)BDC (2- to 10-fold, mean 5.7 x 10(6)/L-1.6 x 10(6)/L) in NHL patients, on the day of apheresis, compared with steady state. After apheresis, CD123(hi)BDC counts remained high, whereas low CD11c(+)BDC counts tended to recover in the following 2-5 days. Down-regulation of CD62L and up-regulation of CCR7 on CD123(hi)BDC were found in most healthy donors and MM patients. CD49d expression was unchanged. Thus, PBSC mobilization may change BDC counts by altering molecules necessary for BDC homing from blood into tissues.