112 Annual AACHT Meeting, 1984

suppresses HLA-DR expression on MO such that they may not function in effective antigen presentation. However, its primary IS mechanism in TX may be that CsA suppresses endothelial HLA-DR on the allograft thus reducing its immunogenicity in vivo.

IDENTIFICATION OF TWO DISTINCT DQ-POSITIVE ACCESSORY CELL POPULATIONS THAT ARE VERY POWERFUL IN INDUCING ALLOGENEIC T CELL RESPONSES IN MAN. Gabriel Nunez, Edward J. Ball, Linda K. Myers, and Peter Stasmy; Department oflnternal Medicine, Uniz,ersi(y of Texas Health Science Center Southwestern Medical School, Dallas, T X

In previous studies we observed that the majority of human monocytes express DP and DR molecules but only a subset (10-40%) has DQ products. In the present experiments, we investigated the capacity of subsets of adherent cells to stimulate allogeneic T cells. DQ+ and D Q - adherent cells were prepared by sorting in the FACS with TU-22, a monoclonal antibody specific for DQ. DQ + accessory cells were 3-20 times more powerful in stimulating primary MLC responses than D Q - cells. Both DQ+ and D Q - adherent cell populations were enriched for monocytes: they had the monocyte-specific markers 63D3 and M3. The weak allostimulating capacity of the D Q - adherent population could not be explained by suppression, as judged from results of mixing experiments, or by poor ILl production, since addition of exogenous ILl did not enhance their stimulating effect. Alloreactive T cell lines specific for DR or DQ were tested to analyze the role of the specific antigens recognized. DQ+ accessory cells stimulated proliferation of DQ restricted alloreactive T cell clones, but DQ - cells failed to stimulate such responses. Interestingly, DQ + cells were also more efficient in inducing DR-restricted T cell responses. To further define the DQ + accessory population, DQ + cells were sorted into M3 + (monocyte marker) and M 3 - by a two-color sorting procedure. Both D Q + M 3 + and D Q + M 3 - populations were highly stimulatory, D Q - M 3 + cells were not. These results suggest there are two DQ+ accessory cell populations: one positive for the monocyte marker M3, probably belonging to the monocyte/macrophage lineage; the other M 3 - , could be similar to dendritic cells recently described in human blood.

FUNCTIONALLY DISTINCT SUBPOPULAT1ONS OF HUMAN BLOOD MONOCYTES DE- FINED BY PEANUT LECTIN (ARACHUS HYPOGEA). T. Mohanakumar and Michael A. Taylor; Virginia Commonwealth University. Richmond. VA

Peanut lectin (PNA), previously thought to be a unique T cell differentiation marker, bound 60% of circulating human monocytes. PNA binding was also observed on peritoneal exudate monocytes but was absent on splenic and other tissue macrophages. Monocytes separated into PNA plus and PNA negative by lectin agglutination and differential sedimentation demonstrated the presence of cytoplasmic peroxidase only in the PNA binding fraction. Upon culture induced maturation of monocytes both PNA binding ability and presence of cytoplasmic peroxidase diminished concomitantly from 82 to 3% and thus seem to correlate with monocyte differentiation. Functional studies of monocyte subpopulations enriched using PNA agglutination demonstrated that PNA plus cells comprise the majority of antibody-dependent cellular cytotoxicity (>90%) activity (ADCC) whereas PNA negative monocytes produced less than 30% of the cytolysis ex- pressed by monocytes. In addition Interleukin-1 (II-1) induced 3H-thymidine