Phage antibodies against human dendritic cell subpopulations obtained by flow cytometry-based selection on freshly isolated cells.

In one application of phage display technology, large libraries of antibody fragments displayed on phage particles are used to select antibodies that bind to molecules expressed on the surface of eukaryotic cells. The advantage of this method is that antibodies can be selected against antigens in their native configuration, without the need to purify or express the antigen as a recombinant protein. Moreover, this approach may be used to search for novel membrane molecules expressed by subpopulations of cells that are difficult to address by conventional methods, e.g., small numbers of cells present in heterogeneous mixtures. It has been shown that the isolation of cell-bound phages is compatible with immunofluorescence staining and flow cytometric identification and sorting of cells based on multiparameter analysis. Here, we have employed a semi-synthetic phage display library of human single-chain Fv (scFv) antibody fragments in combination with flow cytometry to isolate antibodies against rare populations of precursor and mature dendritic cells (DCs) present in human peripheral blood. DCs are a phenotypically heterogeneous population of professional antigen presenting cells of bone marrow origin with complex and only partly understood developmental relationships and functions. We have isolated phage antibodies against subpopulations of blood DCs and analyzed the distribution of the target antigens. The results show that these phage antibodies are useful tools to further dissect relationships and function of DCs in healthy and diseased tissues.