Biomarkers for the detection and identification of a precursor of conventional dendritic cell (cDC) (pre-DC) and its cell subsets (pre-cDC1 or pre-cDC2), are defined, which include CD169, CD327, AXL, CD271, CD324 and combinations thereof for detecting pre-DCs. Methods for detecting a disease or condition, prognosis of an existing disease or condition comprising determining the number of pre-DC cells in sample from a subject as compared to control, as well as methods of treating a patient comprising administration of antibodies against CD169, CD327, AXL, CD271, CD324 and combinations thereof are also disclosed. In addition, an immunogenic composition comprising one or more binding molecules specific for one or more biomarkers or antigen of a target disease and/or one or more cells selected from the group consisting of early pre-DC, pre-cDC1 and pre-cDC2 are also disclosed for eliciting an immune response against an infectious disease or cancer.