Method of identifying fetal antigens or cell surface markers using phage display technology

A method of isolating binding members recognizing an antigen of a target cell of limited availability in a heterogeneous mixture of target cells and non-target cells comprising the steps:

• a. identifying the target cells,
• b. contacting said target cells with a binding member generating system that allows linkage between the genotype and the phenotype of the binding member and is selected from the group consisting of:
• ribosome display, DNA display, yeast display, bacterial display, retroviral display and phage display,
• c. washing said target cells to avoid drying,
• d. protecting binding members associated with said target cells with a shield, wherein the size of said shield is 60-200 μm in width and placed close to the target cells,
• e. minimizing the number of binding members isolated recognizing non-target cells by subjecting the non-target cells to UV light capable of introducing cross-links in the genetic material of the binding members, whereby the genetic information is rendered non-replicable, said shield from step d protecting binding members recognizing a target cell against said UV light, and
• f. isolating binding member(s) recognizing the antigen of the target cell.