This invention relates to a novel immunoassay device and method for the determination of antigenic substances. The device essentially comprises a pattern or array of minute antibody-coated spots on the surface of a support. The array of antibody-coated spots is preferably in the form of a rectangular matrix. Each antibody-coated spot is made up of antibodies of a different and distinct specificity. A large number of different antibody-coated spots can be assembled on a very small portion of the surface of the support. The spots serve as tiny, specific immunoadsorbents of cells. The expression of particular surface antigen by cells may be detected by determining to which antibody-coated spot the cells bind.