Abstract: Methods and compositions are provided for producing monoclonal antibodies capable of distinguishing between antigenic aggregates, which are differentiated by one or a small number of antigenic determinants. The method involves immunization of a mammal to produce spleen cells which are fused with a cell line which is stable in vitro. The hybridized cells are then dispensed into culture wells at a density level which encourages the production of one colony per well. Autologous antigenic aggregates are employed for screening to distinguish the antibodies which discriminate between the antigenic aggregates. Particularly, mice are hyperimmunized with a homogeneous population of T-cells, the immunized mice killed and the spleens removed. The spleen cells are fused with mouse myeloma cells and the resulting hybrids plated at a relatively low density in culture wells. Plates containing fewer than 30% hybrid positive wells are found to have primarily one colony per well.