Provided herein are oligomeric reagents, including oligomeric reagents of streptavidin or a streptavidin mutein, compositions thereof, and methods for manufacturing oligomeric reagents, including methods for reliably manufacturing oligomeric particle reagents of a desired size. In some cases, the reagents are oligomeric particle reagents containing a plurality of binding sites for agents, and thus the one or more agents are multimerized by reversibly binding to the oligomeric particle reagent, e.g., thereby creating a multimerized oligomeric particle reagent, having stimulatory agents multimerized thereon. Also provided are methods for using the oligomeric reagents for incubation or culturing, such as to induce stimulation of expansion, activation, and/or survival, of a composition of cells such as a population of lymphocytes. In some aspects, the disclosure provides methods and reagents for the stimulation, survival, persistence, activation, or other effect of cell populations that involve binding of agents to a molecule on the cell surface.