This application relates to an in vitro method of producing a polyclonal IgG preparation. The method comprises (i) placing a polyclonal B-cell population enriched in IgG-secreting B cells in a culture medium; and (ii) culturing the polyclonal B-cell population under conditions enabling the production of the polyclonal IgG preparation from the polyclonal B-cell population. This improved method enables the production of antibodies (preferably IgG) and facilitates long-term culture of polyclonal B-cell populations.