The present invention is based, in part, on our discovery of immunoglobulins (e.g., immunoglobulin G (IgG)) polypeptides (e.g., murine or human IgG, such as human IgG1) that are aglycosylated yet retain the ability to bind to an Fc receptor, such as an activating Fc receptor (e.g., Fcy RIIA and/or FcyRIIIA).