Abstract: The disclosure is directed to a biodegradable particle comprising a polyester or polyester blend, a first protein that binds to an immune cell, and a second protein that promotes proliferation and/or activation of immune cells, and a third soluble protein or small molecule encapsulated within the particle. The second protein is a fusion protein comprising at least a portion of an antibody and at least a portion of a cytokine (i.e., an immunocytokine). The disclosure also is directed to methods for treating a disease or condition in a subject (e.g., an autoimmune disease) comprising administering the aforementioned biodegradable particle to the subject.