Poly(D, L-lactide) (PLA) microparticles containing the ovalbumin (OVA) model antigen were prepared by the double-emulsion and solvent evaporation method, followed by encapsulation with alternating layers of the polyelectrolytes, consisting of protamine sulfate and dextran sulfate of various molecular weights. The physicochemical properties, including particle size and zeta potentials, were characterised. Treatment of mouse macrophages with surface-modified PLA microparticles stimulated the generation of reactive oxygen species (ROS), such as hydrogen peroxide and superoxide, which was detected by the fluorescent probes, 2 ',7 '-dichlorofluorescein diacetate (DCFH-DA) and hydroethidine (HE). Incubation of murine bone marrow-derived dendritic cells (BMDCs) with the encapsulated PLA microparticles enhanced the presentation of OVA soluble antigens in B3Z cells, an OVA-specific CD8(+) T cell hybridoma. Results obtained in this study demonstrated the potential use of polyelectrolyte-encapsulated biodegradable microparticles for delivery of soluble antigens to the antigen presenting cells and stimulation of effective antigen presentation in the context of class I major histocompatibility complex.