This paper describes the morphology, phagocytic capacity, and response to lipopolysaccharide (LPS) of peritoneal macrophages (MØ) from Japanese quail, following induction by thioglycollate. 1) Analysis by transmission and scanning electron microscopy : Similar to chicken MØ, non-activated (4°C) quail MØ had many gathering processes on the cell surface. Activated (37°C) quail MØ exhibited a few long, extended pseudopodia. The cell nuclei of both non-activated and activated quail MØ differed from chicken cell nuclei in that theycontained one large and several smaller heterochromatic bodies, which were attached to the nuclear membrane and other quail somatic cells. 2) Phagocytic activity for sheep red blood cells (SRBC) : The phagocytic activity for SRBC of MØ from non-immunized quail (niMØ) was significantlyless than that of MØ from SRBC-immunized quail (imMØ) (p&lt
0.05). However, the phagocytic activity of niMØ significantlyenhanced bytreatment of the SRBC with anti-SRBC quail serum (p&lt
0.05). In contrast, the phagocytic activity of imMØ did not change following treatment of the SRBC with anti-serum. These results suggest that the phagocytic activityof quail MØ for SRBC is enhanced byopsonization, but that levels of the opsonin receptor on the cell surface of MØ might be decreased byimmunization with SRBC. 3) Stimulation with LPS : The activityof LPS-stimulated MØ (MTT assay) was greatest 0.5 hours after cultivation began. Following LPS stimulation, quail MØ produced molecules of 44.5 kDa and 73.3 kDa, probably interleukin-6 (IL-6) and carrier protein complexes. © 2004, Japan Poultry Science Association. All rights reserved.