ABSTRACT
OBJECTIVE: To identify eosinophil progenitor cells in feline bone marrow, establishing an assay method to use in studies of eosinophilopoiesis and eosinophilopoietic factors in cats. ANIMALS: Healthy, laboratory animal source cats. PROCEDURE: Sources of colony-stimulating activity were prepared by conditioning media with bone marrow, spleen, and blood mononuclear cells from cats infected with Toxocara canis. Bone marrow cells were aspirated and cultured to develop the eosinophil progenitor cell assay and to test cells from 9 healthy cats in the assay. RESULTS: Optimal conditions for identifying colony-forming units-eosinophil and cluster-forming units-eosinophil were as follows. Bone marrow mononuclear cells (10(5)) were plated in 1 ml of supplemented medium, fetal bovine serum, and agar. The source of eosinophil growth factor(s) was bone marrow-conditioned medium made in the presence of 2.5 micrograms of concanavalin A/ml; other conditioned media also supported eosinophil colony growth. Dishes were incubated for 7 days at 37 C and 7% CO2. The colony-forming units-eosinophil formed aggregates of > 50 Luxol fast blue-positive cells and had dispersed morphology; the cluster-forming units-eosinophil formed aggregates of < 50 cells. CONCLUSION AND CLINICAL RELEVANCE: Similar to other species, cats have separate and distinct eosinophil progenitor cells. The eosinophil progenitor assay may be used to characterize altered kinetics of eosinophilopoiesis, to assess eosinophil growth factors, and to evaluate therapeutic regimens that might be useful in the management of excess eosinophil production.
