IN-VITRO RESPONSES OF AVIAN MONOCYTES TO HOMOLOGOUS YOLK

Background: Large volumes of yolk are released into stromal lacunae of the avian ovary during bursting atresia, It is broken down by macroph ages that accumulate in large numbers in the lacunae in the presence o f free yolk. The macrophages may be derived from lacunae-lining cells or from blood monocytes. Methods: Chicken blood monocytes were isolate d from adult laying hens, cultured, and exposed to different concentra tions of homologous yolk, Morphological changes were studies by Light microscopy and transmission and scanning electron microscopy, and the rate of breakdown of yolk micelles was measured by turbidometry. Triti ated thymidine uptake was used to measure monocyte proliferation rate following exposure to yolk. Results: Following exposure to yolk, the c ells rapidly changed from fibroblastlike to macrophagelike cells. The turbidometric results indicated very significant clearing of yolk mice lles by the cultured monocytes. These findings were supported by light and transmission and scanning electron microscopy, which showed these cells to be extremely active in engulfing yolk particles. Conclusions : This process in cultured monocytes is morphologically identical to t hat observed in previous studies in cells lining the lacunae of ovarie s of hens, in which large yolky follicles are undergoing bursting atre sia. Therefore, it should serve as a model for studying yolk resorptio n during this form of atresia. (C) 1996 Wiley-Liss, Inc.