Principles of health and safety in agriculture. Dosman JA, Cockcroft DW, eds., Boca Raton, FL: CRC Press, Inc., 1989 Oct; :113-115
The results of studies of cellular immune reactions induced by grain dust and grain dust extracts were summarized. Rats were exposed to 1.0 milligram spring-wheat dust in 0.25 milliliter of saline, intratracheally. Peripheral blood cell and bronchoalveolar lavage (BAL) fluid lung cell counts were obtained 24 hours after exposure. Peripheral blood and lavage fluid neutrophil counts were significantly increased by dust exposure. Spleen cells from normal rats were cultured and incubated with 0 to 50 micrograms per milliliter (microg/ml) aqueous oat, barley, durham-wheat, spring- wheat, and corn dust extracts. The effects on their proliferative activity were assessed after treatment with concanavalin-A (conA) and phytohemagglutinin (PHA) and by measuring uptake of tritiated thymidine. All dust extracts induced a dose dependent proliferative response, barley dust being the most potent and corn dust the least active. The responses were most pronounced after treatment with conA and PHA. Alveolar macrophages recovered by BAL from normal healthy rats were incubated with 50microg/ml aqueous oat, barley, durham-wheat, spring-wheat, and corn dust extracts for 24 hours. Production of interleukin-1 (IL1) by the macrophages was determined. The endotoxin content of the extracts was measured. All dust extracts induced production of IL1. The extent of IL1 production was not significantly correlated with their endotoxin content. Rats were administered aqueous extracts of oat or spring-wheat dust intratracheally. Twenty four hours later, BAL was performed and the lavage fluid was assayed for IL1. No IL1 activity was detected. Alveolar macrophages recovered from the lavage fluid were incubated overnight in media alone and then assayed for IL1. Macrophages recovered from grain dust exposed, but not control, rats demonstrated IL1 activity. The authors conclude that aqueous extracts of grain dust contain substances that stimulate the immune system in a nonspecific manner. These findings suggest that grain dusts can stimulate inflammatory reactions by a variety of mechanisms.