Abstract #512

# 512
Calf macrophages exhibit a robust response to LPS which is not affected three weeks after an early life challenge with LPS in vivo.
Filiz T. Korkmaz*1, Aimee L. Benjamin1, David E. Kerr1, 1University of Vermont, Burlington, VT.

Genetic and epigenetic factors may contribute to animal-to-animal variation in innate immune response to infection with epigenetic effects being imposed by differences in early life environment. To evaluate lasting effects of a severe early-life infection on innate immune response capability we exposed 6 pairs of Holstein bull calves, at 8d of age, to either a 0.5 µg/kg intravenous dose of LPS or saline. Three weeks later we established cultures of monocyte-derived-macrophages (MDMs) from 100 mL blood samples by culturing monocytes for 8 d. The cells were then challenged for 24h with 100 ng/mL of LPS. The LPS treated calves demonstrated clinical signs of endotoxin challenge and markedly elevated (P < 0.05) plasma levels of TNF-α (3.2 ± 1.0 ng/mL) and IL-6 (14.4 ± 2.8 ng/mL) at 2h post-challenge. Although there was no significant difference (P > 0.05) between cells from LPS or saline treated calves, the MDMs produced considerable quantities of IL6 and TNF-α in response to LPS, which averaged 2.3 ± 0.4 ng/mL and 190 ± 81 pg/mL, respectively. Likewise, there was a large LPS-mediated induction of IL8 and IL1-β (88.1 ± 37.6 and 1954.9 ± 1166.5 fold change, respectively). Readily detectable expression of TLR4 and CD14 was measured with minor induction due to LPS. No differences (P > 0.05) were measured between groups in LPS-induced gene expression. Relatively large inter-animal variation was found in most parameters with a significant correlation between expression of IL1-β and IL8 (R2 = 0.68, P < 0.01) and TLR4 and CD14 (R2 = 0.57, P < 0.01). Dermal fibroblasts were also isolated from 10 calves to determine how their response to LPS compared with that of the MDMs. Fibroblast TLR4 expression was less than MDM TLR4 expression and this was reflected in lower LPS-induced induction of IL8 and IL-6 gene expression. In conclusion, LPS response in MDMs and fibroblasts is variable between animals, lower in fibroblasts, and is not affected in MDMs 3-wks after a single exposure to LPS at 8d of age. Future studies are needed to determine genetic and epigenetic components which may be influenced by early life environment.

Key Words: innate immunity, epigenetic