Meeting Abstract

125.4  Monday, Jan. 7  The cost of an immune response to Escherichia coli in Gallus gallas ISERI , V.J. ; KLASING, K. C.*; Univ. California, Davis kcklasing@ucdavis.edu

There are a variety of costs associated with an immune response to potential pathogens. These costs were quantified in a model using the domestic chicken challenged with an i.v. dose of dead E. coli that was sufficient to cause a vigorous innate immune response and protective levels of immunoglobulins, but did not trigger immumopathology. In young growing chicks, a systemic E. coli challenge results in a 29% decrease in growth. About 2/3 of this decrease is due to decreased food consumption and about 1/3 is due to the immune response and accompanying metabolic inefficiencies that include impaired digestion and increased metabolic rate. Quantification of the amount of lysine, which was used as a sentinel for nutrient flux, in the cells and proteins of the systemic immune system indicates that they contain only 0.39% of the chicken’s entire lysine content; however this amounts doubles during the acute phase response to E. coli (first day). The adaptive response (cellular and antibody) occurs much later, is much smaller and is fueled by the decline in the innate response. To put this in perspective, the additional lysine needed to support the acute phase response is equivalent to 5% of the lysine in the two major pectoralis muscles. Thus, the costs of a protective immune response are very high but they are not dominated by direct consumption of nutrients by the systemic immune system.