title: Innate and acquired immune responses in crossbred cattle
Creators: name: Young, Fiona Jane
Publisher: name: University of Glasgow
Year: 2002
Subjects: subject: Animal sciences, Immunology

description: Resistance to infection by pathogenic organisms is critical for survival of livestock under commercial farming conditions. Understanding the complex processes involved in immunity to infection is essential to allow future selection of animals for disease resistance to become an attainable goal in livestock production. The overall aim of this study was to assess various aspects of immune function in a genetically defined population of male and female Holstein Friesian cross Charolais cattle from six months of age. One aspect of the study assessed the in vitro proliferation of peripheral blood mononuclear cells (PBMC) induced by Staphylococcus aureus or Phytohaemagglutinin (PHA) in over 300 second generation animals consisting of F2, Holstein-Friesian backcross and Charolais backcross individuals. Variation in S. aureus-induced, PHA-induced and control PBMC proliferation was found among individuals at each of the time points assessed. Statistical analyses by Residual Maximum Likelihood (REML) identified a significant effect of sex on all of the parameters assessed and a significant effect of control PBMC proliferation on S. aureus-induced and PHA-induced PBMC proliferation. Overall, males had higher levels of both specific and non-specific immunity measured by S. aureus-induced, PHA-induced and control in vitro PBMC proliferation. Following REML analysis, the control in vitro PBMC proliferation was found to have a regression coefficient greater than zero and less than one, which indicated that in this study, calculation of immunity using stimulation indices (SI) or delta counts per minute (Delta c.p.m.) would have been inaccurate and would have resulted in misleading interpretation of the data. On several occasions, sample age and year of birth were also identified as significant factors. The sample age and year of birth were found to have different effects on specific and non-specific immunity. Specific immune function, measured by S. aureus-induced PBMC proliferation, was shown to increase with sample age of the individual, whereas, non-specific immune function, measured by PHA-induced PBMC proliferation, was shown to decrease with sample age. Specific immune function, measured by S. aureus-induced PBMC proliferation, was shown to decrease in the animals born in the 1998 to 2000 cohorts, whereas, non-specific immune function, measured by PHA-induced PBMC proliferation was shown to increase in the animals born in the 1998 to 2000 cohorts. Following REML analyses, the cross and sire of the animal were found to be significant at several of the time points. Variation in immune function was identified among crosses with the Holstein-Friesian backcross animals having greater levels of S. aureus-induced PBMC proliferation than the Charolais backcross animals. In contrast, the Charolais backcross animals were identified as having greater levels of PHA induced PBMC proliferation than the Holstein-Friesian backcross animals. In addition, a small subset of animals for which additional MHC RFLP patterns were available, were ranked for S. aureus-induced and PHA-induced in vitro PBMC proliferation. This study identified that animals with high specific immune responses, measured by S. aureus- induced PBMC proliferation, may have low non-specific immune responses, measured by PHA-induced PBMC proliferation, and also, conversely, that animals with high non-specific immune responses may have low specific immune responses. (Abstract shortened by ProQuest.).