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Age-dependent immune response in Merino sheep
D L Watson1, I G Colditz, M Andrew
1CSIRO Division of Animal Health, Armidale, NSW, Australia.
Research in Veterinary Science
|September 1, 1994
Summary
Young sheep exhibit a distinct immune profile compared to mature sheep, with differences in lymphocyte populations and reduced interferon-gamma production. Adjuvants like Quil A show potential in enhancing immune responses in younger animals.
Area of Science:
- Immunology
- Veterinary Science
- Comparative Immunology
Background:
- The immune system undergoes significant changes from youth to maturity.
- Understanding age-related immune differences in sheep is crucial for animal health and disease management.
Purpose of the Study:
- To compare the numerical and functional immune attributes of lymphocytes in young versus mature sheep.
- To investigate age-related differences in immune cell populations, cytokine production, and antibody responses.
Main Methods:
- Analysis of lymphocyte populations (CD4+, B cells, T19+) in blood, lymph, and skin.
- In vitro culture of blood lymphocytes to assess interferon-gamma production.
- Evaluation of serum antibody responses to Brucella abortus lipopolysaccharide (LPS) with and without adjuvants (Quil A, dextran sulphate).
- Assessment of skin contact hypersensitivity and T cell phenotypes in response to specific antigens.
Main Results:
- Young sheep had lower CD4+ cell proportions but comparable or higher B cell and T19+ cell prevalence.
- Lymphocytes from young sheep produced less interferon-gamma.
- Adult sheep showed greater antibody responses to LPS; Quil A improved young sheep responses, while dextran sulphate did not.
- Skin hypersensitivity was lower in young sheep, but T cell phenotypes in antigen-elicited infiltrates were comparable.
Conclusions:
- Young sheep possess a distinct immunological profile characterized by reduced CD4+ cells and impaired interferon-gamma production, indicating a relative immune deficiency.
- Adjuvant therapy, particularly with Quil A, holds promise for overcoming hyporesponsiveness and potentially improving disease resistance in young sheep.