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Immune responsiveness of neonatal chicks and immunocyte precursors from unprimed juvenile chicken donors
1Zoology Department, University of Oklahoma, Norman 73019.
Insights
Chicken immune cells from embryos show delayed antibody production (plaque-forming cell response) compared to neonatal chicks. A second antigen dose is needed for embryonic cells, suggesting a less supportive embryonic environment for immune development.
Area of Science:
- Immunology
- Developmental Biology
- Avian Biology
Background:
- Investigating immune cell precursors is crucial for understanding immune system development.
- Avian models offer unique insights into early immune responses.
- The transition from embryonic to neonatal immunity is a critical developmental window.
Purpose of the Study:
- To compare the immune responsiveness of embryonic and neonatal chicken immunocyte precursors.
- To elucidate the impact of the microenvironment on early immune cell function.
- To determine the optimal conditions for eliciting an antibody-producing cell response in young chickens.
Main Methods:
- Cell transfer model using peripheral blood immunocyte precursors from unprimed chickens (4-6 weeks old).
- Assay of splenic plaque-forming cell (PFC) production in response to mammalian erythrocyte antigens.
- Comparison of immune responses in embryonic hosts versus neonatal chicks (2-9 days old) under single and double antigen exposure protocols.
Main Results:
- Embryonic immunocyte precursors showed minimal PFC production after a single antigen exposure, regardless of dosage.
- A second antigen exposure, 3 days after the first, consistently induced modest to high PFC formation in embryonic hosts.
- Neonatal chicks (8 days old) exhibited consistent PFC production after a single antigen injection, with no enhancement from a double dose protocol.
Conclusions:
- The embryonic microenvironment is permissive but less immunosupportive than the neonatal environment for early immune responses.
- Immune kinetics differ significantly between embryonic and neonatal chickens, with embryonic cells requiring a secondary stimulus for robust antibody production.
- These findings highlight the critical role of the post-hatching environment in supporting the maturation of the immune system in chickens.
Abstract:
The immune responsiveness of immunocyte precursors, obtained from peripheral blood of 4- to 6-wk-old unprimed chickens and assayed with the cell transfer model, was compared with that of neonatal chicks. Little if any splenic plaque-forming cell (PFC) production was observed in the spleens of embryonic cell transfer hosts following a single antigen exposure to weak or moderate dosages of mammalian erythrocytes. However, modest to high PFC formation occurred consistently in the hosts following a second exposure to the same antigen when given 3 days later. Although a single immunization failed to elicit PFC formation in embryo hosts, a single injection of a wide range of antigen dosages into 8-day-old chicks elicited PFC production consistently. When the double immunization protocol was used with 2- to 9-day-old neonatal chicks, the level of immune responses were indistinguishable from those elicited with a single antigen injection. The difference in the immune kinetics observed in embryo hosts may be related to the embryonic microenvironment, which is permissive, but may not be as immunosupportive as that of neonates.