Antigen responsive cells in unprimed and antigen-primed chickens

Area of Science:

• Immunology
• Cellular immunology

Background:

• Antigen responsive cells (ARC) are crucial for adaptive immunity.
• Understanding the distribution and function of ARC in avian species provides insights into immune system development and response.

Purpose of the Study:

• To quantify the frequency of ARC specific for mouse red blood cells (MRBC) in immunized and unprimed chickens.
• To investigate the role of ARC and passively acquired plaque-forming cells (PFC) in adoptive antibody formation.
• To assess the immune potential of peripheral blood and spleen cells from unprimed chickens.

Main Methods:

• Cell transfer assay to measure ARC frequency in spleen and blood.
• In vivo immune assay using host embryos to evaluate adoptive antibody formation.
• In vivo immune assay with primary and secondary MRBC injections to assess immune response in unprimed birds.

Main Results:

• ARC specific for MRBC were consistently high in the spleen and blood of MRBC-immunized chickens.
• Adoptive antibody formation in host embryos was primarily due to ARC from immunized donors, not passively acquired PFC.
• Unprimed chickens showed minimal response to a single MRBC exposure but substantial splenic PFC formation after a second injection.
• Peripheral blood and spleen cells from both unprimed and antigen-primed chickens serve as significant reservoirs of immunocyte precursors.

Conclusions:

• The spleen and peripheral blood are significant reservoirs of immunocyte precursors in chickens.
• ARC are readily detectable in immunized chickens, contributing significantly to adoptive immunity.
• A secondary antigen exposure is necessary to elicit a substantial immune response in unprimed chickens, highlighting the importance of immune memory development.