Adaptive Antibody Response to a Model Antigen in Captive Altricial Zebra Finches

This post is based off of a paper, written by Killpack TL and Karasov WH.

Background on Zebra Finches:

Avian – Birds, feathered, winged, bipedal, warm-blooded, egg-laying, vertebrate animals http://www.devbio.biology.gatech.edu/?page_id=52

Zebra Finch – Taeniopygia guttata – ground-dwelling Zebra Finch

  • Location: Central Australia
  • Size: Adult Zebra Finch is About 10 cm long (3.9 inches)
  • Food: Grass Seeds and Spray Millet
  • Vocalizations: Chattering Trills and Calls
  • Habitat: Grasslands and Forests, Close to Water, Open Steppes with Scattered Bushes and Trees
  • Life Expectancy: Naturally 5-7 Years, In captivity, 12 years
  • Breeding: Sudden Gathering Behaviors, Building of Nests, 2-7 Eggs / Clutch
  • For Your Amusement: Hand-feeding Zebra Finch Hatchlings: The Altricial behavior of zebra finch  hatchlings can be seen in this video.
  • Zebra Finch Singing – http://www.youtube.com/watch?v=XNCYAZcDuGQ

Definitions:

  • Ontogeny: is the origin and development of an organism. An example of this term is when the fertilized egg develops to mature form. The study of an organism’s lifespan.
  • Altricial: is a pattern of growth and development in organisms that are incapable of moving around on their own soon after hatching or being born.
  • ELISA (Enzyme-linked Immunosorbent Assay): used to detect specific IgY Antibodies. The adaptive immune function was measured using ELISA for KLH-specific IgY antibodies.
  • Fledge: is the stage in a young bird’s life when the feathers and wing muscles are sufficiently developed for flight.
  • Passerines: http://en.wikipedia.org/wiki/Passerine

Summary

Age-related changes in adaptive antibody response in an altricial bird species.

Previous work to this paper, suggests that birds are hypothesized to require at minimum 4 weeks to develop the circulating mature B-cell lineages that express different immunoglobulin specificities.  Zebra finches exhibit altricial species that fledge at adult size less than the average 4 weeks that was hypothesized in previous work. These finches may experience a period of susceptibility during the nestling and post-fledgling periods.

Methods:

To critically test the ontogeny of specific adaptive immune response of altricial zebra finches in this paper, Killpack and Karasov used repeated vaccinations with non-infectious keyhole limpet hemocyanin (KLH) antigen. The nestling zebra finches were inject at 7 days, 14 days, or 21 days post hatching with the KLH-adjuvant emulsions, and then boosted 7 days later. The adult was also vaccinated with the same procedure. Using ELISA (described in definitions above),  The induced KLH-specific IgY andtibodies were measured in the zebra finches.

Results:

As seen in Figure 1, there is not a significant difference among the age groups in corrected KLH antibody levels in response to the priming vaccination. The significant differences

FIGURE 1

seen in this figure are the corrected KLH antibody levels post-boost with the responses in adults (far right of Figure 1). The post-boost antibody responses were significantly lower in the nestling age groups that the adults group. This finding indicates that the mature adults’ secondary antibody response level was not achieved in zebra finches prior to fledging.

Conclusions:

  • Altricial zebra finch nestlings are hatched with limited capacity for endogenous adaptive antibody defense.
  • The capacity for endogenous adaptive antibody defense gradually increases throughout the nestling period.
  • Adaptive antibody response of the nestling age range groups were significantly lower than that of adults. This indicates that the completion of immunological development occurs inpost-fledging zebra finches.

Discussion:

Conclusions from this study set up the path for future studies to focus in and investigate the development of immune resistance and tolerance. The physiology and fitness consequences of antigen exposure and infection that occurs during the nestling period of altricial is the next step in future studies.

The findings in this research are an important contribution to the fields of developmental immunology and ecological immunology. Also, these findings strengthen the utility of zebra finches as a usable model organisms for futures studies when studying immune ontogeny. These finds could also open the door to have important implications for disease ecology. Zebra finches are part of a large order of birds called the Passerines. Passerines play important roles in spreading zoonotic diseases in the wild. They have undeveloped defenses and are vulnerable to virus-carrying insects.

This research shows strengths in presenting findings that contribute to a variety of scientific communities. Developmental immunology, ecological immunology, spreading of diseases, and model organism traits are fields these findings can contribute to.

Killpack and Karasov are the first to present this study, to their knowledge about the age-related changes in adaptive antibody response in an altricial passerine.

References:

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