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Characterisation of CD4 T cells in healthy and diseased koalas (Phascolarctos cinereus) using cell-type-specific monoclonal antibodies

Manger, C, Armitage, CW, Timms, P, Corcoran, LM & Beagley, KW 2016, Developmental and Comparative Immunology, vol. 60, no. 1, pp. 80-90.

An initial cell-type-specific monoclonal antibody (mAb) for koalas has been developed. The anti-CD4 mAb is able to detect CD4+ T lymphocytes at various bodily sites using a range of analytical techniques. The mAb can also be used to detect vaccine-induced Chlamydia-specific CD4+ T cells in the peripheral blood mononuclear fragments of immunised koalas.

  Monoclonal antibodies (mAbs) are engineered antibodies designed to mimic the body’s natural immune response to an antigen. Here, an anti-koala CD4 mAb was created based on the koala CD4 gene. Three analytical techniques were then employed to use the mAb to examine the characteristics of CD4 cells. Using flow cytometry, the levels of CD4+ T helper cells were found to be 41.1% of the total lymphocyte population in the spleen, 36.3% in the lymph nodes, and 23.8% in the peripheral blood of the koala. Using western blot analysis, the size of the koala CD4 molecule was found to be 52 kDa. Using immunohistochemistry, CD4+ cells were found in the paracortical region and germinal centres of the spleen and lymph nodes. In vitro, the mAb showed that CD4 cells proliferated in response to UV-inactivated Chlamydia pecorum and recombinant chlamydial antigens in koalas previously vaccinated with an anti-chlamydial vaccine, but not in unvaccinated koalas.

  CD4+ T lymphocytes are known to play an important role in the body’s immune response to chlamydial infection from studies of other animals. For many species, mAbs have been developed to further our understanding of that animal’s immune response to chlamydial infection. Prior to this study, no such immune reagent had been developed for the koala. Without the koala mAb, it was difficult to assess the species’ specific immune response after infection or vaccination with an anti-chlamydial vaccine. The authors of this study targeted the CD4+ T cell lineage for mAb development in order to facilitate a greater understanding of the koala’s natural and vaccine-induced immune response to chlamydial infections, which pose a significant threat to wild populations.

  The development of a koala-specific CD4 mAb contributes greatly to understandings of the koala’s immune response to not only chlamydial infections but also microbial infections, koala retrovirus and autoimmunity. In other species, similar immunological techniques have strengthened conservation efforts, such as the development of a diagnostic marker for Tasmanian devil facial tumour disease. Similarly, the development of immunological techniques for the koala is likely to create new opportunities for the conservation of this threatened species.


Summarised by Joanna Horsfall


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