Characterization of antibody V segment diversity in the Tasmanian devil (Sarcophilus harrisii)

The Tasmanian devil (Sarcophilus harrisii) immune system has recently been under scrutiny because of the emergence of a contagious cancer, which has decimated devil numbers. Here we provide a comprehensive description of the Tasmanian devil immunoglobulin variable regions. We show that heavy chain variable (VH) and light chain variable (VL) repertoires are similar to those described in other marsupial taxa: VL diversity is high, but VH diversity is restricted and belongs only to clan III. As in other mammals, one VH and one Vλ germline family and multiple incomplete Vκ germline sequences were identified in the genome. High Vκ variation was observed in transcripts and we predict that it may have arisen by gene conversion and/or somatic mutations, as it does not appear to have originated from germline variation. Phylogenetic analyses revealed that devil VL gene segments are highly complex and ancient, with some lineages predating the separation of marsupials and eutherians. These results indicate that although the evolutionary history of immune genes lead to the expansions and contractions of immune gene families between different mammalian lineages, some of the ancestral immune gene variants are still maintained in extant species. A high degree of similarity was found between devil and other marsupial VH segments, demonstrating that they originated from a common clade of closely related sequences. The VL families had a higher variation than VH both between and within species. We suggest that, similar to other studied marsupial species, the complex VL segment repertoire compensates for the limited VH diversity in Tasmanian devils.

Cracking the egg: an insight into egg hypersensitivity

Hypersensitivity to the chicken egg is a widespread disorder mainly affecting 1-2% of children worldwide. It is the second most common food allergy in children, next to cow's milk allergy. Egg allergy is mainly caused by hypersensitivity to four allergens found in the egg white; ovomucoid, ovalbumin, ovotransferrin and lysozyme. However, some research suggests the involvement of allergens exclusively found in the egg yolk such as chicken serum albumin and YGP42, which may play a crucial role in the overall reaction. In egg allergic individuals, these allergens cause conditions such as itching, atopic dermatitis, bronchial asthma, vomiting, rhinitis, conjunctivitis, laryngeal oedema and chronic urticaria, and anaphylaxis. Currently there is no permanent cure for egg allergy. Upon positive diagnosis for egg allergy, strict dietary avoidance of eggs and products containing traces of eggs is the most effective way of avoiding future hypersensitivity reactions. However, it is difficult to fully avoid eggs since they are found in a range of processed food products. An understanding of the mechanisms of allergic reactions, egg allergens and their prevalence, egg allergy diagnosis and current treatment strategies are important for future studies. This review addresses these topics and discusses both egg white and egg yolk allergy as a whole.