CDNA cloning of lymphotoxin alpha (LT-α) from a marsupial, Macropus Eugenii

Lymphotoxin (LT) is a proinflammatory cytokine with a broad spectrum of immunological activities. While the 'classic' form of the molecule is a secreted homotrimer, now referred to in the literature as LT-α3, it has more recently been recognised that a membrane-bound form of LT exists on activated T lymphocytes and that this represents a complex between LT-α and a closely related type II membrane protein, LT-β. Together with another related cytokine, rumour necrosis factor alpha (TNF-α), these molecules have been extremely well studied in eutherian mammals but not in any other group. Marsupials represent a distinct branch in mammalian evolution to that of eutherians, the two groups having diverged more than 100 million years ago. We report here for the first time, the cDNA cloning of LT-α from a marsupial, Macropus eugenii (tammar wallaby). This sequence was found to be relatively conserved when compared to orthologous sequences from eutherian mammals, sharing an average sequence identity of 70.4% at the nucleotide level and 71.7% at the deduced amino acid level.