The MRC OX-34 antigen of rat T lymphocytes was purified and peptide sequences were obtained. Oligonucleotide probes were synthesized and cDNA clones coding for the antigen were isolated and sequenced to yield a predicted protein sequence for the molecule that fitted the peptide data. Comparison of this sequence with that for human CD2 determined by Sewell et al. showed that OX-34 is rat CD2. The primary structure of the molecule was notable for a moderately large cytoplasmic domain of unusual sequence and also for its highly significant relationship to CD4 antigen in the membrane proximal extracellular region and the transmembrane sequence. A relationship to the Ig superfamily can be argued for the two extra cellular domains of CD2, even though neither fits the standard pattern for Ig-related domains. Within the T lymphocyte lineage, rat CD2 seemed to be present on all stages with the exception of approximately 50% of the thymic CD4-,CD8- cells. In addition, the antigen was prominent on most macrophages in the spleen but not found on peritoneal or liver macrophages. CD4 antigen is also expressed on T lymphocytes and macrophages, and thus CD2 and CD4 appear similar in their cellular expression as well as structural characteristics.
Similarities in sequences and cellular expression between rat CD2 and CD4 antigens.
A F Williams, A N Barclay, S J Clark, D J Paterson, A C Willis; Similarities in sequences and cellular expression between rat CD2 and CD4 antigens.. J Exp Med 1 February 1987; 165 (2): 368–380. doi: https://doi.org/10.1084/jem.165.2.368
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