The T cell surface – how well do we know it?
Evans EJ, Hene L, Sparks LM, Dong T, Retiere C, Fennelly JA, Manso-Sancho R, Powell J, Braud VM, Rowland-Jones SL, McMichael AJ, Davis SJ. (2003), Immunity. 19, 213-23
The overall degree of complexity of the T cell surface has been unclear, constraining our understanding of its biology. Using global gene expression analysis, we show that 111 of 374 genes encoding well-characterized leukocyte surface antigens are expressed by a resting cytotoxic T cell. Unexpectedly, of 97 stringently defined, T cell-specific transcripts with unknown functions that we identify, none encode proteins with the modular architecture characteristic of 80% of leukocyte surface antigens. Only two encode proteins with membrane topologies found exclusively in cell surface molecules. Our analysis indicates that the cell type-specific composition of the resting CD8+ T cell surface is now largely defined, providing an insight into the overall compositional complexity of the mammalian cell surface and a framework for formulating systematic models of T cell surface-dependent processes, such as T cell receptor triggering.
Key figure: Cell Surface Molecules Encoded by Transcripts Identified in the Clone 32 SAGE Library
Schematic representations of the defined and proposed CD antigens and TCR components whose expression in clone 32 was detected by SAGE are shown. The two new seven TM proteins identified are also included (italics). The architecture of these proteins is drawn approximately to scale according to the conventions of Barclay et al. (1997). Unconventional domains or those for which there are no structures are labeled “?”. The molecules are colored according to transcript abundance per 100,000: purple, ≤3; blue, 4–9; green, 10–27; orange, 28–81; red, >81. Complexes are represented at the level of the most abundant subunit-encoding transcript.
*Stringently defined, CTL-specific molecules.
‡Five integrin α domains were detected in clone 32 by our analysis: CD11a, CD49a, CD49c, CD51, and CD103, which associate with the integrin β chains CD18, CD29, CD61, and β7. Tags derived from CD18 and CD61 were found at high levels in the library but matched several other genes, preventing abundance determination. Integrin β7 tags were also present, but this protein has not been considered for a CD designation. No tags derived from CD29 were observed, presumably due to sampling effects.