T cell activation: in vivo veritas

Barbara Fazekas De St. Groth, Adrian L Smith, Caroline A Higgins
2004 Immunology and Cell Biology  
Phenotypic changes in CD4 + T cells undergoing antigen-dependent activation were compared in vivo and in vitro . The most obvious difference was in expression of CD25, the alpha chain of the high affinity receptor for IL-2. High level expression of CD25 in vivo is restricted to a small fraction of the cells at the leading edge of the cell division profile, whereas all activated cells express high levels of CD25 in cultures responding to antigen. Because IL-2 is known to upregulate expression of
more » ... CD25 in preactivated T cells, this suggests a difference in IL-2 exposure in the two responses. A number of other markers, including CD54, show a similar difference in the pattern of expression in vivo and in vitro . Using 6-colour flow cytometry, it was demonstrated that the small percentage of cells expressing CD25 in vivo coexpresses a very high level of a number of other activation markers, including CD38, CD44 and Ly-6A/E, suggesting that these may also be upregulated by autocrine IL-2.
doi:10.1111/j.0818-9641.2004.01243.x pmid:15186257 fatcat:bm3hi7cb6zfgzicw4l7sxnkf44