Regulation of adhesion molecule expression by t cell activation in vivo

In vitro stimulation of naive T cells results in discrete changes in adhesion molecule expression that are thought to play a role in the differential trafficking of naive and memory T cells in vivo. Three-color flow cytometry was used to assess the temporal pattern of adhesion molecule expression during antigenmediated T cell activation in vivo. A small population of transgenic T cells specific for ovalbumin peptide 323-339/l-A^d were transferred into syngeneic BALB/c mice, and activated by immunization with ovalbumin. The percentage of transgenic T cells in the draining lymph node increased during the first 5 days, then decreased rapidly through day 10, and then stabilized at pre-immunization levels. Adhesion molecule expression was analyzed from day 0 through day 21 of immunization. There was a stable decrease in L-selectin and CD45RB levels, consistent with conversion of naive T cells to memory T cells. The expression of other adhesion molecules could be subdivided into three distinct phenotypes: 1) expression that increased during the first three days and remained stable thereafter (CD11a, CD11b, CD18, u6 and 11 integrin subunits); 2) expression that initially remained unchanged but exhibited a slight increase in expression after 10-14 days (CD11c, a1 and <x2 integrin subunits); and 3) bimodal expression with a transient increase between days 3 and 10 in the ratio of low:high expressing cells (u4, aE, and <7 integrin subunits). Other adhesion molecules, such as CD2 and CD48, showed no change in expression during the three weeks following immunization. These studies provide in vivo confirmation of the differential expression of integrins (and other adhesion molecules) on naive and memory T cells. Furthermore, these results illustrate unique patterns of changes in adhesion molecule Dhenotvpe durina the naive to memory conversion in vivo.