Comparative ultrastructure and expression of L-selectin on bovine αβ and γδ T cells

Abstract

Compared to most ␣␤ T cells, bovine ␥␦ T cells express two to five times the level of L-selectin and have a much higher capacity to roll on monolayers of endothelial cells, platelets, and leukocytes in assays done under physiological flow. To gain additional insight into the basis for these differences, scanning (SEM) and transmission (TEM) electron microscopy were used to compare the cellular ultrastructure of bovine ␥␦ and ␣␤ T cells and to study the expression of L-selectin on these cells. It is interesting that ␥␦ T cells had more than twice as many microvilli and other surface projections on a per cell basis as ␣␤ T cells. This was not due to the ␥␦ T cell being larger; after adhesion and fixation procedures used for the EM studies, ␥␦ T cells averaged 3.9 ؎ 0.01 m in diameter, whereas ␣␤ T cells were slightly larger (5.7 ؎ 0.01 m in diameter). As previously shown for human neutrophils and lymphocytes, L-selectin was preferentially localized to the tips of the microvilli. In contrast, WC1, a lineage-specific antigen on ␥␦ T cells, was localized on the plasmalemma between the microvilli. Our findings suggest that more effective rolling of ␥␦ T cells in various in vitro flow assays may be due to the greater number of microvilli on ␥␦ T cells leading to a higher number of contact sites during adhesion events. In addition, this physical parameter may explain the increased level of Lselectin expression on ␥␦ versus ␣␤ T cells because L-selectin is clustered at the tips of microvilli. J. Leukoc. Biol. 64: 104-107; 1998.

Cell Adhesion Molecules, Leukocyte Trafficking, and Strategies to Reduce Leukocyte Infiltration

“…9,25 Expression of L-selectin by bovine ␥␦ T cells is much higher than that of bovine ␣␤ T and B cells. [26][27][28][29] The significance of this high concentration of expression remains to be determined, but calves have a relatively high number of ␥␦ T cells, and selectin adherence may be very critical to the activity of these cells and immune surveillance.…”