Adhesion molecules on intermediate TCR cells. I. Unique expression of adhesion molecules, CD44+ L-selectin-, on intermediate TCR cells in the liver and the modulation of their adhesion by hyaluronic acid.

In addition to thymus-derived T cells, it was demonstrated recently that extrathymically differentiated T cells exist in the liver and other immune organs of mice. Since such extrathymic T cells have T-cell receptors (TCR) of intermediate intensity (i.e. intermediate TCR cells) and constitutively express IL-2 receptor beta-chain (IL-2R beta) similar to natural killer (NK) cells, they are easily distinguished from thymus-derived T cells with a TCR-bright+ IL-2R beta- phenotype (i.e. bright TCR cells). In the present study, the expression of adhesion molecules CD44 and L-selectin was compared between these T-cell subsets. Intermediate TCR cells in the liver and other organs were found to be CD44+ L-selectin- and, inversely, bright TCR cells were CD44- L-selectin+. CD3- IL-2R beta+ NK cells were also estimated to be CD44+ L-selectin-. Hyaluronic acid, which is known to adhere to a CD44 ligand, bound to intermediate TCR cells, but not to bright TCR cells. Among many extracellular matrices, hyaluronic acid induced a prominent decrease in the numbers and proportions of intermediate TCR cells and NK cells in the liver from 6 to 24 hr after in vivo administration. The half-life span of injected hyaluronic acid was approximately 7 hr in the plasma. These results suggest that the CD44 molecule, which is uniquely expressed on intermediate TCR cells and NK cells, is eventually associated with their adhesion to the sinusoidal walls in the liver.