A novel functional cell surface dimer (kp43) serves as accessory molecule for the activation of a subset of human gamma delta T cells.

Abstract

Kp43 is a cell surface molecule expressed by NK cells, gamma delta T lymphocytes, and a small subset of CD56+ alpha beta T cells. In the present study the distribution and function of Kp43 on gamma delta T cells is described. The expression of Kp43 on freshly isolated gamma delta T-cell populations derived from fetal and adult tissues was biased toward memory V gamma 2+/V delta 2+ T lymphocytes and appeared to be up-regulated after activation. Several gamma delta T-cell clones were derived from different sources. Adult V gamma 2+/V delta 2+ T-cell clones expressed the highest levels of Kp43, V delta 1 T-cell clones derived from periphery expressed moderate levels, whereas some thymus V delta 1 T cells and fetal gamma delta T-cell clones displayed low or undetectable levels of Kp43 molecule. Based on the effect of a specific mAb, this dimer appears to be fully functional as previously shown for NK cells. The stimulation of Kp43+ gamma delta T-cell clones with a combination of anti-CD3 and anti-Kp43 co-immobilized on a solid substratum enhanced both the expression of cell surface CD25 and the secretion of TNF-alpha. The restricted expression and functional activity of the Kp43 dimer suggests that it may play an important regulatory role in activation, selection, Ag recognition, and responsiveness of a subset of gamma delta T cells.