Triggering of effector functions on a CD8(+) T cell clone upon the aggregation of an activatory CD94/kp39 heterodimer

Some T lymphocytes express the CD94 Ag, which is known to form heterodimers with members of the NKG2 family. We have studied the expression pattern an d function of CD94 heterodimers in different alpha beta or gamma delta T ce ll clones, Most of the CD94(+)NKG2A(-) T cells have a low to intermediate e xpression of CD94 Ag, The cross-linking of the CD94/NKG2 heterodimer in one of these CD8 alpha beta CD94(+)NKG2A(-) T cell clones (K14B06) was able to : 1) increase the intracellular concentration of Ca2+, 2) induce the up-reg ulation of CD25 Ag expression and the secretion of IFN-gamma, and 3) trigge r redirected cytotoxicity in a TCR-independent manner. This activatory prop erty was not shared by any other costimulatory molecule expressed by the K1 4B06 T cell clone, including CD8, CD28, CD45, CD69, or CD2 Ags, The immunop recipitation of CD94 heterodimer showed a 39-kDa band with a similar m.w. t o the activatory heterodimer found on some NK clones, A novel form of the N KG2 family (NKG2H) was identified in K14B06. NKG2H protein represents an al ternative spliced form of the NKG2E gene, displaying a charged residue in t he transmembrane portion and a cytoplasmic tail that lacks immunoreceptor t yrosine-based inhibitory motifs, The expression of NKG2H in the cell membra ne through its association to CD94 and DAP-12 molecules supports that it co uld form part of the activatory CD94/Kp39 heterodimer present on K14B06 cel ls.