Identification of an alternatively spliced variant of human CD86 mRNA

CD86 is a costimulatory molecule constitutively expressed by human antigen presenting cells which interacts with CD28 and CTLA-4 expressed by T cells. We have recently reported the identification of an alternatively spliced C D86 mRNA variant (CD86 Delta TM) characterized by the deletion of exon 6 wh ich encodes for the transmembrane domain. We report here the identification of an alternatively spliced variant (called CD86 Delta EC) expressed by no nstimulated human monocytes and characterized by the deletion of exons 4 an d 5 which encode for the extracellular V-like and C-like domains, respectiv ely. The activation of monocytes by IFN gamma (i) induces the preferential expression of the transcript encoding for the membrane form and (ii) increa ses the expression of CD86 and of the accessory molecules CD40, CD49d and C D54. These results suggest that resting human monocytes may constitutively express different forms of CD86 which can then influence the activation of T cells. (C) 2001 Academic Press.