MESSENGER-RNAS ENCODING CCKB BUT NOT CCKA RECEPTORS ARE EXPRESSED IN HUMAN T-LYMPHOCYTES AND JURKAT LYMPHOBLASTOID-CELLS

We previously reported the existence of pharmacologically related gast rin/CCKB type receptors (CCKB-R) in a variant of Jurkat T lymphoblasto id cells (JK(CD3(-)CD4(+))). We studied here the expression of mRNAs e ncoding CCKA and CCKB receptors in various human white cells by means of Reverse Transcription-Polymerase Chain Reaction (RT-PCR). Using CCK B-R specific primers, we detected a significant expression of CCKB-R m RNA in JK(CD3(-)CD4(+)) cells. These transcripts were also expressed, at a lower level, in two other Jurkat crones (JK(CD3(+)CD4(-)) and JK( CD3(+)CD4(+))), in peripheral blood lymphocytes (PBL) and in purified CD4(+) and CD8(+) lymphocytes. Activation of Jurkat cells and PBL by T cells mitogenic lectins (jacalin, phytohemaglutinin) did not modify C CKB-R mRNA expression. In all these cells, using CCKA-R specific prime rs, we could not amplify any specific cDNA fragment corresponding to t his receptor. Neither CCKB-R nor CCKA-R mRNAs could be detected in mon ocytic cells. Our data show for the first time a constitutive expressi on of CCKB-R transcripts in lymphoid cells. Moreover, the modulation o f immunocyte functions by cholecystokinin-related peptides could occur through CCKB-R rather than CCKA-R and affect lymphocytes rather than monocytes.