Investigation of alpha nascent polypeptide‐associated complex functions in a human CD8 + T cell ex vivo expansion model using antisense oligonucleotides

Summary In order to determine molecules involved in the differentiation and proliferation of human CD8 + cells, two ex vivo expansion models were established: coculture of freshly purified human CD8 + cells with irradiated autologous feeders (AF) or stimulation with anti‐CD3. Two different proliferation kinetics of CD8 + cells and expression patterns of CD57 were observed between these conditions. Differential display reverse transcriptase–polymerase chain reaction was applied to investigate the differential expression of mRNA species between CD8 +  CD57 + and CD8 +  CD57 – populations. A differentially expressed RNA species called alpha nascent polypeptide associated complex (α NAC) was found at a higher level in CD8 +  CD57 – cells than in CD8 +  CD57 + cells. In the presence of AF, the expression of α NAC was reduced on culturing whilst proliferation increased. Similarly, in cultures stimulated with anti‐CD3, α NAC reverted to its inactive form and differentiation and proliferation increased. Using a phosphorothioate‐modified oligodeoxynucleotide antisense directed specifically against α NAC mRNA, protein expression was inhibited and increased CD8 + cell proliferation and CD25 expression were observed irrespective of the culture conditions. This suggests that α NAC protein is antiproliferative molecule. This is the first description of the function of the α NAC protein in human CD8 + T cells.