Differential expression of type I insulin-like growth factor receptors in different stages of human T cells

Insulin-like growth factor I (IGF-I) has been implicated to play a regulatory role in T cell development and in T cell function. We investigated the expression of type I IGF receptors on human peripheral T cells related to the maturation and activation stage using the type I IGF receptor-specific monoclonal antibody αIR3. It appeared that 87% of the CD4⁺CD45RA⁺ cells and 66% of the CD8⁺CD45RA⁺ cells were αIR3⁺, whereas only 37% of the CD4⁺CD45RO⁺ cells and 38% of the CD8⁺CD45RO⁺ cells bound αIR3. We also found that the fraction of αIR3⁺ cells within in vivo or in vitro activated (HLA-DR⁺) T cells is markedly lower than in nonactivated (HLA-DR^?) cells. In vitro phytohemagglutinin-activated T cells and CD4⁺CD45RO⁺ cells activated with recall antigens also contained less αIR3⁺ cells (1–6%) than nonactivated cells (30–54%).