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The expression of the insulin-like growth factor binding protein-2 (IGFBP-2) was assayed in mononuclear cells originating from different organs of the immune system. All mononuclear cells studied did express IGFBP-2, but the expression level was found to be dependent on the cell type and origin of the cell. T cells showed a higher expression of IGFBP-2 mRNA than did B cells, and CD34+ stem cells expressed IGFBP-2 mRNA at a high level. Expression was highest in bone marrow and thymus. Stimulation of peripheral mononuclear cells resulted in a marked increase of IGFBP-2 mRNA and also intracellular IGFBP-2, as analysed by fluorescence staining. This increase parallels the increase of other known T-cell activation markers. Furthermore, the increase of intracellular IGFBP-2 seems to precede T-cell blast formation and all T cells in active phases of the cell cycle have high levels of IGFBP-2. Our results provide a basis for further investigations on the contribution of the IGF-system to the regulation of T-cell proliferation and differentiation. IGFBP-2, in particular, may have an important influence in the regulation of T-cell activation and proliferation. A 23187, calcium ionophore IGF I/II, insulin-like growth factor-I/II IGFBPs, insulin-like growth factor binding proteins PBMC, peripheral blood mononuclear cell MNC, mononuclear cell MACS, magnetic-activated cell sorting GAPDH, glycerinaldehydphosphate RT-PCR, reverse transcriptase–polymerase chain reaction. [ABSTRACT FROM AUTHOR]

Previous work demonstrated that human cytotoxic T cells activated by superantigens can lyse major histocompatibility complex (MHC) class Il-positive target cells as well as MHC class II- negative tumour cells coated with conjugates of monoclonal antibodies and superantigens. In order to decrease MHC class II affinity, and therefore unwanted binding of the superantigen staphylococcal enterotoxin A (SEA) to MHC class H molecules, a point mutation was introduced into the SEA genes This mutation (SEAD227A) resulted in an approximately 3-log reduction of affinity to human leucocyte antigen (HLA)-DR, but cytotoxicity mediated by this mutant superantigen towards antibody-labelled tumour cells is as efficient as cytotoxicity mediated by the native superantigen. We therefore compared the T-cell activating potency of native and mutated SEA. Our data show that SEAD227A is 4- to 5-log less effective than native SEA when activation of resting T cells is assayed in terms of blast formation, expression of cell surface activation markers and cytokine release. Furthermore, presenting either SEA or SEAD227A to MHC Class II-neptive mononuclear cells by MHC class II-negative tumour cells did not result in significant blast formation of T cells, up-regulation of CD25 or cytokine release. This suggests that lysis of MHC class II-negative tumour cells is efficiently induced by monoclonal antibody targeted superantigen, while activation of resting T cells requires additional co-stimulatory signals. [ABSTRACT FROM AUTHOR]