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Soluble alpha 1 acid-glycoprotein is considered an "acute phase protein" with an inhibitory effect on lymphocyte activity; it has recently been shown that a lymphocyte modulatory variant of alpha 1 acid-glycoprotein has a positive role on T cell activation. It is not clear whether the presence of this glycoprotein on lymphocyte membranes is due to an endogenous production or to a passive uptake of soluble alpha 1 acid-glycoprotein by its carbohydrate moiety. Our data show an increase of membrane alpha 1 acid-glycoprotein both in peripheral blood lymphocyte and T-enriched lymphocytes after phytohemagglutinin stimulation. Peripheral blood lymphocyte enzymatic treatment by neuraminidase does not affect alpha 1 acid-glycoprotein expression while pronase digestion induces a strong decrease of alpha 1 acid-glycoprotein positive lymphocytes and a resynthesis after phytohemagglutinin stimulation. Furthermore, the presence of alpha 1 acid-glycoprotein was prevalently, found on helper/inducer lymphocytes. These data support the hypothesis of a synthesis of alpha 1 acid-glycoprotein by T lymphocytes during their activation process.

Polyadenylated RNA was isolated from acute-phase liver and transcribed into cDNA. After homopolymer tailing this was cloned into the PstI site of pBR322 which was used to transform E. coli RR1 cells. Clones containing cDNA corresponding to acute-phase proteins were identified by differential hybridization with 32P-labelled normal and acute-phase cDNA. A clone synthesizing about 10 ng of alpha 1-acid glycoprotein per E. coli colony was detected using a solid-phase based immunochemical procedure. The identification of the clone was verified by competition assay with authentic alpha 1-acid glycoprotein isolated from serum and by restriction analysis of the cDNA inserted into pBR322.

Albumin, fibrinogen, alpha 1-acid glycoprotein and cysteine proteinase inhibitor were determined by electroimmunoassay in the media of primary cultures of rat hepatocytes exposed to dialysed supernatants of rat, mouse and human macrophages or to recombinant human and murine interleukin 1 and tumour necrosis factor. Recombinant cytokines in the range of 1 to 1000 ng/ml caused only reduction of albumin synthesis and slight stimulation of alpha 1 acid glycoprotein production while crude preparations of macrophage cytokines elicited typical acute phase response. The results suggest that interleukin 1 or tumour necrosis factor are not likely the principal mediators responsible for the direct stimulation of normal rat hepatocytes to acute phase protein synthesis.