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M Hebdon

Publications and source records attributed to M Hebdon.

3 recordsLinked to original sources

Phorbol ester-induced lymphocyte adherence: selective action on NK cells.

Treatment of human peripheral blood lymphocytes (PBL) with phorbol dibutyrate (PDBU) for 20 to 45 min at 37 degrees C induces adherence of 5 to 30% of the cells to plastic. The adherent cells (pAd) were highly enriched in NK cells on the basis of the following findings: 1) they exhibit high NK and ADCC activity but do not lyse the NK-resistant cell line, Daudi; 2) cytotoxic activity is enhanced by pretreatment with interferon-alpha (IFN-alpha); 3) the surface markers of these cells, as determined with monoclonal antibodies, are consistent with NK cells; and 4) they are enriched with cells morphologically similar to large granular lymphocytes. Conversely, the PDBU-nonadherent cells were substantially depleted of NK cells. The fact that the pAd cells do not lyse the Daudi line and that their NK activity can be further augmented by IFN-alpha would suggest that the pAd are enriched for NK cells rather than changed in their characteristics as a result of the separation procedure. Moreover, no consistent and appreciable modulation of NK activity induced by PDBU was observed. This report therefore demonstrates that PDBU selectively induces NK adherence of NK cells, which may have practical as well as biological implications.

Antibody-Dependent Cell Cytotoxicity↗

Properties of the interaction of fluoride- and guanylyl-5'-imidodiphosphate-regulatory proteins with adenylate cyclase.

The mechanism of activation of adenylate cyclase by guanylyl-5'-imidodiphosphate [Gpp(NH)p] and NaF has been investigated by studying the reconstitution of Gpp(NH)p and NaF sensitivity of an enzyme rendered insensitive to these agents by differential detergent extraction of a particulate brain enzyme. Such reconstitution can be achieved by the addition of macromolecular regulatory factors from membranes of various tissues. Trypsin digestion and thermal inactivation provide evidence for the existence of two distinct regulatory functions, one capable of restoring the Gpp(NH)p response and another the NaF response. The regulatory protein(s) seem to interact with their respective activators in an easily reversible, divalent cation-independent reaction. This appears to be followed by a high-affinity interaction between the catalytic and regulatory components of adenylate cyclase in a slow, temperature-dependent, divalent cation-dependent process tha produces the persistently activated state of the enzyme. The enzyme activation can be reversed by methods that separate catalytic from regulatory components and the resulting enzyme activity can be restimulated by the reconstitution technique.

Adenylyl Cyclases↗