Expression of the macrophage scavenger receptor in atheroma. Relationship to immune activation and the T-cell cytokine interferon-gamma.

Scavenger receptors mediate internalization of modified lipoproteins and foam cell transformation of monocyte-derived cytokines. We investigated macrophage scavenger receptor (MSR) expression in monocyte-macrophages from human peripheral blood and in atherosclerotic lesions and analyzed its relationship to T lymphocytes and immunoregulatory cytokines by immunohistochemistry and polymerase chain reaction (PCR). Antibodies specific for the two MSR isoforms were generated by immunizing rabbits with isoform-specific synthetic peptides conjugated to keyhole limpet hemocyanin. In human atherosclerotic plaques, these antibodies stained macrophages and foam cells in a pattern that corresponded to the distribution of the macrophage marker CD68. CD3-positive T cells and alpha-actin-positive smooth muscle cells exhibited no reactivity to the anti-MSR antibodies. The frequency of cells stained with antibodies to MSR type I was equal to that of cells stained for type II, suggesting that most macrophages coexpress both isoforms. Reverse transcription (RT)-PCR analysis confirmed that both MSR isoforms were expressed in all plaques examined. There was, however, a tendency toward a lower immunohistochemical staining intensity for MSR type I and a decreased number of lipid-rich foam cells in T cell-rich areas. The mRNAs for interleukin-2 and interferon-gamma, two major products of activated T cells, were detected by RT-PCR in all plaques tested. This indicates that activation of T lymphocytes occurs in atherosclerotic plaques. Since interferon-gamma downregulates MSR expression, these observations suggest a potential mechanism for local regulation of MSR expression in the atherosclerotic plaque.

Gas chromatographic determination of polychlorinated biphenyls and some chlorinated pesticides in sewage sludge using a glass capillary column.

Gas chromatographic methods for the determination of polychlorinated biphenyls and DDT (with some of its metabolites) in sewage sludge samples and similar materials are described. The sample is extracted with a mixture of hexane, acetone and water. After separation, the hexane phase is reduced in volume and divided into two aliquots, one of which is first shaken with 7% fuming sulphuric acid to remove lipids, and then with potassium cyanide to eliminate interference by elemental sulphur. The other aliquot is evaporated to dryness and heated with ethanolic potassium hydroxide. The two aliquots are injected into a gas chromatograph fitted with a glass capillary column and an electron capture detector. Hexabromobenzene is used as an internal standard. Polychlorinated biphenyls are determined quantitatively by comparing the peaks of the sample with those of Clophen A 50 or A 60. The individual percentage composition of the chlorobiphenyls in the polychlorinated biphenyl oils is used. The capillary column is coated with silicone oil SF 96 according to a described procedure.