Vascular endothelial cell (EC) injury by lipopolysaccharides (LPS) plays a major role in the pathogenesis of gram-negative bacterial sepsis and endotoxic shock. The studies described here were performed to define further the molecular mechanisms involved in the EC responses to LPS. We showed that serum was required for LPS-mediated cytotoxicity for bovine brain microvessel, pulmonary, and aortic ECs and that anti-human CD14 antibodies completely blocked LPS-mediated cytotoxicity for ECs in the presence of human serum. The addition of a recombinant soluble form of human CD14 to serum-free medium restored the LPS-mediated cytotoxicity,

Retinal pigment epithelial (RPE) cells induced to express MHC class II (HLA-DR) by incubation with interferon gamma (IFN-gamma) were investigated for their ability to present a microbial superantigen to T lymphocytes. Superantigens bind to MHC class II antigens and appear to play a role in a number of infectious and autoimmune diseases through stimulation of large numbers of T cells. Primary cultures of human RPE cells treated with IFN-gamma for three days to induce HLA-DR expression bound staphylococcal enterotoxin E (SEE) via HLA-DR and presented SEE to T cells as measured by proliferation of purified peripheral blood T cells and IL-2 synthesis by the Jurkat T cell line. Untreated RPE cells were essentially ineffective as superantigen presenting cells. These results suggest that MHC class II expressing RPE cells could contribute to immune and inflammatory activity in the eye by presenting superantigens to T lymphocytes.

Two antisera were raised in goats against material shed by two different mammary epithelial cell lines into serum-free tissue culture medium . These antisera, when added to the medium of intact, growing mouse mammary tumor cells in the absence of complement, cause distinct and dramatic alterations in cell morphology and adhesiveness . One antiserum (anti-SFM I) causes mouse mammary tumor epithelial cells to round and detach from the substratum . Treatment with the other antiserum (anti-SFM II) does not affect cell-substratum interactions, but causes the cells to convert from an epithelioid to a fibroblastic morphology . Statistical analysis of transmission electron micrographs of control and antibody-treated cells indicates that treatment with anti-SFM II is associated with a substantial reduction in the extent of intercellular junctions, particularly desmosomes . To identify the components with which the two antisera interact, nonionic detergent extracts of mouse mammary tumor cells were fractionated, and the ability of various fractions to block the morphological effects of either antiserum was determined . The whole Nonidet P40 (NP40) extract of the epithelial cells blocked the effects of both antisera . After the extract was subjected to ion exchange and lectin affinity chromatography, two separate fractions were obtained . One fraction blocks anti-SFM I induced rounding and detachment of cells from the substratum . The second fraction blocks the effects of both antisera . The isolation of the former fraction, which has highly restricted number of components, represents a significant first step toward identifying the surface membrane molecule(s) involved in cell-substratum adhesion in epithelial cells.

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