PubMed · 8844371
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W S Dixon. Additional consultation responses.. https://doi.org/10.1016/s0886-3350(96)80296-3
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Previous reports from our laboratory have demonstrated qualitatively that preabsorbed IgG can enhance long-term macrophage adhesion in vitro. This investigation further characterizes and quantifies the biological effect of adsorbed human IgG on human macrophages and probes the potential mechanisms. Ten-day human monocyte/macrophage cultures on Plastek M (PM), a normally poor cellular substrate for macrophages, confirmed the ability of preabsorbed IgG to dramatically enhance long-term macrophage adhesion. An adsorption solution concentration of 200 microg/mL of IgG was necessary to provide a consistent, optimal cellular response. (125)I adsorption studies indicated Langmuir-style IgG adsorption at low concentrations; however, no adsorption maximum was observed. Additional adsorption analysis revealed that the IgG fragments Fab, F(ab')(2), and Fc adsorb at levels only 20-40% that of the whole molecule. Despite the lower adsorption levels, both preabsorbed Fab and F(ab')(2) were shown to be as effective as whole molecule IgG at enhancing long-term macrophage adhesion. Surprisingly, the preabsorbed Fc fragment demonstrated no IgG-like activity, thereby eliminating the possibility of an Fc receptor-based mechanism. Other possible mechanisms, such as macrophage lectins, novel macrophage Fab receptors, and complement activation by adsorbed IgG and IgG fragments, are discussed.
The effect of specific chemical functionalities on the adhesion of polymorphonuclear leukocytes (PMNs) under flow was investigated using a set of well-characterized, chemically functionalized surfaces prepared by self-assembly of alkanethiolate monolayers on gold surfaces. Terminal functionalities included CH(3), CH(2)OH, COOH, and (OCH(2)CH(2))(3)OH groups. A new surface modification was used to incorporate a phosphorylcholine moiety on the hydroxyl-terminated monolayer. Surface modification was verified using contact-angle measurements, ellipsometry, and X-ray photoelectron spectroscopy. Adhesion on the surfaces was studied in the presence and absence of pre-adsorbed fibrinogen. Fibrinogen adsorption on self-assembled monolayers (SAMs) was quantified using radioisotope detection. PMN adhesion was found to be dependent on the monolayer's terminal functionality. Adhesion was higher on the hydrophobic CH(3) surface and the polar COOH monolayer. Leukocyte adhesion was least on the phosphorylcholine-rich surface, followed by the ethylene-oxide-containing monolayer. Cell adhesion also was low on the hydrophilic OH monolayer. Attachment was decreased with increasing shear rate, exhibiting a three-fold decrease between 20 and 100 s(-1). Fibrinogen adsorption was higher on the CH(3) monolayer but comparable for the other four SAMs. Preincubation of the surfaces with fibrinogen decreased adhesion on all SAMs examined.
Multi-electrode sensor arrays are made of soft and wet materials not easily examined by most microscopic techniques. In this paper, we have demonstrated that low-vacuum scanning electron microscopy (LVSEM) and energy-dispersive X-ray analysis (EDX) are adequate for studying the hydration, swelling, and possible delamination of multi-electrode sensor arrays. We found that the LVSEM environment had no detectable effect on the morphology of Na(+), K(+), and Ca(++) sensors, and EDX analysis indicated that all three membranes have similar compositions. However, once hydrated, the sensors exhibited different behaviors. The K(+) and Ca(++) sensors swelled more than the Na(+) sensor did. This swelling is due principally to water sorption in the membrane. We believe that the larger thickness of the K(+) and Ca(++) membrane is partly responsible for the observed swelling effect. A simple Griffith analysis of the interface rupture confirms the experimental evidence that these thicker membranes also are more prone to delamination failure.