Safety and quality of food contact materials. Part 1: evaluation of analytical strategies to introduce migration testing into good manufacturing practice.

The results of a research project (EU AIR Research Programme CT94-1025) aimed to introduce control of migration into good manufacturing practice and into enforcement work are reported. Representative polymer classes were defined on the basis of chemical structure, technological function, migration behaviour and market share. These classes were characterized by analytical methods. Analytical techniques were investigated for identification of potential migrants. High-temperature gas chromatography was shown to be a powerful method and 1H-magnetic resonance provided a convenient fingerprint of plastic materials. Volatile compounds were characterized by headspace techniques, where it was shown to be essential to differentiate volatile compounds desorbed from those generated during the thermal desorption itself. For metal trace analysis, microwave mineralization followed by atomic absorption was employed. These different techniques were introduced into a systematic testing scheme that is envisaged as being suitable both for industrial control and for enforcement laboratories. Guidelines will be proposed in the second part of this paper.

The primary immune response in mice. 3. Retention of sheep red blood cell immunogens by the spleen and liver.

The antibody-inducing activities of foreign red blood cell immunogens sequestered in the spleens and livers of mice injected with sheep erythrocytes were evaluated during the early periods of the immune response. Estimates of immunogenicity, obtained from the magnitudes of anti-sheep red blood cell hemolysin responses evoked in sensitized recipient mice by subcellular tissue fractions prepared from these phagocytic organs, showed that the liver and spleen differ greatly in their handling of this particulate antigen. The liver, functioning primarily as a scavenger organ, destroys completely the immunogenicity of the heterologous erythrocytes in 12 hr. In contrast, the spleen handles foreign erythrocyte immunogens in at least two different ways: approximately 90% of the initially sequestered activity is rapidly destroyed by the spleen in 6 hr, but the remaining activity, associated chiefly with a tissue fraction possessing the sedimentation properties of "light mitochondria," is retained at a significant level for 3 days, and then progressively decreases to a low level until the 7th day. A correlation of the observed changes in the properties of the immunogenic tissue fraction with known cellular events in the spleen stimulated by antigens indicates that the retention of the degradable erythrocyte immunogen is essential for stimulating and maintaining immune reactions in this antibody-producing organ.

The primary immune response in mice. I. The enhancement and suppression of hemolysin production by a bacterial endotoxin.

The manner in which a single injection of S. typhosa endotoxin effects the primary hemolysin response to sheep erythrocytes in the mouse has been shown to depend on the dosage, route, and time of administration of the endotoxin, as well as on the route employed for the injection of antigen. The normal production of antibody, following an intravenous or an intraperitoneal injection of red blood cells, is suppressed if the bacterial lipopolysaccharide is given before and by the same route as the antigen. The response to an intraperitoneal injection of sheep red cells is also inhibited if preceded by an intravenous injection of endotoxin. By contrast, hemolysin formation to intravenous antigen is enhanced considerably by a previous intraperitoneal injection of endotoxin, and the response both to intravenous and to intraperitoneal injections of the antigen increases if the endotoxin is given by the same route either simultaneously or shortly after the foreign red cells. These findings are discussed in regard to the physiological action of bacterial endotoxins and the early events in antibody formation.

The primary immune response in mice. II. Cellular responses of lymphoid tissue accompanying the enhancement or complete suppression of antibody formation by a bacterial endotoxin.

The effects of a single injection of a bacterial endotoxin on the cellular changes of a primary immune response to a standard dose of sheep red blood cells were studied in the spleens and mesenteric lymph nodes of mice. Daily histological comparisons of these organs in mice, injected with endotoxin, or with antigen, or both, showed that endotoxin given simultaneously with sheep red blood cells, as antigen, significantly enhanced all of the cellular changes that appear in the mesenteric lymph nodes and spleens of mice that form antibody when that antigen is given alone. First, in the white pulp of the spleens and cortical regions of the nodes, there appeared an early and excessive proliferation of the large pyroninophilic cells which seems to be responsible for the earliest formation of antibody, as judged by this work and that of others cited in the body of the paper. Polymorphonuclear cells invaded the spleens of these animals early after simultaneous challenge with antigen and endotoxin, and in far greater numbers than have ever been seen in mice given the same antigen without endotoxin. "Activated" germinal centers formed in the lymphoid tissue either 1 day before the appearance of antibody in the blood stream or on the same day, and they became larger than in the mice given antigen only. On the other hand, these specific and characteristic cellular changes failed to appear in mice prevented from forming any antibody at all by injections of endotoxin given 2 days before the antigenic challenge. These findings are discussed in the light provided by data from recent reports of others as well as in the light of the accompanying paper (1) which demonstrated not only the enhancement of antibody formation following simultaneous injections of antigen and endotoxin, as already known, but a totally unexpected, complete suppression of its formation when endotoxin was given 2 days before antigen.