Daniel J. Stechschulte

Mast cell deficiency attenuates progression of atherosclerosis and hepatic steatosis in apolipoprotein E-null mice

Mast cells are important cells of the immune system and are recognized as participants in the pathogenesis of atherosclerosis. In this study, we evaluated the role of mast cells on the progression of atherosclerosis and hepatic steatosis using the apolipoprotein E-deficient (ApoE(-/-)) and ApoE(-/-)/mast cell-deficient (Kit(W-sh/W-sh)) mouse models maintained on a high-fat diet. The en face analyses of aortas showed a marked reduction in plaque coverage in ApoE(-/-)/Kit(W-sh/W-sh) compared with ApoE(-/-) after a 6-mo regimen with no significant change noted after 3 mo. Quantification of intima/media thickness on hematoxylin and eosin-stained histological cross sections of the aortic arch revealed no significant difference between ApoE(-/-) and ApoE(-/-)/Kit(W-sh/W-sh) mice. The high-fat regimen did not induce atherosclerosis in either Kit(W-sh/W-sh) or wild-type mice. Mast cells with indications of degranulation were seen only in the aortic walls and heart of ApoE(-/-) mice. Compared with ApoE(-/-) mice, the serum levels of total cholesterol, low-density lipoprotein and high-density lipoprotein were decreased by 50% in ApoE(-/-)/Kit(W-sh/W-sh) mice, whereas no appreciable differences were noted in serum levels of triglycerides or very low density lipoprotein. ApoE(-/-)/Kit(W-sh/W-sh) mice developed significantly less hepatic steatosis than ApoE(-/-) mice after the 3-mo regimen. The analysis of Th1/Th2/Th17 cytokine profile in the sera revealed significant reduction of interleukin (IL)-6 and IL-10 in ApoE(-/-)/Kit(W-sh/W-sh) mice compared with ApoE(-/-) mice. The assessment of systemic generation of thromboxane A(2) (TXA(2)) and prostaglandin I(2) (PGI(2)) revealed significant decrease in the production of PGI(2) in ApoE(-/-)/Kit(W-sh/W-sh) mice with no change in TXA(2). The decrease in PGI(2) production was found to be associated with reduced levels of cyclooxygenase-2 mRNA in the aortic tissues. A significant reduction in T-lymphocytes and macrophages was noted in the atheromas of the ApoE(-/-)/Kit(W-sh/W-sh) mice. These results demonstrate the direct involvement of mast cells in the progression of atherosclerosis and hepatic steatosis.

Human Mast Cells (HMC-1 5C6) Enhance Interleukin-6 Production by Quiescent and Lipopolysaccharide-Stimulated Human Coronary Artery Endothelial Cells

We examined the effect of intact human mast cells (HMC-1 5C6) and their selected mediators on interleukin-6 (IL-6) production and bone morphogenetic protein-2 (BMP-2) expression in human coronary artery endothelial cells (HCAEC) in the presence and absence of lipopolysaccharide (LPS). Scanning electron microscopy showed that HMC-1 5C6 cells adhere to HCAEC in cocultures. Addition of HMC-1 5C6 cells markedly enhanced the IL-6 production by quiescent and LPS-activated HCAEC even at the maximal concentration of LPS. Furthermore, mast cell-derived histamine and proteases accounted for the direct and synergistic effect of mast cells on IL-6 production that was completely blocked by the combination of histamine receptor-1 antagonist and protease inhibitors. Another novel finding is that histamine was able to induce BMP-2 expression in HCAEC. Collectively, our results suggest that endotoxin and mast cell products synergistically amplify vascular inflammation and that histamine participates in the early events of vascular calcification.

Induction of immunological tolerance in immunoglobulin E B lymphocytes in rats

Immunological tolerance has been induced in 2,4-dinitrophenyl (DNP)-specific bone marrow-derived or B lymphocytes of the IgE AND IgG antibody classes by treatment of rats with the DNP derivative of D-amino acid copolymer, D-glutamic acid, D-lysine (D-GL). The tolerant state is manifested as an inability of treated rats to produce serum anti-DNP antibodies and the failure of peritoneal cells from tolerant animals to release histamine following in vitro antigen challenge. The implications of these and related observations for potential therapeutic measures in clinical hypersensitivity states are discussed.

Isolation of hapten-specific antibodies from reagin-rich rat sera and their use for the preparation of rat peritoneal cells for antigen-mediated histamine release

Abstract Dinitrophenyl-specific antibodies were isolated from reagin-containing rat sera by adsorption to DNP-bovine serum albumin linked to sepharose and elution with DNP-glutamate solutions Hapten was removed by adsorption of DEAE sephadex and the preparation was stabilized with 1% BSA. The procedure takes less than 1 day, and recovery of PCA activity is significantly more than 100 per cent. In addition to IgE, the preparations contained IgCa, IgGb, and γ 1 antibody as determined by radioimmunoelectrophoresis. Reagin-containing antisera with a high PCA titer have a low capacity cells vitro for antigen-specific release of histamine. By contast, using the isolated, hapten-specific antibody fraction, the dilutions needed to prepare cells in vitro for antigen induced release of histamine were comparable to the dilutions which sensitimized rat skin in the PCA reaction. Furthermore, added rat IgGa antibody fraction was a more potent inhibitor of the preparation of cell in vitro when the purified hapten-specific antibody was used than when reagin-rich serum was used. The results lend added support to the belief that the activity of whole reagin-containing sera vitro is compromised at least by the IgGa antibody they contain, regardless of the specificity of these antibodies for any given antigen.

Antigen-antibody mediated desensitization of human lung fragments in vitro

Abstract Human lung fragments incubated with atopic serum and specific antigen exhibited marked inhibition of mediator release upon subsequent antigen challenge. Under the conditions resulting in desensitization, mediators were not released into the sensitizing diffusate, the total tissue histamine stores were not diminished, and added histamine was not significantly metabolized. Incubation of lung fragments, atopio serum, and antigen in a calcium-free 5 mM ethylenediaminetetraacetic acid (EDTA) buffer resulted in blockade of desensitization. Thus the presence of antigen during passive sensitization does not result in mediator release, yet renders target cells unable to respond to subsequent antigen challenge.

Patient-care workshop report

The committee acknowledged the importance of cross-training in both pediatric and adult allergyimmunology. A diseasebut not age-oriented clinic is the preferred method of meeting this requirement. It is recognized that specialized hospitals may be unable to offer a combined pediatric-adult clinic. In this situation, the current recommendation of a 1-day clinic per week for 6 months was considered to constitute a minimal acceptable duration. It is recommended that the cross-training experience be extended and that there be some provision to allow the allergyimmunology fellow to participate in the management of emergencies that may occur in these patients between scheduled clinic visits. In addition to meeting minimal requirements of cross-training by attending a 1-day-a-week clinic for a period of 6 months, it is highly desirable for fellows to gain inpatient management experience in the opposite discipline, that is, medicine for pediatricians and pediatrics for internists. Where this is possible, this experience should be gained by a block experience, that is, total time commitment of the fellow in programs in which a pediatrician and an internist could be exchanged from the opposite components of the program. Where this block system is not possible be-

Immediate Immunologic Reactions: Noncytolytic Mediator Release and Cytolytic Cell Destruction

Two of the principal mechanisms by which immunologic reactions generate chemical mediators of the inflammatory response differ both in their mode of interaction with target cell membranes and in their ultimate effect on these membranes. In the cytolytic reaction [Fig. 1(A)] antibodies of certain immunoglobulin classes (IgM or IgG) bind to the target cell via combining sites specific for antigens which are either intrinsic to the cell membrane or have become passively bound to it. A resultant configurational change in the Fc portion of the antibody (Ashman and Metzger, 1971) is associated with the initiation of a sequence of reactions among certain serum proteins, the components of complement,* contained in the surrounding milieu. The physicochemical characteristics and mechanism of interaction of the nine components have recently been reviewed (Muller-Eberhard, 1968; Ruddy, et al., 1972). Chemical mediators of inflammation are generated during the complement reaction sequence per se, by the limited proteolysis of the components. These mediators represent both major (e.g., C3b, an enhancer of opsonization) and minor (e.g., C3a, an anaphylatoxin) fragments of component cleavage as well as complexes (e.g., C567, a chemotactic principle) formed by the interaction of products from different components. If completion of the reaction sequence occurs on a cell membrane, cytolytic destruction of the cell results which in some instances, may eventuate in mediator release.