Dennis J. Beer

The Influence of Histamine on Immune and Inflammatory Responses

Publisher Summary The fact that histamine can influence the immune process at different stages and that it can influence different subpopulations of cells at concentrations that probably exist in vivo during physiologic and pathologic events indicates that it can be seriously considered as a significant modulator of inflammatory and immune processes. Once histamine is made available, it is capable of interacting in the local milieu with lymphocytes/macrophages or other cell types present at the site of the reaction and modulating immune and inflammatory events. Some of its pro-inflammatory effects include stimulating T effector cells to produce chemoattractant and migration-inhibitory lymphokines, thus recruiting other immunocompetent lymphocytes to the reaction site and retaining them there. Some of the anti-inflammatory events mediated by histamine include the activation of suppression cells following their interaction with macrophages and/or their products (IL-1), which leads to the production of HSF. The latter augments the production of prostaglandins by macrophages/monocytes. Histamine may modulate the function of cytotoxic T cells and natural killer cells directly, thereby reducing their ability to mediate damage to their target cells. Histamine inhibition of complement synthesis by macrophages may serve to limit the severity of the inflammatory response.

Serotonin‐stimulated aortic endothelial cells secrete a novel T lymphocyte chemotactic and growth factor

Atherosclerotic lesions contain multiple cell types including smooth muscle cells, macrophages, and T lymphocytes. The development of an extralymphatic T lymphocyte focus of inflammation in this condition requires chemoattractant‐induced cell migration and growth factor‐induced cell activation. In a previous study, we described a novel 13–15‐kDa T lymphocyte‐specific chemotactic cytokine, endothelial cell–derived lymphocyte chemoattractant activity (ED‐LCA), secreted by serotonin‐stimulated bovine aortic endothelial cells that is distinct from previously identified endothelial cell–derived interleukins (IL) 1, 6, and 8. Because of the association between T lymphocyte chemotactic and growth factor activity, in the current study we investigated the effect of ED‐LCA on T cell growth. We assessed its capacity to induce markers of the passage of T cells from the resting (G0) state into the G1 phase of the cell cycle, such as receptors for IL‐2 (IL‐2R) and transferrin (TFR) and class II major histocompatibility complex antigens (HLA‐DR). Incubation of G0 freshly isolated human T lymphocytes for 48 h with chromatographically resolved, partially purified ED‐LCA resulted in a threefold increase in expression of the p55 subunit of IL‐2R, a threefold increase in TFR, and a twofold increase in HLA‐DR. Passage into the G1 phase of the cell cycle was confirmed by cell cycle analysis employing acridine orange. Evaluation of CD4+ and CD8+ T cell subsets by double‐antibody labeling demonstrated that the p55 subunit of IL‐2R was induced in both T cell subsets. Although incubation of human T cells with ED‐LCA alone did not induce proliferation, addition of exogenous IL‐2 to T cells pulsed with ED‐LCA for 24 h caused a proliferative response with a stimulation index of 3. By up‐regulating functional cell surface receptors for IL‐2, ED‐LCA is a competence growth factor for T lymphocytes and primes them to respond to IL‐2. By virtue of its effect on T cells, as a chemotactic and competence factor, this endothelial cell‐derived mitoattractant could participate with other T cell growth factors like IL‐2 in the recruitment and amplification of the extralymphatic T cell component of atherosclerosis. J. Leukoc, Biol. 55: 567–573; 1994.

Restricted secretion of a T-lymphocyte chemotactic cytokine by serotonin-stimulated cultured aortic endothelial cells.

The diversity of biologically active molecules produced by vascular endothelium suggests that the endothelial cell is an active participant in numerous physiological responses, including those of the immune system. In fact, the accumulation of T lymphocytes at extralymphatic inflammatory foci represents a series of interactions between lymphocytes and vascular endothelial cells. These interactions, however, may be modulated by other factors, such as vasoactive amines. In the current study, we report that serotonin-stimulated cultured bovine aortic endothelial cells (BAECs) secrete a T-lymphocyte chemotactic cytokine (endothelial cell-derived lymphocyte chemotactic activity [ED-LCA]). Supernatants from BAECs incubated with 10(-7)-10(-4) M serotonin (5-hydroxytryptamine [5-HT]) enhanced T-cell migration, which peaked at 10(-5) M 5-HT (235 +/- 18% control migration). ED-LCA was not stored in an active form in BAECs; its secretion occurred within 60 minutes of exposure to 5-HT and was blocked by two different 5-HT2 receptor antagonists. ED-LCA was not secreted after exposure of BAECs to histamine or angiotensin II, nor was it secreted by either 5-HT-stimulated bovine pulmonary arterial or human umbilical vein endothelial cells. Physicochemical characterization of ED-LCA demonstrated that it was a trypsin-sensitive protein with an apparent molecular mass of 13-15 kDa. Preparative isoelectric focusing demonstrated pIs of 6.0 and 7.5. When applied to a molecular sieve column, the chemotactic activity corresponding to these pIs eluted in the region of 13-15 kDa. Further investigation demonstrated that partially purified ED-LCA was specific for CD4+ and CD8+ T-lymphocyte subsets and did not enhance the migration of neutrophils or monocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

A human T-T-cell hybridoma-derived lymphocyte chemoattractant factor☆☆☆

Human T-T hybridomas were developed as a strategy for obtaining lymphokines that alter T-lymphocyte motility. Mitogen-stimulated human T lymphocytes were fused with cells of the human CEM lymphoma line and the supernatants derived from these fusion products were assessed for chemoattractant activity in a modified Boyden chamber assay. Supernatants from hybridoma 41B2 enhanced lymphocyte migration to 198 +/- 13% (mean +/- SEM) of control. Characterization by Sephadex G-100 molecular sieve chromatography revealed a single peak of chemoattractant activity corresponding to a molecular weight (MW) of 56,000. This activity eluted from a Sephadex QAE anion-exchange column at 4-6 mS. Subsequent isoelectric focusing in sucrose revealed an isoelectric point of 9.0-9.2. Fractions with activity after sequential molecular sieve and anion-exchange chromatography were concentrated, radiolabeled with 125I, and subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Autoradiography revealed a band which corresponded to a MW of 14,000 (representing four similar monomeric chains) and to the region from which chemoattractant activity could be detected in eluates from slices of unstained gels run in parallel. The biological activity of this hybridoma-derived lymphocyte chemoattractant was abolished by treatment with trypsin and neuraminidase but was unaffected by heating to 56 degrees C. We conclude that certain human T-T-cell hybridomas constitutively elaborate a lymphocyte chemoattractant that appears to be physicochemically identical to a previously described human lymphokine, lymphocyte chemoattractant factor.

A Proposed Model for the Accumulation of Helper /Inducer Lymphocytes in Sarcoidosis

The secretory products of lymphocytes, monocytes/macrophages, and fibroblasts are all instrumental in the pathogenesis of pulmonary sarcoidosis. In sarcoidosis, as in granulomatous leprosy, there appears to be a redistribution of a subset of thymusderived (T) lymphocytes, more specifically, a subset identified by the OKT4 (helper/ inducer) phenotype, from the blood to the target organ? Once there, these lymphocytes elaborate several important regulatory proteins (lymphokines) including interleukin2 (IL-2),. which promotes expansion of the lymphocyte pool; a monocyte chemoattractant factor which promotes granuloma formation; and a fibroblast-activating factor6 which promotes collagen synthesis. The mechanisms by which these circulating helper /inducer lymphocytes are recruited to inflammatory sites in lung parenchyma are unknown. Over the past several years, our laboratory has been investigating lymphocyte-derived factors which influence T cell motility. This monograph describes two lymphocyte subset-specific chemoattractant lymphokines and provides a model for helper/inducer lymphocyte accumulation in the lung.