Suppression of phagocytosis

Thus, saponins are apparently able to stimulate or suppress the immune system by two different mechanisms. In one mechanism, saponins interact with cell membrane components to alter cell permeability, membrane-associated enzymes, cell-surface receptors, and other components, and thus result in a nonspecific stimulation (or suppression) of phagocytosis, phagocytic chemiluminescence, and other functions of phagocytic lymphocytes. These effects can take place in vivo or in vitro. In the other mechanism, formation of imines (Schiff bases) by carbonyl-containing saponins can provide a co-stimulatory signal necessary for specific immunopotentiation of T cells that leads to a CMI response. This second mechanism, which is known as an adjuvant effect, takes place only in vivo, and is discussed in more detail in subsequent sections of this article. From previous work [62,73], it is expected that, for saponins with appropriate structures, both mechanisms would take place. Perhaps, the best-known case where both mechanisms can take place is that of the saponins derived from Q. saponaria Molina, which are next discussed in more detail. 

Secondary infections often occur when a primary pathogen reduces the immunological resistance of the patient, so that other microorganisms of limited pathogenicity produce disease [4]. For example, a primary viral infection may lead to a secondary bacterial infection. Staphylococcal pneumonia is rarely a primary disease, but is often observed as a sequel to viral influenza. This predisposition to a secondary infection is generally due to a stress disruption of both cellular and humoral immunity and a suppression of phagocytosis due to a distinct drop in the opsonization of antigen [5,6]. 

Matt, U., Sharif, O., Martins, R., Furtner, T., Langeberg, L., Gawish, R., Elbau, I. et aL 2013. WAVEl mediates suppression of phagocytosis by phospholipid-derived DAMPs. 123, 3014—3024. 

Matt, U., Sharif, O. and Martins, R. WAVEl mediates suppression of phagocytosis by... 

The phagocytic cells (macrophages of the liver and spleen) of the RES remove particulate systems (considered as foreign bodies). This process is facilitated by adsorption of proteins at the solid/liquid interlace, a process that is referred to as opsonization. Suppression of phagocytosis by other components of the blood, such as immunoglobin... 

Although bacterial clearance studies and models of infection are useful for showing how particle inhalation can alter host resistance to infection, analysis of cell type and function after in vivo or in vitro particle exposure can produce more detailed information about the molecular and cellular processes affected by the toxicant. Overall interpretation of these experiments is difficult because some studies show suppression of phagocytosis and downregulation of immune cytokines, whereas others indieate an increase in these functions, suggesting a state of activation. These eontradictory results can often be explained by differences in experimental protoeols and culture techniques, the endpoints under study, species from which the eells are derived, and the type of particle used. It is well to keep the old toxicology adage in mind, however, that the dose makes the poison, and that subtoxic concentrations of substances can often be beneficial or at least stimulatory. 

Szabo, I.et al., Suppression of peritoneal macrophage phagocytosis of Candida albicans by opioids, J. Pharmacol. Exp. Ther., 267, 703, 1993. 

With long-term treatment, IgG subclass deficiencies can become marked (312). There is suppression of the antigen-antibody reaction, and since this reaction itself normally results in liberation of kinins, the latter is also suppressed. Failure of kinin liberation leads in turn to inhibition of invasion of sensitized leukocytes and reduced production and maturation of phagocytes. Undoubtedly, it is true that using minimal effective doses will avoid the most serious consequences, but the problem cannot be fully circumvented, since the antiinflammatory effects themselves involve some inhibition of the migration of leukocytes and phagocytosis. 

Vernon-Roberts B, Jessop JD, Dore J. Effects of gold salts and prednisolone on inflammatory cells. II. Suppression of inflammation and phagocytosis in the rat. Ann Rheum Dis 1973 32 301-307. 

Several studies have demonstrated that MDMA can suppress neutrophil phagocytosis as well as suppress the production of tumor necrosis factor-alpha and interleukin. 

Numerous reviews have documented immune modulation in response to metal, pesticide and organic contaminants in fish4,19,37,135. Assays traditionally used to assess perturbations of immune function in fish fall into three broad categories pathogen challenge models, assays that monitor immune suppression/activation or immuno-pathology. Immune suppression/activation is usually measured with assays of phagocytosis, respiratory burst, cell proliferation, as well as quantification of soluble factors such as lysozyme, serum antibody, CRP or complement. 

Suppression of cellular immunity and inhibition of phagocytosis by steroids, including chronic use of inhaled and topical steroids. 

Phagocytosis of apoptotic cells by macrophages leads to the production of anti-inflammatory cytokines as a way of preventing inflammation. Kurosaka et al. [79] have demonstrated that human serum potentiates the production of two anti-inflammatory cytokines, IL-10 and TGF-J3, by both TPA-treated THP-1 cells and human monocyte-derived macrophages. This enhanced response to the presence of apoptotic cells also results in the suppression of the production of the pro-inflammatory cytokine IL-8. In addition, human IgG and FcyRI appear to be critical in triggering the production of anti-inflammatory cytokines by macrophages in response to apoptotic cells. 

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