Effect of C-reactive protein on peritoneal macrophages. I. Human C-reactive protein inhibits migration of guinea pig peritoneal macrophages

An overview on human serum lectins

An extensive literature survey done on the various naturally occurring lectins in human serum upon its salient features such as methods of detection, level and sites of synthesis, binding specificity, cation dependency, modes of isolation, molecular and functional characterization way back from 1930s to till date was presented in a tabulated section. In addition, the generation of lectin and other immune molecules in vertebrates upon treatment with exogenous elicitors has also been framed in a tabular form. Furthermore, ANEW lectin induced in human serum for the very first time by an exogenous elicitor was detected, isolated and characterized by us whose features are also tabulated explicitly.

Acute phase protein response to viral infection and vaccination

Organisms respond in multiple ways to microbial infections. Pathogen invasion tipically triggers an inflammatory response where acute phase proteins (APP) have a key role. Pentraxins (PTX) are a family of highly conserved APP that play a part in the host defense against infection. The larger proteins of the family are simply named pentraxins, while c-reactive proteins (CRP) and serum amyloid proteins (SAA, SAP) are known as short pentraxins. Although high APP levels have been broadly associated with bacterial infections, there is a growing body of evidence revealing increased PTX, CRP and SAP expression upon viral infection. Furthermore, CRP, PTX and SAP have shown their potential as diagnostic markers and predictors of disease outcome. Likewise, the measurement of APP levels can be valuable to determine the efficacy of antiviral therapies and vaccines. From the practical point of view, the ability of APP to reduce viral infectivity has been observed in several virus-host models. This has prompted investigation efforts to assess the role of acute phase response proteins as immunoregulatory molecules and their potential as therapeutic reagents. This work aims to present an overview of the APP response to viral infections reviewing the current knowledge in the field.

The Effect of C-Reactive Protein (CRP) on Respiratory Burst of Human Peripheral Blood Phagocytes

The effect of C-reactive protein (CRP) on the oxidative response of human peripheral blood monocytes and granulocytes was investigated. The respiratory burst of phagocytes induced by phorbol-myristate-13-acetate (PMA), phytohaemagglutinin (PHA) or opsonized zymosan (OZ) was measured in luminol-enhanced chemiluminescence.

The effect of CRP on PMA-induced monocyte chemiluminescence (CL) depended both on CRP concentration and incubation time. A short incubation of cells with CRP (15–30 min.) enhanced the oxidative burst. Preincubation of cells for 1h (or longer) with low doses of CRP (about 2 μg/ml) increased, while with higher (>10 μg/ml) inhibited PMA-stimulated chemiluminescence. CRP reduced also PHA or OZ-induced monocyte respiratory response. CRP diminished PMA, PHA, and OZ-induced granulocyte chemiluminescence, except the response to PHA in the presence of low doses CRP (about 5 μg/ml).

The action of CRP on phagocytes probably involves activation of some intracellular mechanisms. During immune response, CRP could protect tissues against damage by excess of free oxygen and its biological active derivatives.

Degradation of rat C-reactive protein by macrophages

Rat C-reactive protein (CRP) is a serum glycoprotein belonging to the 'pentraxin' family of proteins. In this study we have shown the specific binding of 125I-CRP to rat peritoneal macrophages at 4 degrees C. This binding was dependent upon incubation time, CRP and cell concentrations, and was not inhibited by either phosphorylcholine or human IgG. At 37 degrees C, the surface-bound 125I-CRP was internalized and degraded. The degradation of 125I-CRP was measured by the formation of 125I-labelled trichloroacetic-acid-soluble CRP peptides by either precipitation assays or by h.p.l.c. of the incubation medium using a gel-filtration column. Since chloroquine and leupeptin inhibited CRP degradation, it was concluded that degradation of CRP occurred in the lysosomal compartment of the macrophage. There was an absolute requirement for the presence of bivalent cations (Ca2+ and Mg2+) in the incubation medium for the binding and degradation of CRP, which could be inhibited by EDTA but not by phosphorylcholine or human IgG. H.p.l.c. analysis of the medium obtained from incubation of macrophages with 125I-CRP revealed the presence of 125I-labelled low-M(r) peptides, the formation of which was dependent upon incubation time.

Activation of macrophages by recombinant interferon-gamma has no effect on myelin phagocytosis but hinders invasion of nerves in organ culture

Myelin phagocytosis in nerves undergoing Wallerian degeneration was shown to depend on their invasion by non-resident, hematogenous macrophages. This process can be studied in vitro using organ cultures of peripheral nerves exposed to cultured peritoneal macrophages. The present report concerns the effect of recombinant interferon-gamma (rIFN-gamma) on luminol-dependent chemiluminescence, macrophage migration and myelin phagocytosis in organ cultures. Chemiluminescence was activated by rIFN-gamma compared to untreated cells. The macrophage population was capable of activation at any phase of exposure to organ cultures. The engagement of macrophages in myelin phagocytosis, however, varied with the timing of the application of rIFN-gamma. Application from the start of the experiment led to activation of chemiluminescence and also to a complete inhibition of macrophage invasion of the organ culture, thus preventing myelin removal. Application of rIFN-gamma at a later phase of the experiment had no effect on cell invasion and also no detectable effect on the efficiency of myelin phagocytosis. There was no indication that myelin phagocytosis by itself activated chemiluminescence in untreated cultures. Phagocytosis of myelin appears to be a function of macrophages independent of activation causing production of oxygen radicals.