ON THE CELLULAR FIXATION OF CYTOPHILIC ANTIBODY

STUDIES ON TUBERCULIN FEVER. 3. MECHANISMS INVOLVED IN THE RELEASE OF ENDOGENOUS PYROGEN IN VITRO

In a search for the source of the circulating endogenous pyrogen (EP) that mediates tuberculin-induced fever, tuberculin was incubated in vitro with various tissues of rabbits sensitized by intravenous infection with BCG. Evidence was obtained that tuberculin specifically stimulates cells in the blood of sensitized rabbits to generate pyrogen in vitro, whereas both lymph node and spleen cells from the same donors were inactive. Since normal blood cells, incubated in plasma of sensitized donors, were similarly activated, it is postulated that circulating antibodies play a role in sensitizing cells (presumably granulocytes) to release pyrogen on contact with tuberculin) both in vitro and in vivo. Release of endogenous pyrogen in vitro may be a sensitive means of detecting immunologic reactions between antigen and specifically sensitized blood cells-in other allergic states accompanied by fever.

Herpesviral Fc receptors and their relationship to the human Fc receptors

Nearly two decades ago, it was observed that cells infected with herpes simplex virus (HSV) acquired an IgG Fc binding activity. The properties of the viral Fc receptor (FcR) have now been characterized by several laboratories. The Fc binding activity appears on the surface of the infected cell prior to formation of progeny virions. The FcR induced by HSV has been identified as the HSV glycoprotein, gE. When HSV gE forms a complex with a second HSV glycoprotein, gI, the receptor binds IgG with higher affinity. Varicella-zoster virus (VZV), which is closely related to HSV, has also been shown to induce an FcR. Like the HSV FcR, the FcR specified by VZV possesses characteristics common to viral glycoproteins. VZV encodes two glycoproteins, gpI and gpIV, which are the homologs of HSV gE and gI. The VZV glycoproteins have many properties common to cell surface receptors, including O-linked glycans and phosphorylation sites. However, extensive computer-assisted analyses of the amino acid sequences of VZV gpI and gpIV did not uncover regions of homology to the human cellular Fc receptors for IgG.

Proteinase-induced modulation of the activity of rat macrophages to bind rabbit-IgG-sensitized sheep erythrocytes

Rat alveolar and peritoneal macrophages were tested in a rosetting assay for their capacity to bind rabbit IgG antibody sensitized sheep erythrocytes (EA) before and after various times of incubation with proteolytic enzymes. With most enzymes, a biphasic effect on EA rosette formation was observed: an initial enhancement was followed by a reduction of the number of rosette-forming cells (RFC). The extent and rate of these changes depended on the type and concentration of the enzyme and on the amount of IgG antibodies used to sensitize the sheep erythrocytes. At low enzyme concentrations and with lowly sensitized EA, the phase of RFC enhancement was more prominent and prolonged. With an increase of enzyme concentration, the rate of reduction of RFC was increased. With regard to different enzymes, the highest rate of receptor degradation was found with pronase, followed by trypsin, whereas alpha-chymotrypsin had little receptor-degrading activity. A slight enhancement not followed by a loss of EA-rosetting activity was induced by granulocyte elastase at the concentrations studied. The results may give an explanation to contradicting reports in the literature, in which a single dose or just a few doses of proteolytic enzymes were employed and no kinetic studies were performed. In addition, EA-rosette-inhibiting material was found in supernatants of macrophage cultures, suggesting that receptor-like material was shed during incubation in serum-free medium. This material lost its EA-rosette-inhibiting capacity after proteinase treatment.

Effect of proteinases on EA (IgG)-binding receptors of rat macrophages

Pronase, trypsin and delta-chymotrypsin deplete rat alveolar peritoneal macrophages of EA (IgG)-binding activity. Trypsin and delta-chymotrypsin show an initially--under certain conditions and lasting--enhancement of receptor activity. Cycloheximide, an inhibitor of protein biosynthesis, accelerated the loss of Fc-receptors and inhibited their reappearance. There are differences between alveolar and peritoneal macrophages in the rate of loss as well as of regeneration of Fc-receptors.

The characterization and functional significance of plasma membrane Fc Receptors

The importance of various components of the plasma membrane in the generation of the immune response has long been recognized. The identification and characterization of functional membrane receptors are essential for an understanding of the molecular basis of the immune response. The Fc receptor can be operationally defined as a site on the plasma membrane which is capable of binding the Fc portion of IgG. The Fc receptor has been reported on both lymphoid and nonlymphoid cell types. The functional significance of the receptor on these cell populations, as well as the biochemistry of the receptor, is not well established and is currently an important area of investigation. In this review, the Fc receptor will be discussed, primarily in human and murine lymphoid and macrophage cell populations, as a model of membrane immunoreceptors. The review will be divided into four sections. In the first section, consideration will be given to the binding assays used to study Fc receptor-ligand interactions and the class and subclass specificity of the receptor. The possibility of receptor-receptor interaction and quantitation of receptor sites will be discussed. The second phase of the review will be concerned with the fractionation and biochemistry of this receptor system, emphasizing the differences reported in receptor composition from different cell sources. In the third section of the review, the biologic significance of the receptor will be examined. The importance of the Fc receptor in opsonization and phagocytosis by mononuclear phagogytes, B-cell activation, antibody-dependent cell cytotoxicity, and the possible relationship of Fc receptors to the histocompatibility-linked immune response genes will be discussed. Finally, in the fourth section, the possible mechanisms of receptor regulation will be considered. Cell fusion experiments which have been performed and the expression of receptor activity on the hybrid cell clones will be discussed. Receptor regulation at the physiologic level will include the effects of cyclic nucleotide levels and cell cycle on receptor expression. It is the intent of this review to provide a detailed analysis of the Fc receptor and to emphasize its importance in microbiology, cell biology, and immunology.

Macrophage-cytophilic antibodies and the functions of macrophage-bound immunoglobulins

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Studies on tuberculin fever. IV. The passive transfer of reactivity with various tissues of sensitized donor rabbits

Utilizing techniques of passive transfer, we have investigated the factors responsible for production of fever when tuberculin is given intravenously to specifically sensitized rabbits. The ability to develop a febrile response to tuberculin could be passively transferred to normal recipients with viable mononuclear cells from peritoneal exudates, spleen, or lymph nodes of donor rabbits sensitized with BCG. Sensitivity was usually apparent 48 hr after transfer, maximal at 7 to 14 days, and rapidly declined thereafter. Granulocytes and nonviable, sonicated, mononuclear cells from similarly sensitized donors were unable to transfer this form of reactivity. Passive transfer of reactivity was also effected with plasma and serum, suggesting that the reaction of antibody with antigen contained in tuberculin is one of the initial steps by which the host cells are activated to release the endogenous pyrogen (EP) that mediates this form of hypersensitivity fever. An intravenous infusion of granulocytes, as well as of several types of mononuclear cells from sensitized donors, made most recipients responsive to the pyrogenic effect of old tuberculin (OT) given 2 hr later. Some of these passively transferred cells, such as the granulocyte and alveolar macrophage, may be activated in vivo by OT, as they are in vitro. However, in the case of splenic and lymph node cells that cannot be activated by OT to produce EP in vitro, it seems likely that an intravenous injection of OT causes these transferred, sensitized cells to liberate an intermediate substance that either directly, or in association with antigen, activates the host's normal cells to produce EP. In support of previous suggestions that leukocytes of several types, as well as phagocytic cells of the reticuloendothelial system, serve as potential sources of EP in tuberculin-induced fever, evidence was presented that OT also activates both granulocytes and mononuclear cells from sterile exudates of BCG-sensitized donors to produce EP in vitro.

Opsonizing and bactericidal activity of antibodies against common antigen of Enterobacteriaceae

Domingue, Gerald J. (State University of New York at Buffalo, Buffalo, N.Y.), and Erwin Neter. Opsonizing and bactericidal activity of antibodies against common antigen of Enterobacteriaceae. J. Bacteriol. 91:129-133. 1966.-In addition to the well-known O, H, K, and Vi antigens, Enterobacteriaceae produce a common antigen, which was first identified by hemagglutination tests with Escherichia coli O14 antiserum. Studies on the biological significance of this antigen by in vitro phagocytic experiments have revealed that opsonization is markedly enhanced in the presence of the corresponding antibody, rabbit polymorphonuclear leukocytes, and normal rabbit serum. This effect is specific, because Pseudomonas aeruginosa, which is devoid of this antigen, is not opsonized under these conditions, and removal of the antibody by absorption markedly reduces the uptake of enteric bacteria containing the antigen. Opsonization thus represents another method for the study of this antigen-antibody system. Bactericidal tests have revealed that antibodies against this antigen, engendered in rabbits by different strains of enteric bacteria and various procedures, are bactericidal for E. coli O14 but not for other enteric bacteria, possibly due to previously demonstrated differences between the antigen moieties obtained from these microorganisms.