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With a modified rat mast cell degranulation (RMCD) technique developed by Korotzer, Haddad and Lopapa (1971), the mechanism of mast cell degranulation by IgE-anti-IgE reaction and the inhibitory effect of cAMP-related compounds upon IgE-mediated mast cell degranulation were studied. Degranulations of 90 per cent or more were decreased to 13-16 per cent when the mast cells were pretreated with human IgE or normal human serum. However, if rat mast cells were pretreated with anti-human IgE rabbit serum or normal rabbit serum, the degranulation per cent in these cells by IgE-anti-IgE reaction was the same as in the nontreated cells. These results suggest the presence of receptors in rat mast cells for human IgE or normal human serum, and the lack of receptors in these cells for anti-human IgE rabbit serum or normal rabbit serum. Treatment of isolated rat mast cells with adenyl cyclase stimulating agents (isoprenaline, adrenaline, prostaglandin E1 and E2 and theophylline or amino-phylline, which inhibit the enzymatic degradation of cAMP, also inhibit the morphological degranulation of the mast cells. Cromoglycate or chlorophenes in derivatives, which might have a stabilizing effect of the cell membrane, also inhibited the degranulation of the rat mast cells mediated by IgE-anti-IgE reaction. These results support the attractive hypothesis that cAMP occupies a central modulatory role in the in vitro mast cell degranulation in IgE-anti-IgE reaction. [ABSTRACT FROM AUTHOR]

The surface characteristics of the mouse spleen cells mediating antibody-dependent cytotoxicity (ADCC) against antigen-coated chicken erythrocytes have been studied by several different column fractionation methods. The major effector cells in this system were shown to be surface-adherent and could be depleted from spleen cells by passage through glass-bead ovalbumin/anti-OA immune complex columns (Fc receptor-binding), glass-bead immunoglobulin/anti-mouse Ig columns (Fc receptor- and surface immunoglobulin-binding), and glass-bead mouse Ig/rabbit (Fab')2-anti-mouse Ig or Sephadex G-200/rabbit anti-mouse Ig columns (surface immunoglobulin-binding). The concentration of EDTA in the medium used to fractionate the cells played a significant role in determining whether surface immunoglobulin could be demonstrated on the ADCC effector cells. From these results, the conclusion was drawn that ADCC on the part of mouse spleen cells could be mediated by surface-adherent, Fc receptor-positive cells bearing surface immonoglobulin of unknown origin. The possibility that ADCC can be mediated by a heterogenous population of cells in the mouse spleen is discussed. [ABSTRACT FROM AUTHOR]

We present data concerning the mechanism of the binding of aggregated IgG and of IgG-sensitized erythrocytes by different human lymphocyte-like cells. The results showed that the two phenomena are related to different subpopulations of lymphocytes. By fractionation and depletion studies of B lymphocytes, T lymphocytes, and lymphocyte-like cells binding IgG-sensitized erythrocytes (EA-RFC), it was demonstrated that binding of aggregated IgG is related to B lymphocytes, whereas binding of IgG-sensitized erythrocytes depends on another subpopulation of lymphocyte-like cells. Whereas binding of IgG-sensitized erythrocytes by EA-RECs depends entirely on the Fc fragment, binding studies with IgG fragments suggested that the interaction of aggregated IgG with B lymphocytes is different. [ABSTRACT FROM AUTHOR]

BALB/c spleen cells were stimulated with C57B1/6 cells, keyhole limpet haemocyanin (KLH), pokeweed mitogen (PWM) or phytohaemagglutinin (PHA). By the immunofluorescence method the development of transformed cells with immunoglobulin-like receptor molecules or theta antigen was investigated. Transformed Ig-receptor cells were predominant after stimulation with KLH, followed by PWM, PHA and allogeneic cells in decreasing order. Transformed cells with theta-antigen were clearly increased after stimulation with allogeneic cells. With all systems, more transformed cells with Ig-receptors were found in the stimulated cultures than in the control cultures, indicating that all stimulants have an effect on both cell types. The implications of the results on the immunologic interpretation of results obtained by in vitro stimulation of lymphocytes with the different stimulants are discussed. [ABSTRACT FROM AUTHOR]

An α-2-glycoprotein from bovine serum (Fraction C) with immunosuppressive properties in vivo and anti-proliferative activity in vitro has been shown to reversibly inhibit the synthesis of cell surface receptors in vitro. The proliferative response of human lymphocytes in vitro to PHA and PPD can be inhibited by prolonged preincubation with Fraction C, which also inhibits the ability of lymphoid cells to bind PHA, 3-4 days for 90 per cent inhibition, and anti-immunoglobulin, 10 hours for 90 per cent inhibition. This inhibition is reversible and the binding ability recovers after removal of Fraction C at a similar rate to that at which it declined. Fraction C also rapidly and reversibly inhibits the secretion of antibody by immune spleen cells in vitro. The anti-proliferative effect of Fraction C is shown to involve an effect on ribosomal RNA synthesis and it is suggested that the mechanism of this action depends on the inhibition of protein synthesis, probably mediated by an effect on newly synthesized messenger RNA. The demonstration of different turnover rates of cell surface components on different types of cells suggests that it may be possible to use Fraction C to affect responsiveness of one type of lymphocyte while leaving another type unaffected. [ABSTRACT FROM AUTHOR]

Active uptake of sheep and chicken erythrocytes onto the surfaces of cockroach phagocytic haemocytes has been demonstrated to occur in vitro in the absence of haemolymph. Haemocytes were treated with various enzymes and chemicals in attempts to elucidate the nature of the receptor site for vertebrate erythrocytes. Uptake was abolished by pretreatrnent of haemocytes with trypsin and not restored by incubation in haemolymph. No opsonic activity was demonstrable for cockroach haemolymph regarding uptake of vertebrate erythrocytes. Cockroach haemocytes do not possess a receptor site for γ-globulin on their surfaces. [ABSTRACT FROM AUTHOR]

The distribution in the mouse of lymphoid cells carrying receptors for IgG or IgG-Ag was investigated. B lymphocytes were found to have receptors reacting with both IgG and IgG-Ag. Resting T lymphocytes did not react with IgG-Ag. T lymphocytes activated by passage through irradiated, allogeneic mice had a receptor reacting with IgG-Ag, but not with IgG. [ABSTRACT FROM AUTHOR]

This study revealed the absence of muscle spindles and the presence of leaf-like receptors in the frog's geniohyoid muscle. The response pattern was studied during sinusoidal stretching of the muscle. Results are compared with the response patterns of two kinds of stretch receptors in the sartorius muscle. [ABSTRACT FROM AUTHOR]