Differential inhibition of histamine release from human basophils induced by antigen, anti-IgE or N-formyl-L-methionyl-L-leucyl-L-phenylalanine

We report differential effects of various compounds on inhibition of histamine release from washed leukocytes stimulated through IgE (using antigen or anti-IgE antibody) or N-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP) receptors. Inhibition of IgE-induced release was seen for several compounds listed in order of potency (IC50 in microM): CI-922 (3,7-dimethoxy-4-phenyl-N-(1-H-tetrazol-5-yl)-4-H-furo-[3, 2-b]-indole-2-carboxamide, 1-arginate) less than NDGA less than BW755c less than proxicromil less than isamoxole less than phenidone. Other compounds including FPL 55712, meclofenamate, and indomethacin were inactive or enhanced IgE-mediated release. When FMLP was used to stimulate histamine release the order of potency (IC50) changed: meclofenamate = FPL 55712 = proxicromil less than CI-922 less than NDGA = BW755c less than indomethacin less than isamoxole = phenidone. The inhibition of FMLP-induced histamine release by FPL 55712, meclofenamate and indomethacin in the absence of inhibition (or even enhancement) of histamine release by the IgE mechanism suggests that different pathways of activation and/or control are critical in the release process when different stimuli are used to activate basophils.

Failure of covalently cross-linked human IgG myeloma subclass protein to release histamine from human leukocytes

We have examined the ability of IgG subclass antibodies to release histamine from human leukocytes using covalently cross-linked oligomers of human myeloma proteins. Purified IgG1, G2, G3, G4, (or IgE) was incubated with dimethyl suberimidate to induce cross-linking. The resulting dimers, trimers, and higher molecular weight oligomers were isolated using gel filtration columns (Sephadex G200 and Ultrogel AcA 22) connected in tandem. None of the oligomers of IgG1, G2, G3, or G4 released histamine from leukocytes of donors whose basophils released histamine when challenged with IgE dimer. Furthermore, preincubation with subclass specific oligomers did not desensitize cells to challenge with IgE dimer or to anti-IgE. We conclude that, under our experimental conditions, oligomers of human IgG myeloma subclass antibodies do not trigger histamine release nor modulate IgE-mediated reactions.

Spontaneous, in vitro, malignant transformation of a basophil/mast cell line

It has recently become possible to grow basophil/mast cells in vitro for extended periods of time. Normally, these cultures remain fully dependent upon the presence of an adequate supply of growth factor(s) and the cells express several basophil/mast cell differentiated traits. We report here a case of spontaneous, in vitro, malignant transformation of such a basophil/mast cell line. The transformed cells no longer require the addition of growth factor(s) for continuous proliferation in vitro, and they have become highly tumorigenic in vivo. In contrast, when compared to their untransformed counterparts, they display the same set of differentiated traits, characteristic of immature basophil/mast cells. Thus, the data support the hypothesis that cell transformation results from a decreased sensitivity of precursor cells toward normal growth regulators but does not affect significantly the expression of differentiated functions.

Skin reactivity, basophil degranulation and IgE levels in ageing

Skin tests with histamine, the histamine-liberator, codeine, and various allergens as well as blood basophil degranulation by anti-IgE or anti-IgG4 and total serum IgE levels have been studied in two female populations of different ages (average 23.1 and 73.9 years). All thirty-one patients selected for this study were clinically non-allergic. We observed a trend towards reduced skin reactions to histamine and codeine in the higher age-group; on the other hand, we could not find any decrease of basophil degranulation as a sign of basophil impairment with age. Likewise no difference in total serum IgE levels have been noticed. No correlation between skin tests and basophil degranulation was observed; yet patients with isolated, positive skin tests to house dust and/or Candida albicans showed a statistically significant reduced blood basophil degranulation by anti-IgE or anti-IgG4.

Evaluation of 3H-histamine incorporation into human peripheral blood leukocytes

We have examined the use of 3H-histamine for evaluating in vitro basophil responses. Incubation of 3H-histamine for 4 h with basophil-enriched mononuclear fractions containing autologous plasma, resulted in the best incorporation of the label. Even so, less than 3% of the added label was actually recovered and other leukocytes also bound or incorporated 3H-histamine. Labeled mononuclear preparations failed to release 3H-histamine when challenged with zymosan-activated serum or anti-IgE, but endogenous histamine released under the same experimental conditions could be determined fluorometrically. The calcium ionophore, A23187, however, did cause a dose-dependent release of 3H-histamine. We conclude that 3H-histamine is not preferentially incorporated into basophil granules, and that this technique cannot be used for assessing allergen and/or IgE-mediated basophil responses.

[Urticarial skin reaction to codeine, a measure of mast cell reactivity]

The reactivity of skin mast cells was tested in 86 probands. Introduction of various concentrations of codeine phosphate, either by intradermal injection or by prick test, produced an immediate wheal and flare response. Since the codeine skin test depends on both release of and response to histamine, it may be more useful than the conventional skin test with histamine for assessment of skin reactivity, and also for preliminary evaluation of anti-allergic agents in man.

Passive sensitization of human basophils: evidence for heterogeneity in the IgE molecule

Possible functional heterogeneity of human IgE antibody was studied by passively sensitizing human basophils for antigen-induced histamine release. Six sera of known IgE anti-ragweed antigen E and total IgE content were diluted to contain 10 ng of antibody but differed with respect to the ratio of specific/total IgE. The relative ability of the sera to passively sensitize generally reflected the specific/total IgE ratio but one serum was 2.5 times more active than the remainder. This ability did not reflect the IgG antibody level nor was it due to a dialyzable or heat-stable factor. These data indicate functional IgE heterogeneity, probably due to the interaction of the Fc portion of IgE with the basophil receptor.

IgE receptors on human basophils. Relationship to serum IgE concentration

As reported previously, and confirmed here in 26 donors, the serum IgE level (2.6-5,500 ng/ml) correlates well (rs = 0.95, P less than 0.001) with the in vivo number of IgE molecules/basophil (6,000-600,000). The total number of IgE receptors/basophil was monitored by incubating them with an IgE-rich serum (15 microgram/ml), quantitatively stripping IgE from the cells at pH 3.7, and measuring eluted IgE by a direct radioimmunosorbent test. Saturation of receptors for each donor was achieved with 15 nM IgE (3 microgram/ml). The proportion of receptors occupied in vivo correlated with the serum IgE (rs = 0.84, P less than 0.001) whereas the average association constant of the receptors was independent of serum IgE and ranged from 7.1 X 10(8)/M to 2.8 X 10(10)/M, averaging 7.7 X 10(9)/M. Unexpectedly, the total number of IgE receptors/basophil was closely related to the serum IgE level. (rs = 0.92, P less than 0.001). Thus, either there is genetic association between serum IgE and the number of basophil IgE receptors, or, more likely, the receptor number is modulated by the serum IgE concentration.

Measurement of IgE on human basophils: relation to serum IgE and anti-IgE-induced histamine release

The number of IgE molecules bound to human basophils was calculated from direct measurements of the IgE dissociated after exposing leukocytes to pH 3.7 acetate buffer in the cold. In 18 donors studied, cell-bound IgE ranged from 4000 to 500,000 molecules/basophil and correlated with the serum IgE concentration (r = 0.89, p less than 0.001) which ranged from 5 to 3,000 ng/ml. Sensitivity of these cells to anti-IgE was tested to explore the relationship between cell-bound IgE and the concentration of anti-IgE required for histamine release. Cells from some nonatopic donors (4000 to 100,000 IgE molecules/basophil) were as sensitive as cells from allergic donors (100,00 to 500,000 IgE molecules/basophil). Moreover, cells from donors having approximately the same cell-bound IgE concentration varied widely in their sensitivity to anti-IgE. We conclude that an intrinsic property of human basophils ("releasability") is an important parameter in determing mediator release.

Release of slow reacting substance of anaphylaxis (SRS-A) from human leukocytes by the calcium ionophore A23187

The ability of the calcium ionophore A23187 to release slow reacting substance of anaphylaxis (SRA-A) from human leukocytes was studied. About 25 times more SRS-A activity was released from aliquots of leukocytes by ionophore stimulation than by antigen stimulation, although comparable amounts of histamine were released. Cell separation studies revealed that granulocytes other than basophils were also capable of releasing SRS-A. The contractile activity released after challenge with ionophore appeared physicochemically identical to the SRS-A of rat or human origin released by antigen challenge in terms of its stability to base hydrolysis, inactivation by arylsulfatase, and chromatographic behavior on silicic acid and Sephadex LH-20 columns. We suggest that some mediators of allergic reactions previously associated, in man, only with antigen-IgE antibody interaction on mast cells or basophils may be released by other stimuli and from other cell types.

Structural features and biologic properties of fragments obtained by limited proteolysis of C3

Limited proteolysis of the third component of human complement (C3) was performed by using trypsin and streptococcal proteinase and the digests were analyzed for biologic activity. Incubation of C3 with trypsin for 1 min yielded a peptide with smooth muscle-contracting activity but no chemotactic activity, whereas the digest obtained after 15 min of incubation had only chemotactic activity. The conversion of muscle contracting to chemotactic activity could be correlated with the time course of trypsin hydrolysis. Hydrolysis of C3 with streptococcal proteinase gave a digest demonstrating only chemotactic activity. Each digest was resolved on a Sephadex G-100 column and the fractions containing biologic activities were characterized. The amino acid composition of the trypsin fragments, despite having different biologic activities, was remarkably similar, although differences in NH2-terminal amino acids were demonstrable. The fragments obtained by digestion of C3 with the streptococcal proteinase had an amino acid composition different from the trypsin fragments and displayed marked heterogeneity of NH2-terminal residues. These results suggest that slight alterations in the primary structure of C3 fragments may yield significant changes in their biologic activities and that the structural requirements for chemotactic activity are not confined to a single peptide species.

Effects in the rat of intradermal injection of purified proteinases from streptococcus and Serratia marcescens

Purified streptococcal proteinase and Serratia proteinase are potent permeability factors in rat skin and initiate histopathological evidence of an acute inflammatory response. These effects appear to be largely independent of terminal components of complement, histamine, and polymorphonuclear leukocytes.

Generation by Bacterial Proteinases of Leukotactic Factors from Human Serum, and Human C3 and C5

Proteinases derived from Serratia marcescens and group A, β-hemolytic Streptococcus are each able to generate, by cleavage, leukotactic fragments from human C3 and C5. In whole human serum, the Serratia enzyme produces a C3-related leukotactic factor, while the streptococcal proteinase produces a C5-related factor. The finding that proteinases derived from bacteria are able to generate complement-dependent leukotactic factors suggests that this may be one mechanism by which bacteria incite and maintain inflammatory reactions in tissues.