Clinical efficacy of topical docosanol 10% cream for herpes simplex labialis: A multicenter, randomized, placebo-controlled trial

BACKGROUND

Recurrent herpes simplex labialis (HSL) occurs in 20% to 40% of the US population. Although the disease is self-limiting in persons with a healthy immune response, patients seek treatment because of the discomfort and visibility of a recurrent lesion.

OBJECTIVE

Our purpose was to determine whether docosanol 10% cream (docosanol) is efficacious compared with placebo for the topical treatment of episodes of acute HSL.

METHODS

Two identical double-blind, placebo-controlled studies were conducted at a total of 21 sites. Otherwise healthy adults, with documented histories of HSL, were randomized to receive either docosanol or polyethylene glycol placebo and initiated therapy in the prodrome or erythema stage of an episode. Treatment was administered 5 times daily until healing occurred (ie, the crust fell off spontaneously or there was no longer evidence of an active lesion) with twice-daily visits.

RESULTS

The median time to healing in the 370 docosanol-treated patients was 4.1 days, 18 hours shorter than observed in the 367 placebo-treated patients (P =.008; 95% confidence interval [CI]: 2, 22). The docosanol group also exhibited reduced times from treatment initiation to (1) cessation of pain and all other symptoms (itching, burning, and/or tingling; P =.002; 95% CI: 3, 16.5); (2) complete healing of classic lesions (P =.023; 95% CI: 1, 24.5); and (3) cessation of the ulcer or soft crust stage of classic lesions (P <.001; 95% CI: 8, 25). Aborted episodes were experienced by 40% of the docosanol recipients versus 34% of placebo recipients (P =.109; 95% CI for odds ratio: 0.95, 1.73). Adverse experiences with docosanol were mild and similar to those with placebo.

CONCLUSION

Docosanol applied 5 times daily is safe and effective in the treatment of recurrent HSL. Differences in healing time compared favorably with those reported for the only treatment of HSL that has been approved by the Food and Drug Administration.

The antiviral drug docosanol as a treatment for Kaposi's sarcoma lesions in HIV type 1-infected patients: a pilot clinical study

Docosanol inhibits a broad spectrum of lipid-enveloped viruses in vitro including HSV-1, HSV-2, VZV, CMV, HHV-6, and HIV-1. These observations led us to conduct a pilot clinical study with docosanol 10% cream as a topical treatment for Kaposi's sarcoma (KS) in HIV-1-infected patients. In this open-label study 28 cutaneous KS lesions in 10 HIV-1-infected patients were treated topically five times daily for 4 weeks with evaluation of lesion characteristics of area, edema, and color. All patients elected to enroll in an extended treatment protocol and continued to treat for up to 35 weeks. Within 28 days, 2 of 10 patients exhibited a partial response based on standardized criteria exhibiting 74 to 83% reductions in total target lesion areas. With extended treatment, a partial response was exhibited in two additional patients where total target lesion area was reduced by 52% in one patient and target lesions in another patient that had been large, swollen, and painful at study initiation were no longer visible. No patient experienced disease progression or signs of visceral disease. The average percent decrease in lesion area for all target lesions was 20% (p < 0.01). A patient's response to therapy appeared to be independent of anti-HIV regimen, HIV viral load, or previous KS treatments. These results suggest that docosanol merits further investigation as a potential topical therapy in the treatment of AIDS-associated Kaposi's sarcoma lesions.

Topical application of docosanol- or stearic acid-containing creams reduces severity of phenol burn wounds in mice

Because of their reported antiviral and anti-inflammatory activities, cream formulations containing n-docosanol (docosanol) or stearic acid were tested for effects on chemically-induced burns in mice. In this model, injury was induced by painting the abdomens of mice with a chloroform solution of phenol. This was followed by the topical application of test substances 0.5, 3, and 6 h later. Progression of the wounds was assessed by a single evaluator after 8 h, using a numerical score of gross morphology. Docosanol- and stearic acid-containing creams substantially and reproducibly lessened the severity and progression of skin lesions compared to untreated sites with a 76% and 57% reduction in mean lesion scores, respectively. Untreated wounds appeared red and ulcerated; docosanol cream-treated wounds showed only slight erythema.

The anti-herpes simplex virus activity of n-docosanol includes inhibition of the viral entry process

n-Docosanol-treated cells resist infection by a variety of lipid-enveloped viruses including the herpesviruses. Previous studies of the mechanism of action demonstrated that n-docosanol inhibits an event prior to the expression of intermediate early gene products but subsequent to HSV attachment. The studies reported here indicate that n-docosanol inhibits fusion of the HSV envelope with the plasma membrane. Evidence suggests that antiviral activity requires a time-dependent metabolic conversion of the compound. Cellular resistance to infection declines after removal of the drug with a t1/2 of approximately 3 h. Reduced expression of viral genes in n-docosanol-treated cells was confirmed by a 70% reduction in expression of a reporter gene regulated by a constitutive promoter inserted into the viral genome. Inhibited release in treated cells of virion-associated regulatory proteins--an immediate post entry event--was indicated by a 75% reduction in the expression of beta-galactosidase in target cells carrying a stably transfected lacZ gene under control of an HSV immediate--early promoter. Finally, the fusion-dependent dequenching of a lipophilic fluorescent probe, octadecyl rhodamine B chloride, inserted into the HSV envelope was significantly inhibited in treated cells. Inhibition of fusion between the plasma membrane and the HSV envelope, and the subsequent lack of replicative events, may be the predominant mechanism for the anti-HSV activity of n-docosanol.

Analysis of the promoter elements necessary for IL-4 and anti-CD40 antibody induction of murine Fc epsilon RII (CD23): comparison with the germline epsilon promoter

IL-4 and CD40 ligand stimulate transcription of CD23 (Fc epsilonRII) in B cells and are necessary for the expression of germline epsilon mRNA and production of IgE. Because in vivo studies have shown that the Fc epsilonRII is involved in the regulation of IgE, a study was initiated to compare how IL-4 and engagement of CD40 up-regulate the Fc epsilonRII and epsilon genes. Herein, we describe the preparation of a series of linker-scanning mutants that cover the IL-4 response region in the murine Fc epsilonRII promoter, and their function when transfected into M12.4.5 and M12.4.1 B lymphoma cell lines. Several discrete elements were found to be necessary for IL-4 induction of the Fc epsilonRII gene, some of which have homology with the binding sites of known transcription factors, including NF-IL-4 and NF-kappaB. In contrast, the response element for anti-CD40 (plus IL-4) mapped to a single discrete sequence, a NF-kappaB-like site. Aligning the Fc epsilonRII and germline epsilon promoters in the region that is highly conserved between the human and mouse homologues of both genes reveals a high degree of identity, particularly within discrete clusters. Comparing the function of linker-scanning mutants of the Fc epsilonRII promoter with a similar report for germline epsilon shows that both genes require at least two homologous and similarly located DNA elements in their promoters for a full IL-4 induction. Moreover, the similar response of Fc epsilonRII and epsilon promoter-driven chloramphenicol acetyl transferase plasmids to several cytokines and other agents suggests that the two proximal promoter regions are activated by a similar cassette of factors.

Analysis of the promoter elements necessary for IL-4 and anti-CD40 antibody induction of murine Fc epsilon RII (CD23): comparison with the germline epsilon promoter

IL-4 and CD40 ligand stimulate transcription of CD23 (Fc epsilonRII) in B cells and are necessary for the expression of germline epsilon mRNA and production of IgE. Because in vivo studies have shown that the Fc epsilonRII is involved in the regulation of IgE, a study was initiated to compare how IL-4 and engagement of CD40 up-regulate the Fc epsilonRII and epsilon genes. Herein, we describe the preparation of a series of linker-scanning mutants that cover the IL-4 response region in the murine Fc epsilonRII promoter, and their function when transfected into M12.4.5 and M12.4.1 B lymphoma cell lines. Several discrete elements were found to be necessary for IL-4 induction of the Fc epsilonRII gene, some of which have homology with the binding sites of known transcription factors, including NF-IL-4 and NF-kappaB. In contrast, the response element for anti-CD40 (plus IL-4) mapped to a single discrete sequence, a NF-kappaB-like site. Aligning the Fc epsilonRII and germline epsilon promoters in the region that is highly conserved between the human and mouse homologues of both genes reveals a high degree of identity, particularly within discrete clusters. Comparing the function of linker-scanning mutants of the Fc epsilonRII promoter with a similar report for germline epsilon shows that both genes require at least two homologous and similarly located DNA elements in their promoters for a full IL-4 induction. Moreover, the similar response of Fc epsilonRII and epsilon promoter-driven chloramphenicol acetyl transferase plasmids to several cytokines and other agents suggests that the two proximal promoter regions are activated by a similar cassette of factors.

n-Docosanol 10% cream in the treatment of recurrent herpes labialis: a randomised, double-blind, placebo-controlled study

n-Docosanol has been shown to have antiviral activity. To demonstrate the efficacy of n-docosanol 10% cream in the treatment of recurrent herpes labialis, a randomised, double-blind, parallel group, placebo-controlled study was undertaken in 63 patients. In a crossover extension, 22 of the patients used the alternative treatment for a further episode. A total of 98 episodes were evaluated. Application of n-docosanol 10% cream early in the prodromal or erythema stage of a recurrent episode of herpes labialis shortened mean healing time by approximately 3 days, as compared to late treatment with n-docosanol 10% cream and early or late treatment with the placebo. The crossover study revealed that late treatment with n-docosanol 10% cream significantly reduced mean healing time compared to placebo. Treatments were well tolerated.

Anti-herpes simplex virus activity of n-docosanol correlates with intracellular metabolic conversion of the drug

The 22-carbon fatty alcohol, n-docosanol, exhibits in vitro antiviral activity against several lipid-enveloped viruses including herpes simplex viruses 1 and 2 by a mechanism that interferes with normal viral entry into target cells. We previously reported that mammalian cells incorporate significant quantities of radiolabeled n-docosanol. Herein, we report that cells extensively metabolize the internalized fatty alcohol. This is evidenced by incorporation of up to 60% of cell-associated radiolabel into phospholipids that copurify with phosphatidylcholine and phosphatidylethanolamine. Analysis by chemical (Vitride) reduction suggests that a significant portion of n-docosanol is oxidized to n-docosanoic acid and then incorporated as an acyl group on polar lipids. A measurable amount of radiolabel, however, is resistant to Vitride reduction, consistent with incorporation of n-docosanol into ether lipids. The rate and extent of metabolic conversion of n-docosanol vary with the cell type and surfactant used to suspend the compound. Furthermore, the anti-HSV activity of n-docosanol is quantitatively proportional to the amount of metabolism observed. These findings suggest that the anti-HSV activity of n-docosanol involves cellular uptake and metabolism of the drug.

IL-10 stimulates murine antigen-driven antibody responses in vitro by regulating helper cell subset participation

The effects of IL-10 on in vitro antigen-driven murine antibody responses and helper cell IL-4 and IFN-gamma secretory capacity were investigated. Low antigen concentrations stimulated high responses in all antibody isotypes examined; IgD was not assayed. Under these conditions, exogenous IL-10 minimally potentiated synthesis of antigen-specific IgM, IgG1, IgG2a, IgG2b, IgG3, and IgA, but inhibited antigen-specific IgE secretion. High antigen levels stimulated antigen-specific IgM, IgG2a, and IgG2b responses, but inhibited synthesis of all other isotypes. In high antigen cultures, IL-10 augmented secretion of antigen-specific antibody in all isotypes except IgE. Essentially all of the antibody produced in the presence of high or low antigen concentrations was antigen-specific. Exogenous IL-10 substantially stimulated production of antigen-nonspecific antibody in all isotypes except IgG3. IL-10 allowed for greater Ig+ cell yield; comparable numbers of CD4+ and CD8+ cells were observed in the presence or absence of IL-10 in culture. The stimulatory effects of IL-10 for in vitro antibody responses were observed during a limited period of time after in vivo antigen priming of the responding cell populations. In contrast, IL-10 inhibited IgE synthesis at all time points tested. Low concentrations of antigen maintained the in vitro capacity of helper cells to secrete IL-4, while high antigen concentrations did not. Exogenous IL-10 potentiated IL-4 secretory capacity in high antigen cultures. The capacity for IFN-gamma secretion was comparable in high and low antigen cultures and exogenous IL-10 significantly inhibited such capacity under both sets of conditions. We conclude that IL-10 is generally stimulatory for murine antibody responses in vitro, with the possible exception of antigen-specific IgE. Such stimulatory effects appear to reflect increased activity of type 2 helper cells with concurrent decrease in type 1 helper cell activity.

Regulation of the murine Fc epsilon RII (CD23) gene. Functional characterization of an IL-4 enhancer element

The murine B cell IgE receptor (Fc epsilon RII, CD23) has been implicated in various functions including IgE regulation, Ag presentation, and B cell differentiation/activation. We have undertaken a series of studies to identify promoter sequences that are important for the constitutive and IL-4-induced expression of the murine Fc epsilon RII in M12.4.5 B lymphoma cells. By use of RNase protection analysis it was established that murine splenic B cells and M12.4.5 cells predominantly express the Fc epsilon RIIa form and that this receptor subtype accounts for the vast majority of IL-4-induced Fc epsilon RII mRNA in B cells. A 101-bp segment of the murine Fc epsilon RII proximal promoter coupled to a heterologous SV40 promoter was found to impart IL-4 inducibility in reporter assays. Removal of either 10 bp from the 5' end or 17 bp from the 3' end of this 101-bp fragment substantially reduced the IL-4 response. Both of these terminal deletions removed sequences that share homology with established IL-4 response elements of MHC class II and Ig (gamma 1 and epsilon) heavy chain genes. In addition, near the center of this 101-bp fragment lies a sequence that is highly homologous with NF-kappa B/LPS response elements previously identified upstream of the A alpha gene. DNA fragments containing this sequence together with one of the putative IL-4 response elements were able to impart a small LPS/IL-4 response in M12.4.5 cells. These results suggest that IL-4 and LPS induction of murine B cell Fc epsilon RII expression is mediated by a complex of transcription factors.

Regulation of the murine Fc epsilon RII (CD23) gene. Functional characterization of an IL-4 enhancer element

The murine B cell IgE receptor (Fc epsilon RII, CD23) has been implicated in various functions including IgE regulation, Ag presentation, and B cell differentiation/activation. We have undertaken a series of studies to identify promoter sequences that are important for the constitutive and IL-4-induced expression of the murine Fc epsilon RII in M12.4.5 B lymphoma cells. By use of RNase protection analysis it was established that murine splenic B cells and M12.4.5 cells predominantly express the Fc epsilon RIIa form and that this receptor subtype accounts for the vast majority of IL-4-induced Fc epsilon RII mRNA in B cells. A 101-bp segment of the murine Fc epsilon RII proximal promoter coupled to a heterologous SV40 promoter was found to impart IL-4 inducibility in reporter assays. Removal of either 10 bp from the 5' end or 17 bp from the 3' end of this 101-bp fragment substantially reduced the IL-4 response. Both of these terminal deletions removed sequences that share homology with established IL-4 response elements of MHC class II and Ig (gamma 1 and epsilon) heavy chain genes. In addition, near the center of this 101-bp fragment lies a sequence that is highly homologous with NF-kappa B/LPS response elements previously identified upstream of the A alpha gene. DNA fragments containing this sequence together with one of the putative IL-4 response elements were able to impart a small LPS/IL-4 response in M12.4.5 cells. These results suggest that IL-4 and LPS induction of murine B cell Fc epsilon RII expression is mediated by a complex of transcription factors.

Identification of a T cell membrane protein possibly involved in IL-4-induced B cell immunoglobulin class switching to IgE

The murine T cell hybridoma line, MBI-1.15, secretes a 17-kDa protein which decreases binding activity of the CD23 molecule for its natural ligand, IgE. This protein, denoted epsilon receptor-modulating protein (epsilon RMP), was previously characterized and shown to be a novel serine protease. The present studies show that, in addition to modulating CD23, epsilon RMP costimulates with IL-4 the de novo synthesis and secretion of IgE and IgG 1 by cultured B cells. Since such costimulating activity is reminiscent of a similar synergism with IL-4 previously observed with cell membranes from activated T cells, we examined isolated membranes from the epsilon RMP-producing MBI-1.15 T cell line for comparable activity; indeed, as shown herein, MBI-1.15 cell membranes do exhibit this synergism. Furthermore, we show that a monoclonal antibody (mAb), 2E5B, specific for the 17-kDa soluble form of epsilon RMP, blocks the costimulating activities of both the soluble epsilon RMP and MBI-1.15 T cell membranes for IL-4-induced de novo synthesis of IgE by cultured B cells. This anti-epsilon RMP mAb also detects a 36-kDa membrane-bound protein species which appears to be related to soluble epsilon RMP by immunochemical criteria. The membrane-bound proteins, present on MBI-1.15 T cells, induce germ-line IgE heavy chain transcripts (I epsilon) in I-29 B cells independently of IL-4, and this inductive event is also specifically blocked by the 2E5B anti-epsilon RMP mAb. These findings suggest that T cell membrane-bound epsilon RMP molecules are crucial proteins involved in contact-dependent B cell class switching in the course of IgE biosynthesis. Finally, both IL-4 and epsilon RMP induce I epsilon on I-29 B cells, but neither molecule by itself can induce class switching to IgE synthesis by splenic B cells. This clearly suggests that both epsilon RMP and IL-4 have another important molecular effect (which may or may not be identical) on B cells, that is essential for class switching, but only when both molecules are present simultaneously is the complete mechanism of class switching manifested.

Biphasic effect of kallikrein on IgE and IgG1 syntheses by LPS/IL-4-stimulated B cells

epsilon receptor modulating protein (epsilon RMP) was identified and purified in our previous studies as a murine T cell-derived soluble 17-kDa chymotryptic serine protease which suppresses avidity of binding between IgE and CD23 (low affinity Fc receptor for IgE) without decreasing the quantitative expression of the CD23 molecule. Some, but not all, of the other known soluble serine proteases showed epsilon RMP-like CD23-modulating activities. Further studies indicated that epsilon RMP exists not only as a soluble protein but also as a 36-kDa T-cell surface form. Both soluble and membrane-bound epsilon RMP can induce purified splenic B cells to secrete IgE in the presence of IL-4 even without lipopolysaccharide (LPS). In this study, therefore, we have tested effects of several known serine proteases on Ig production in vitro and have found that: (i) coculture of splenic B cells in the presence of LPS and IL-4 with serine proteases which have epsilon RMP-like substrate specificity, such as kallikrein and alpha-chymotrypsin, results in a significant increase of IgG1 and a slight increase of IgE secretion at low concentrations, and significant suppression at high concentrations in an isotype-selective manner; and (ii) the effects of these proteases are blocked by phenylmethylsulfonyl fluoride but not by indomethacin, suggesting that serine protease activity but not prostaglandin E2 is involved. The biological significance of the possible involvement of serine proteases on Ig class switching is discussed.

Antigen concentration determines helper T cell subset participation in IgE antibody responses

A recently developed in vitro system for antigen-stimulated primary and secondary murine IgE antibody responses has been used to define (a) the relative participation of the Th1 and Th2 cell-derived lymphokines IFN-gamma and IL-4, respectively, in such responses, and (b) the role of antigen concentration in determining functional helper T cell activity. These studies confirm that IL-4 and IFN-gamma exert regulatory effects on IgE synthesis, but the nature and extent of their respective effects on primary and secondary IgE responses differ. Thus, primary IgE responses are considerably more sensitive to and dependent on IL-4 than are secondary IgE responses since (1) anti-IL-4 monoclonal antibody totally inhibited primary IgE responses, but only partially affected secondary responses; and (2) exogenously added IL-4 could stimulate primary IgE responses to optimal antigen concentrations, but had no effect on secondary IgE production. Likewise, antigen-stimulated primary IgE responses are about eightfold more sensitive than are secondary responses to the inhibitory effects of IFN-gamma. Studying the effect of antigen dose on the quantity of IgE antibody produced revealed that although IFN-gamma could be detected by ELISA in cultures exhibiting high-dose antigen-dependent diminution of IgE production, anti-IFN-gamma monoclonal antibody could not reverse this phenomenon. Thus, IFN-gamma is not solely responsible for decreased IgE synthesis associated with high-dose antigen exposure. IL-4 activity was detected in the fluid from cultures stimulated with low, but not high, levels of antigen. Moreover, addition of exogenous IL-4 restored IgE production to normal levels in cultures exposed to high antigen concentrations. Therefore, it appears that high levels of antigen result in selective stimulation of Th1 cells which produce IFN-gamma, and diminished activation of IL-4-producing Th2 cells. These results help explain observations regarding the influence of antigen dose on the generation of experimental and clinical IgE antibody responses in vivo.

B cell sensitivity to IgE-suppressive activity of IFN-gamma is polymorphic and controlled by a non-H-2-linked gene

It has been suggested that at least two distinct genetic factors are involved in developing atopic diseases. One is the major histocompatibility complex which controls antigen-specific polymorphism of IgE antibody responses and the other is an unidentified factor(s) which controls isotype selection, i.e., class switching to IgE. It is conceivable that both expression of and sensitivity to lymphokines that play central roles in controlling IgE biosynthesis may be involved in the latter polymorphism. To explore this possibility, we have examined the sensitivities of several mouse strains to interleukin (IL)-4 and interferon-gamma (IFN-gamma). The results show that (1) the sensitivity to IgE-suppressive activity of IFN-gamma, but not to the IgE-enhancing activity of IL-4, is polymorphic (e.g., C57BL/6 is 8- to 16-fold more sensitive than BALB/c to IFN-gamma); (2) F1 of these two strains (CByB6F1) are BALB/c type and H-2 congenic mice of d haplotype with B6 background are C57BL/6 type, suggesting that low sensitivity is a non-H-2-linked dominant trait; (3) the polymorphism is determined at B cell levels; and (4) sensitivity to IFN-gamma is not associated with mRNA expression of IFN-gamma receptors (R) by B cells. These data collectively indicate that BALB/c mice have a non-H-2-linked gene which decreases B cell sensitivity to IFN-gamma, but the gene effect is not associated with the expression of IFN-gamma R mRNA on B cells. The possible biological significance of the non-H-2-linked gene is discussed.

B cell activator. Effects on B cell expression of CD23, proliferation, and antibody secretion

The studies herein describe a B cell hybridoma-derived, low m.w. (less than 1000 Da), hydrophilic mediator denoted B cell activator (BCA). BCA stimulates B cell expression of IgE-specific FcR (Fc epsilon RII or CD23) in a manner similar to IL-4. However, BCA can be readily distinguished from IL-4 because it does not 1) enhance B cell Ia expression; 2) bind 11B11 anti-IL-4 mAb; or 3) elicit superinduction of Fc epsilon RII expression or IgE production in cultures of LPS-activated B cells. Moreover, BCA is considerably more mitogenic than IL-4 for LPS-activated B cells and, in contrast to IL-4, lacks mitogenicity for anti-mu-activated B cells. BCA can enhance IgG2b and IgG3 production by LPS-activated B cells, responses that are suppressed by IL-4. BCA alone did not stimulate IgE and IgG1 production by LPS-activated B cells, but exerted synergistic activity when combined with IL-4 in stimulating secretion of these antibody isotypes. Finally, secondary Ag-driven IgG1, IgE, and IgA antibody responses can be stimulated by BCA in vitro. Thus, BCA appears to be a novel mediator with broad B cell activation properties.

B cell activator. Effects on B cell expression of CD23, proliferation, and antibody secretion

The studies herein describe a B cell hybridoma-derived, low m.w. (less than 1000 Da), hydrophilic mediator denoted B cell activator (BCA). BCA stimulates B cell expression of IgE-specific FcR (Fc epsilon RII or CD23) in a manner similar to IL-4. However, BCA can be readily distinguished from IL-4 because it does not 1) enhance B cell Ia expression; 2) bind 11B11 anti-IL-4 mAb; or 3) elicit superinduction of Fc epsilon RII expression or IgE production in cultures of LPS-activated B cells. Moreover, BCA is considerably more mitogenic than IL-4 for LPS-activated B cells and, in contrast to IL-4, lacks mitogenicity for anti-mu-activated B cells. BCA can enhance IgG2b and IgG3 production by LPS-activated B cells, responses that are suppressed by IL-4. BCA alone did not stimulate IgE and IgG1 production by LPS-activated B cells, but exerted synergistic activity when combined with IL-4 in stimulating secretion of these antibody isotypes. Finally, secondary Ag-driven IgG1, IgE, and IgA antibody responses can be stimulated by BCA in vitro. Thus, BCA appears to be a novel mediator with broad B cell activation properties.

Collagen-induced arthritis in mice. Relationship of collagen-specific and total IgE synthesis to disease

The relationship between production of IgE and collagen-induced arthritis in mice was examined. Collagen-specific IgE was produced as a consequence of immunization of DBA/1 mice with chicken type II collagen emulsified in CFA. We observed a rise in collagen-specific IgE antibody levels at the onset of CIA clinical and histologic signs in DBA/1 mice. This rise in IgE paralleled that of IgG2a anticollagen antibodies, an isotype implicated in the pathogenesis of CIA by other laboratories. The collagen-specific IgE contained in the plasma of mice with CIA could arm basophils for Ag- (collagen) dependent degranulation. Collagen-specific IgE may thus contribute to CIA by promoting mast cell degranulation in the synovia of susceptible mice immunized with chick type II collagen; but, further work is required to establish such a role for IgE in CIA. However, genetic differences in disease susceptibility could not be accounted for by quantitative differences in collagen-specific IgE production. Further, comparable levels of IgE anticollagen antibodies were observed in animals with active CIA and after spontaneous remission, thereby confirming that the presence of such antibodies is insufficient for disease. Total IgE levels peaked just before spontaneous remission indicating active production of IL-4. IL-4 was administered to animals with CIA to determine if this lymphokine could be involved in the remission process. IL-4 facilitated remission of CIA. Enhanced total IgE production may thus be a marker for activation of Th2 cells that produce lymphokines such as IL-4 and IL-10, factors that may be involved in the spontaneous remission process.

Collagen-induced arthritis in mice. Relationship of collagen-specific and total IgE synthesis to disease

The relationship between production of IgE and collagen-induced arthritis in mice was examined. Collagen-specific IgE was produced as a consequence of immunization of DBA/1 mice with chicken type II collagen emulsified in CFA. We observed a rise in collagen-specific IgE antibody levels at the onset of CIA clinical and histologic signs in DBA/1 mice. This rise in IgE paralleled that of IgG2a anticollagen antibodies, an isotype implicated in the pathogenesis of CIA by other laboratories. The collagen-specific IgE contained in the plasma of mice with CIA could arm basophils for Ag- (collagen) dependent degranulation. Collagen-specific IgE may thus contribute to CIA by promoting mast cell degranulation in the synovia of susceptible mice immunized with chick type II collagen; but, further work is required to establish such a role for IgE in CIA. However, genetic differences in disease susceptibility could not be accounted for by quantitative differences in collagen-specific IgE production. Further, comparable levels of IgE anticollagen antibodies were observed in animals with active CIA and after spontaneous remission, thereby confirming that the presence of such antibodies is insufficient for disease. Total IgE levels peaked just before spontaneous remission indicating active production of IL-4. IL-4 was administered to animals with CIA to determine if this lymphokine could be involved in the remission process. IL-4 facilitated remission of CIA. Enhanced total IgE production may thus be a marker for activation of Th2 cells that produce lymphokines such as IL-4 and IL-10, factors that may be involved in the spontaneous remission process.

Antiviral activity of 1-docosanol, an inhibitor of lipid-enveloped viruses including herpes simplex

This article reports that 1-docosanol, a 22-carbon-long saturated alcohol, exerts a substantial inhibitory effect on replication of certain viruses (e.g., herpes simplex virus and respiratory syncytial virus) within primary target cells in vitro. To study the basis for its viral inhibitory activity, a suspension of 1-docosanol was formulated in an inert and nontoxic surfactant, Pluronic F-68; this suspension exerted potent inhibitory activity on the ability of susceptible viruses to infect cultured target cells. Susceptible viruses included wild-type herpes simplex viruses 1 and 2 as well as acyclovir-resistant herpes simplex virus 2 and also respiratory syncytial virus--all of which are lipid-enveloped. In contrast, nonenveloped poliovirus was not susceptible to the inhibitory action of 1-docosanol. Although the precise mechanism has yet to be defined, current evidence suggests that 1-docosanol inhibits viral replication by interfering with the early intracellular events surrounding viral entry into target cells. It is possible that interaction between the highly lipophilic compound and components of target cell membranes renders such target cells less susceptible to viral fusion and/or entry. If this mechanism proves to be correct, 1-docosanol may provide a broad spectrum activity against many different viruses, especially those with lipid-containing envelopes.

The murine epsilon receptor modulating protein: a novel serine protease which modulates CD23 binding of IgE

In our recent previous studies, we have identified and purified a murine 17-kDa protein which diminishes the avidity of binding between IgE and CD23 (low-affinity Fc receptor for IgE) without decreasing the quantitative expression of the CD23. The protein was thus designated epsilon receptor modulating protein (epsilon RMP). In this study, we have further characterized this protein and have found that (i) epsilon RMP is inactivated by phenylmethylsulfonyl fluoride and decomposes N,alpha-benzyloxycarbonyl-L-lysine thiobenzyl ester, as well as N-succinyl-Ala-Ala-Pro-Phe p-nitroanilide; (ii) epsilon RMP does not work directly on B cells but requires CD4+ T cells to decrease functional expression of CD23 on B cells; and (iii) the partial internal amino acid sequence of epsilon RMP, obtained by using in situ cyanogen bromide cleavage on polyvinylidene difluoride membrane is unique. These data thus clearly demonstrate that epsilon RMP is a novel serine protease controlling the functional expression of CD23 through the participation of CD4+ T cells. Mechanisms of the involvement of CD4+ T cells are discussed.

Complete genomic sequence of the murine low affinity Fc receptor for IgE. Demonstration of alternative transcripts and conserved sequence elements

The complete sequence of the murine low affinity Fc receptor for IgE (Fc epsilon RII), including the 5' and 3' flanking sequences, is reported. The murine Fc epsilon RII gene spans 12.9 kb and includes 12 exons surrounding 11 introns. The composite exon sequence is virtually identical to previously reported murine Fc epsilon RII cDNA sequences. Much of the proximal promoter regions of the mouse and human homologues of Fc epsilon RII show remarkable homology to each other, including three promoter elements previously identified for MHC class II genes. The reported exon/intron structure of the human FC epsilon RII is similar to the murine homologue, except that the latter has an additional exon coding for a fourth amino acid repetitive sequence (vs three in the human gene). RNase protection studies have identified an additional transcript within intron 2 of murine Fc epsilon RIIa, similar to the human Fc epsilon RIIb form but with a different predicted sequence of the first six amino acids. This transcript is present in the mRNA of purified splenic B cells, but not in the mRNA of the Fc epsilon RII+ B lymphoma cell line M12.4.5. The murine Fc epsilon RII gene contains a large intron (4.2 kb) separating the lectin and nonlectin coding regions, and several repetitive sequences are found clustered within this intron. These results emphasize the importance of the demarcation between these domains and allude to their evolutionary and functional significance.

Complete genomic sequence of the murine low affinity Fc receptor for IgE. Demonstration of alternative transcripts and conserved sequence elements

The complete sequence of the murine low affinity Fc receptor for IgE (Fc epsilon RII), including the 5' and 3' flanking sequences, is reported. The murine Fc epsilon RII gene spans 12.9 kb and includes 12 exons surrounding 11 introns. The composite exon sequence is virtually identical to previously reported murine Fc epsilon RII cDNA sequences. Much of the proximal promoter regions of the mouse and human homologues of Fc epsilon RII show remarkable homology to each other, including three promoter elements previously identified for MHC class II genes. The reported exon/intron structure of the human FC epsilon RII is similar to the murine homologue, except that the latter has an additional exon coding for a fourth amino acid repetitive sequence (vs three in the human gene). RNase protection studies have identified an additional transcript within intron 2 of murine Fc epsilon RIIa, similar to the human Fc epsilon RIIb form but with a different predicted sequence of the first six amino acids. This transcript is present in the mRNA of purified splenic B cells, but not in the mRNA of the Fc epsilon RII+ B lymphoma cell line M12.4.5. The murine Fc epsilon RII gene contains a large intron (4.2 kb) separating the lectin and nonlectin coding regions, and several repetitive sequences are found clustered within this intron. These results emphasize the importance of the demarcation between these domains and allude to their evolutionary and functional significance.

Elicitation of antigen-induced primary and secondary murine IgE antibody responses in vitro

Described herein are methods for eliciting and quantitating primary and secondary murine IgE antibody responses in vitro, and the important role of antigen concentration in determining the level of IgE produced during an immune response. The methods for quantitating IgE antibody levels in culture supernatant fluids and in serum by ELISA are presented in detail. The specificity of such methods was confirmed in that (1) no other isotype of antibody registered in the IgE-ELISA, and (2) parallel determinations of IgE antibody concentrations could be obtained by independent analysis using Fc epsilon RI-dependent basophil degranulation. We examined various parameters of cell donor immunization and lymphoid cell culture which allow for optimal in vitro primary and secondary IgE responses. High relative antigen doses result in diminished IgE antibody responses in experimental animals, a finding confirmed herein. High antigen concentrations in vitro also result in relative suppression of IgE antibody synthesis. This was also true for in vitro production of IgG1 and IgA antibodies. Conversely, IgM and IgG2a responses were elicited at both low and high antigen concentrations; IgG2b and IgG3 were not produced under the conditions of priming and culture used herein. Finally, production of IgE in vitro depended on the presence of carrier-primed CD4+ T cells and hapten-specific B cells. Generation of maximal IgE antibody secretion, and hence elicitation of an allergic reaction, is thus dependent on the amount of antigen acting as stimulant for the immune response.

Purification of murine suppressive factor of allergy into distinct CD23-modulating and IgE-suppressive proteins

The murine suppressive factor of allergy (SFA) has been purified from a T-cell hybridoma and found to consist of two functionally and biochemically distinct protein molecules. One protein (17 kDa) modulates the low-affinity Fc receptor for IgE on lymphocytes (i.e., CD23); it decreases the binding avidity of IgE to CD23-bearing B cells without affecting quantitative expression of CD23 and is thus designated epsilon-receptor-modulating protein. The second protein (30 kDa) suppresses IgE biosynthesis (i.e., SFA). This purified SFA suppresses interleukin 4-induced IgE and IgG1 synthesis by lipopolysaccharide-activated spleen cells but has no effect on other antibody isotypes; since the activity of SFA is not blocked by anti-interferon gamma monoclonal antibody, it is thus distinct from interferon gamma. The data presented indicate that epsilon-receptor-modulating protein and SFA are protein molecules that are involved in modulating the CD23 molecule and IgE antibody synthesis, respectively.

Human rib bone marrow mononuclear cells spontaneously synthesize and secrete IgE in vitro

We have examined spontaneous secretion of IgE by human rib bone marrow mononuclear cells (MNC). Bone marrow MNC from nine out of 12 rib specimens synthesized and secreted substantial amounts of IgE during 14 days of in vitro culture. The 14-day supernatants from these bone marrow MNC contained a mean of 2589 pg/ml of IgE (n = 12) with a maximum production of 15,408 pg/ml of IgE compared with small amounts of IgE (80-200 pg/ml) produced by similarly cultured normal and inflammatory bowel disease intestinal lamina propria MNC. Using two rib specimens, time-course studies revealed spontaneous secretion of IgE to be minimal during the first 2 days of culture (152 pg/ml), followed by a steady increase between days 4 (517 pg/ml) and 14 (3588 pg/ml). The addition of pokeweed mitogen resulted in 72% suppression of spontaneous IgE production by bone marrow MNC. The bone marrow MNC isolated from the ribs consisted of 22% Leu12+ (B) cells of which 3.2% were surface IgE positive. Staining for cytoplasmic immunoglobulin revealed 1% of the bone marrow MNC to be cytoplasmic IgE+. The presence of IgE-bearing and IgE-secreting MNC in human bone marrow is consistent with the observation that allergen-specific IgE-mediated hypersensitivity is adoptively transferred by human bone marrow transplantation and demonstrates the usefulness of human bone marrow MNC for examination of IgE secretory and regulatory events.

The induction of murine B cell Ia by IgE-antigen complexes is dependent on protein synthesis and preceded by class II mRNA accumulation

Complexes of murine monoclonal anti-DNP IgE and DNP-OVA interact with murine B cells to stimulate expression of cell surface Ia antigens. Enhanced membrane expression of class II MHC antigens was accompanied by a threefold increase of I-A and I-E transcripts, as measured by Northern blot. Peak accumulation of Ia mRNA were detected after 6 hr of incubation with IgE-antigen complexes and returned to control levels after 12 hr of incubation. Hence, induction of Ia mRNA by IgE-antigen complexes was compatible with cell surface Ia expression, both quantitatively and with regard to the time frame. The Ia-inductive effects of both IL-4 and IgE-antigen complexes were inhibited by cycloheximide and actinomycin-D. However, whereas actinomycin-D and cycloheximide blocked IL-4 induction of Fc epsilon RII expression, inhibition of transcription or protein synthesis did not abrogate the increased expression of Fc epsilon R associated with IgE-antigen complexes. These results suggest that the IgE-antigen-induction of B cell Ia expression follows from activation of transcription and de novo synthesis of Ia antigens.

Comparison of laboratory test use among three urgent care clinics

Laboratory test ordering practices among physicians at three walk-in or urgent-care medical facilities were compared to evaluate the relationship between practice type and test ordering patterns. The charts of 221 patients were reviewed for test ordering as an aid for the diagnosis of cough or upper respiratory infection (169 patients) or diarrhea (52 patients). For upper respiratory infections, the free-standing walk-in clinic ordered the greatest number of tests; and for both categories of disease, the urgent care unit of a health maintenance organization (HMO) ordered the fewest tests.

The binding of IgE to murine Fc epsilon RII is calcium-dependent but not inhibited by carbohydrate

Despite extensive study, little is known about the functions of the moderate affinity IgE receptors (Fc epsilon RII) on B cells. Recent cDNA and genomic cloning studies have demonstrated that, in contrast to other FcR, Fc epsilon RII is not a member of the Ig gene superfamily. Moreover, it uniquely expresses a region that is highly homologous with a membrane-associated, calcium-dependent binding lectin, the asialoglycoprotein receptor. We now report that the interaction between IgE and the Fc epsilon RII of murine B cells and macrophages requires calcium. Furthermore, as might be expected of asialoglycoprotein lectins, this binding was pH-dependent and resulted in ligand internalization. However, although 125I-Fc epsilon RII bound in a calcium-dependent manner to monosaccharide-agarose beads, high concentrations of mono- and disaccharides did not inhibit the interaction between either 125I-IgE and intact B cells or 125I-Fc epsilon RII (from surface-labeled B cells) and IgE-Sepharose. These results suggest that although murine Fc epsilon RII is a lectin, it is not strictly dependent upon IgE oligosaccharides for its binding to IgE.

The binding of IgE to murine Fc epsilon RII is calcium-dependent but not inhibited by carbohydrate

Despite extensive study, little is known about the functions of the moderate affinity IgE receptors (Fc epsilon RII) on B cells. Recent cDNA and genomic cloning studies have demonstrated that, in contrast to other FcR, Fc epsilon RII is not a member of the Ig gene superfamily. Moreover, it uniquely expresses a region that is highly homologous with a membrane-associated, calcium-dependent binding lectin, the asialoglycoprotein receptor. We now report that the interaction between IgE and the Fc epsilon RII of murine B cells and macrophages requires calcium. Furthermore, as might be expected of asialoglycoprotein lectins, this binding was pH-dependent and resulted in ligand internalization. However, although 125I-Fc epsilon RII bound in a calcium-dependent manner to monosaccharide-agarose beads, high concentrations of mono- and disaccharides did not inhibit the interaction between either 125I-IgE and intact B cells or 125I-Fc epsilon RII (from surface-labeled B cells) and IgE-Sepharose. These results suggest that although murine Fc epsilon RII is a lectin, it is not strictly dependent upon IgE oligosaccharides for its binding to IgE.

Fc receptors for IgE (Fc epsilon R) on human lymphoid cells: inducible expression of Fc epsilon RII (CD23) on lymphocytes and detection by monoclonal anti-Fc epsilon RII antibody

The studies presented herein describe (1) a sensitive, quantitative, and objective assay for detecting cell membrane-bound form of Fc receptors for IgE displayed on human lymphoid cells based on measuring unlabeled Fc epsilon R-bound IgE by a solid-phase RIA of cell lysate fluids; (2) the development and characterization of an IgM monoclonal antibody, termed 7E4, which is specific for human lymphocyte Fc epsilon RII (CD23) molecules; and (3) a system for reproducibly inducing de novo synthesis and expression of Fc epsilon RII proteins on human lymphocytes following exposure to the mitogenic lectin, pokeweed mitogen. The Fc epsilon RII molecules induced by exposure to PWM were proven to be present on lymphocytes, and not on other cell types in several ways, including (1) documenting sensitivity of such proteins to both acid pH and trypsin treatment, the latter manipulation being ineffective in removing Fc epsilon RII molecules on basophils and mast cells; (2) demonstrating specific reactivity of the expressed Fc epsilon RII molecules with the 7E4 monoclonal antibody, which is specific for human lymphocyte Fc epsilon RII molecules and does not react with Fc epsilon R molecules on other cell types; and (3) observing the required concomitant presence of both T and B lymphocytes during the induction process and proving that the induced Fc epsilon R+ cells are indeed B cells of the Leu-12+ phenotype by fluorescence analysis. The ability to induce expression of Fc epsilon RII molecules on human lymphocytes exposed to a mitogen such as PWM requires special technical attention to the method of preparation and isolation of human lymphoid cells from peripheral blood. This in vitro system for up-regulating Fc epsilon RII expression on human lymphocytes should provide us with an important new tool to analyze the participation of such cells in the regulatory mechanisms controlling the human IgE antibody system.

The cellular lesion responsible for exaggerated IgE synthesis accompanying allergic breakthrough

Appropriate levels of IgE are maintained by a cellular and molecular network composed of (1) a suppressive, Ly-1+, CD4+ T cell-dependent arm that is activated by inappropriate high levels of IgE and (2) an enhancing, CD8+ T cell-dependent arm that controls this suppression in a feedback regulatory manner. Ly-1+ T cells also function to counterbalance (inhibit) the activity of these latter CD8+ T cells. It has been previously shown that Ly-1+ T cells can reverse low-dose irradiation-induced enhancement of IgE antibody responses (i.e., allergic breakthrough). We have analyzed lymphocytes isolated from mice subjected to low-dose irradiation to determine which component of this network is defective in such animals. Stimulation of normal lymphocytes with IgE in vitro resulted in the release of lymphokines that suppress IgE antibody responses. In contrast, similar stimulation of lymphocytes from irradiated mice did not elicit secretion of such suppressive lymphokines, unless the cells were depleted of CD8+ T cells or reconstituted with normal Ly-1+ T cells. Because Ly-1+ T cells of irradiated mice could not reconstitute the response, we conclude that this functional subset of CD4+ T cells, which normally controls CD8+ T cell activity in this network, is defective in animals that exhibit irradiation-induced allergic breakthrough.

Cloning of cDNA coding for low-affinity Fc receptors for IgE on human T lymphocytes

Using a cDNA probe corresponding to the membrane-bound form of the B cell receptor for IgE, we have isolated, sequenced, and expressed a cDNA clone which codes for a human T lymphocyte Fc epsilon R from HUT-78 cells. This T cell Fc epsilon R cDNA codes for 320 amino acid residues, and shows high homology to the B cell Fc epsilon R sequence. The major differences between this T cell and the B cell Fc epsilon R cDNA sequences are (i) a limited stretch of nucleotides at the 5' segment of the coding region which encodes a putative cytoplasmic region of the Fc epsilon R molecule and the untranslated 5' end; and (ii) an additional 64 bp segment in the untranslated 3' end containing two repeats in tandem with three existing repeats in the same region. The expression of Fc epsilon R on T lymphocytes may reflect involvement of the Fc epsilon R in regulation of IgE-mediated responses. The cytoplasmic difference implies functional activity of the Fc epsilon R in T lymphocytes that is mechanistically different from the Fc epsilon R of B lymphocytes.

IgE-antigen complexes enhance Fc epsilon R and Ia expression by murine B lymphocytes

Murine monoclonal IgE interacts with B cells of BALB/c mouse spleen with greater efficiency in the presence of its specific antigen. Complexes of anti-DNP IgE and DNP-OVA not only resist elution from B lymphocytes by acid but have a substantially longer dissociation half-time when compared with monomeric IgE (440 vs. 8 min, respectively). Further, these IgE-antigen complexes induce Fc epsilon R expression in lymphoid cells more efficiently than IgE alone. Maximum levels of B cell Fc epsilon R were observed after a 24 h incubation with 1 microgram/ml IgE in the presence of 1 microgram/ml DNP-OVA, while 30 micrograms/ml monomeric IgE was needed to elicit a similar increase of Fc epsilon R expression. Most importantly, overnight incubation of B cell-enriched BALB/c spleen cells with IgE-antigen complexes resulted in an augmented membrane expression of class II MHC antigens. B cell surface expression of both I-A and I-E antigens responded to a comparable level after incubation with IgE-antigen complexes but did not occur in response to either IgE or antigen alone. The enhanced sIa expression occurred in parallel to IgE-antigen concentrations that gave rise to Fc epsilon R hyperexpression. Moreover, double staining for Fc epsilon R and surface Ia antigen shows that B cells exhibiting the highest density of Fc epsilon R also demonstrated the most surface I-A, suggesting that B lymphocytes are autonomous in their response to IgE-antigen complexes. Changes in class I MHC or sIgM were not observed after overnight incubation with IgE and antigen. These results demonstrate the importance of IgE-antigen complexes for intercellular signaling and further suggest that the IgE system plays a broader role in immune response than it has generally been credited.

Production of IL-1-mimicking anti-idiotypic antibodies in rabbits in response to IL-1 immunization

This report describes the characterization of immunoglobulins with interleukin-1 (IL-1)-like activity from the serum of rabbits immunized with partially purified mouse IL-1. Early after immunization, immune sera were found to contain anti-IL-1 antibodies (idiotypes) that inhibited IL-1 bioactivity (augmented-proliferation of PHA-stimulated thymocytes). Later, anti-idiotypic antibodies appeared that mimicked IL-1 activity. These IL-1-like antibodies were affinity purified either on an anti-IL-1-enriched Ig-Sepharose 4B column from an early bleed or sequentially on anti-Ig and Protein A immunoadsorbent columns. By ELISA anti-idiotypic antibodies specifically bound to rabbit anti-IL-1 antibodies. Functionally, IL-1 mimicking antibodies were reproducibly effective in augmenting the in vitro proliferation of PHA-stimulated thymocytes or Con A-stimulated D10 cells. On the other hand, they did not support proliferation of the IL-2-dependent CTLL-2 cells. The ability of IL-1-mimicking antibodies to enhance thymocyte proliferation could be blocked by functional site related anti-IL-1 antibodies. By Western blot, 125I-labeled IL-1 and IL-1-mimicking antibodies bound to a similar 23 Kd mol. wt protein material recovered from the lysate of thymocytes stimulated with PHA for 48 h. That the observed bioactivity could be attributed to antibody molecules and not to contaminant IL-1 was ascertained by several methods, namely (1) SDS-PAGE analysis of 125I-labeled material and (2) resistance to loss of bioactivity by lyophilization. Furthermore, as neither Ig-anti-Ig nor BSA-anti-BSA complexes mimicked IL-1-augmented thymocyte proliferation, a non-specific effect due to immune complexes could be excluded. The occurrence of antibodies mimicking several of the IL-1 functions induced following IL-1 immunization suggests a potential role for the idiotypic network in modulating cytokine activities and a possible link between regulation of the immune system by cytokines and immunoglobulin idiotypes.

Perturbation of the autoimmune network. I. Immunization with anti-idiotypic antibodies prior to challenge with antigen induces quantitative variations in the autoantibody response

The effect of immunization with anti-idiotypes on the production of autoantibodies subsequently induced with nominal antigen, thyroglobulin, was investigated in BALB/c mice with three distinct rabbit antibodies and one syngeneic monoclonal antibody (mAb) specific for an idiotype (Id62) borne on a mouse monoclonal autoantibody to thyroglobulin. In these in vivo experiments, dose, route and form of the anti-idiotypic immunization were kept constant, but the time interval between exposure to anti-idiotype and antigen challenge was varied. When the interval was short (two weeks), heterologous anti-Id62 antibodies predisposed to suppression of the autoantibody response in 2/3 instances. Suppression was also obtained in mice immunized with a syngeneic mAb directed against Id62. In each case, a prominent idiotype-positive (Id') response was measured in the serum. Adsorption/elution studies indicated that Id' molecules in suppressed mice were principally non antigen-binding. On the other hand, when the time interval between injections was long (14 weeks), mice preimmunized with one rabbit anti-Id62 antibody showed a markedly increased autoantibody response. The Id' component in enhanced mice was largely enriched for antibodies reacting with the antigen. These findings suggest that the state of activation of autoreactive clones and the type of anti-idiotypes used may be determinant factors in the overall effect of manipulation of autoimmune responses with anti-idiotypic antibodies.

Characterization of murine interleukin B by a monoclonal antibody

Interleukin B (IL-B), formerly termed BEF (B-cell-derived enhancing factor) or IL-B4, was originally described as a non-immunoglobulin regulatory factor spontaneously produced by B lymphocytes and B-cell lines that enhances the in vitro antigen-driven antibody response of unfractionated spleen cells stimulated by thymus-dependent antigens. Since then we have examined the function of interleukin B in a number of immune reactions, both in vitro and in vivo, and found that it inhibits the activation of suppressor T lymphocytes. We report here the production of two monoclonal antibodies (mAb) that specifically inhibit interleukin B activity. The use of these mAb in the purification and characterization of IL-B is described. IL-B from both normal and transformed B cells consists of two subunits of similar size and amino-acid composition. The structure of interleukin B and its specific behaviour in biological assay distinguish it from many other known lymphokines.

Inhibitory activity of interleukin B on the suppressor T cell hybrid T2D4

Interleukin B (IL-B), a product of unstimulated B cells, is defined by its ability to selectively prevent the differentiation of suppressor T lymphocytes from precursors into effectors. The present study was undertaken to determine whether IL-B could also be active in modulating the activity of the T cell hybrid T2D4, which produces immunoglobulin-binding suppressor factors. T2D4 cells can be selectively induced by incubation with various isotypes of antibody to express isotype-specific Fc receptors and to release soluble factors that suppress production of the corresponding isotype. The data presented here demonstrate that IL-B is greatly effective in inhibiting T2D4 activities. Either pretreatment with IL-B or continuous exposure to IL-B prevents isotype activation of T2D4. As a result, T2D4 cells do not express isotype receptors and do not produce detectable amounts of isotype-specific suppressor factors. This IL-B regulatory activity on T2D4 is temperature dependent and is inhibited by cytochalasin B. These findings provide new insights on the mechanism by which IL-B enhances antibody responses, and they offer a conceptual framework for analyzing IL-B activity on suppressor T cells.

Inhibitory activity of interleukin B on the suppressor T cell hybrid T2D4

Interleukin B (IL-B), a product of unstimulated B cells, is defined by its ability to selectively prevent the differentiation of suppressor T lymphocytes from precursors into effectors. The present study was undertaken to determine whether IL-B could also be active in modulating the activity of the T cell hybrid T2D4, which produces immunoglobulin-binding suppressor factors. T2D4 cells can be selectively induced by incubation with various isotypes of antibody to express isotype-specific Fc receptors and to release soluble factors that suppress production of the corresponding isotype. The data presented here demonstrate that IL-B is greatly effective in inhibiting T2D4 activities. Either pretreatment with IL-B or continuous exposure to IL-B prevents isotype activation of T2D4. As a result, T2D4 cells do not express isotype receptors and do not produce detectable amounts of isotype-specific suppressor factors. This IL-B regulatory activity on T2D4 is temperature dependent and is inhibited by cytochalasin B. These findings provide new insights on the mechanism by which IL-B enhances antibody responses, and they offer a conceptual framework for analyzing IL-B activity on suppressor T cells.

FcR epsilon+ lymphocytes and regulation of the IgE antibody system. V. Preliminary physicochemical characterization of the T cell-selective IgE-induced regulant EIRT

We previously showed that murine lymphoid cells exposed to elevated levels of IgE exhibit the de novo expression of Fc receptors for IgE (FcR epsilon), and the production of soluble mediators, which we have termed IgE-induced regulants (EIR). Described herein is the preliminary physicochemical characterization of one such regulant, that being the EIR responsible for the Lyt-2+ T cell-dependent expression of FcR epsilon and secretion of an IgE-binding factor (IgE-BF) which can potentiate IgE synthesis; the former activity has been denoted EIRT for its selectivity of action on T cells, and the latter activity has been termed enhancing effector molecule (EEM) for its presumed potentiating influence on IgE antibody synthesis. Characterized in parallel was the conventional lymphoid cell-derived cEIRT and a murine monoclonal T cell hybridoma-(MBI-2)-derived mcEIRT. EIRT from either source was shown to exhibit the characteristics of a protein with a molecular mass of 45 to 60 kd. Once enriched by gel filtration, neither cEIRT nor mcEIRT preparations displayed any other EIR-like activity except that of EIRT, as evidenced by the ability of these preparations to act selectively to induce the Lyt-2 T cell-dependent expression of FcR epsilon and the production of EEM, the lack of detectable SFA activity that could induce Lyt-1+ T cells to produce the IgE-BF denoted suppressive effector molecule (SEM), and the lack of detectable levels of the B cell-selective EIRB, as indicated by the incapacity of either preparation to induce B cell FcR epsilon expression. Neither cEIRT nor mcEIRT displayed IgE-binding affinity, in contrast to the EEM produced in response to stimulation with these regulants. The only EIR-like activity detected in the unfractionated supernatant fluid from cultures of the monoclonal T cell hybridoma MBI-2 was that of EIRT. Careful in vitro analysis established that such preparations did not contain enhancing factor of allergy (EFA), SFA, EIRB, or IgE-BF. Thus, the enhancement of IgE synthesis observed in animals given this mcEIRT preparation was most likely due to the activity of EIRT known to be present. During the course of these studies, clues as to the physicochemical nature of other EIR activities was obtained. Thus, upon molecular sieve analysis, two distinct molecular mass species of EIRB (one 15 to 20 kd and the other 30 to 35 kd) were demonstrated to be present in conventional lymphocyte-derived cEIR.(ABSTRACT TRUNCATED AT 400 WORDS)

FcR epsilon+ lymphocytes and regulation of the IgE antibody system. V. Preliminary physicochemical characterization of the T cell-selective IgE-induced regulant EIRT

We previously showed that murine lymphoid cells exposed to elevated levels of IgE exhibit the de novo expression of Fc receptors for IgE (FcR epsilon), and the production of soluble mediators, which we have termed IgE-induced regulants (EIR). Described herein is the preliminary physicochemical characterization of one such regulant, that being the EIR responsible for the Lyt-2+ T cell-dependent expression of FcR epsilon and secretion of an IgE-binding factor (IgE-BF) which can potentiate IgE synthesis; the former activity has been denoted EIRT for its selectivity of action on T cells, and the latter activity has been termed enhancing effector molecule (EEM) for its presumed potentiating influence on IgE antibody synthesis. Characterized in parallel was the conventional lymphoid cell-derived cEIRT and a murine monoclonal T cell hybridoma-(MBI-2)-derived mcEIRT. EIRT from either source was shown to exhibit the characteristics of a protein with a molecular mass of 45 to 60 kd. Once enriched by gel filtration, neither cEIRT nor mcEIRT preparations displayed any other EIR-like activity except that of EIRT, as evidenced by the ability of these preparations to act selectively to induce the Lyt-2 T cell-dependent expression of FcR epsilon and the production of EEM, the lack of detectable SFA activity that could induce Lyt-1+ T cells to produce the IgE-BF denoted suppressive effector molecule (SEM), and the lack of detectable levels of the B cell-selective EIRB, as indicated by the incapacity of either preparation to induce B cell FcR epsilon expression. Neither cEIRT nor mcEIRT displayed IgE-binding affinity, in contrast to the EEM produced in response to stimulation with these regulants. The only EIR-like activity detected in the unfractionated supernatant fluid from cultures of the monoclonal T cell hybridoma MBI-2 was that of EIRT. Careful in vitro analysis established that such preparations did not contain enhancing factor of allergy (EFA), SFA, EIRB, or IgE-BF. Thus, the enhancement of IgE synthesis observed in animals given this mcEIRT preparation was most likely due to the activity of EIRT known to be present. During the course of these studies, clues as to the physicochemical nature of other EIR activities was obtained. Thus, upon molecular sieve analysis, two distinct molecular mass species of EIRB (one 15 to 20 kd and the other 30 to 35 kd) were demonstrated to be present in conventional lymphocyte-derived cEIR.(ABSTRACT TRUNCATED AT 400 WORDS)

B-lymphocyte regulation of the immune system. III. Preparation and characterization of rabbit antibodies that inhibit the biological activity of the lymphokine, B-cell-derived enhancing factor (BEF)

Antibodies that inhibit the biological activity of B-cell-derived enhancing factor (BEF) were produced in a rabbit immunized with BEF obtained from a non-immunoglobulin-producing B-cell line. Immunoglobulin G (IgG) fractions purified from the preimmune or the immune rabbit serum were compared by testing for their capacity to inhibit regulatory activities of BEF. It was found that the enhancing activity exerted by BEF on the in vitro antibody response to sheep red blood cells was inhibited when anti-BEF IgG was incorporated in the cultures. Moreover, anti-BEF IgG abolished the inhibitory activity exerted by BEF on the expression of Fc receptor by lymphoid cells. Comparable concentrations of preimmune IgG were ineffective in inhibiting BEF activity. The passage of supernatant fluid containing BEF activity through an anti-BEF IgG-coupled Sepharose column yielded an 84-fold purified product that exhibit BEF immunoregulatory properties. These results will accelerate further studies aimed at better characterization of the BEF molecule(s).

Use of a portable ribosome-binding site for maximizing expression of a eukaryotic gene in Escherichia coli

To maximize expression of a eukaryotic gene in Escherichia coli, a series of plasmids were constructed containing various synthetic ribosome-binding sites (RBS). These sites consist of a Shine-Dalgarno (SD) region (with translation stop codons in all three reading frames) positioned at distances 5-9 nucleotides (nt) from the AUG initiator codon of the gene coding for human T-cell growth factor (TCGF or IL-2). The region encompassing the RBS through the TCGF structural gene from each of these plasmids was inserted as a 'cassette' into seven different E. coli expression vectors, and TCGF production was measured. Our results demonstrate a greater than 2000-fold range of TCGF synthesis dependent upon the promoter and the synthetic RBS used. The translational efficiency of the TCGF gene was found to be influenced by the quality of the RBS, which is in part determined by the external sequence context of this site. The synthetic RBS, containing the necessary information for the translation initiation process, readily accessible by restriction sites, should be of general usefulness in obtaining maximum expression of eukaryotic genes in E. coli.