Regulation of IgE antibody production by serum molecules. VI: Preliminary biochemical and immunological characterization of serum molecules active in suppressing IgE antibody production

The polyclonal and antigen-specific IgE and IgG subclass response of mice injected with ovalbumin in alum or complete Freund's adjuvant

BALB/c mice were injected ip with 1 microgram ovalbumin (OVA) in alum or complete Freund's adjuvant (cFA) and the changes of the IgE and IgG subclass serum levels and isotypes of the anti-OVA specific antibodies determined by radioimmunoassays. By Day 10, OVA in alum had induced a 5- to 10-fold increase of the IgE serum level and an initial decrease of the IgG subclass levels which subsequently increased to two to threefold over the preinjection level. OVA in cFA induced a gradual twofold increase of the IgE serum level, a rapid fourfold increase of the IgG2a level occurring by Day 7, and a gradual two to threefold increase of the other IgG subclasses. Over 90% of the anti-OVA antibodies were of the IgGl isotype with both adjuvants; OVA in alum induced slightly more IgGl anti-OVA antibodies than cFA. In contrast, the OVA in alum injected mice formed significantly more (5- to 10-fold) IgE anti-OVA antibodies than the cFA-injected mice. OVA in alum also induced a large nonspecific increase of the IgE serum level because only approximately 40% of the increase observed on Day 14 was absorbable with OVA, whereas approximately 90% the IgE increase in cFA injected mice was absorbable with OVA. The data demonstrate that mice form mainly IgGl and IgE antibodies to OVA irrespective of the adjuvant. The low specific and lack of nonspecific IgE formation by mice injected with OVA in cFA may be the result of cFA-induced interferon-gamma (IFN-gamma) production because IFN-gamma has been shown to stimulate IgG2a and inhibit IgE secretion in vitro.

IgE synthesis in vitro during infection of mice with the nematode Nippostrongylus brasiliensis: effects of mitogens and antigens

In vitro IgE synthesis by lymphoid cells was studied during the course of infection of mice with Nippostrongylus brasiliensis. The studies involved inbred strains of mice which had been shown to be high IgE responders (A.CA, B10.M), or non-responders (Balb/c, B10.D2) to parasite antigen. In addition, F1 hybrids of low and high responders and irradiated non-responders were studied. Infection with N. brasiliensis led to an increase in IgE synthesis in vitro which was most pronounced during reinfection of mice. Addition of mitogens e.g. pokeweed mitogen (PWM), lipopolysaccharide (LPS), concanavalin A (ConA) to the cultures induced enhancement, suppression or had no effect on IgE synthesis. Addition of N. brasiliensis homogenate or worm culture supernatant led to a fluctuating pattern of IgE synthesis. No correlation was found between lymphocyte proliferative response to mitogen and worm antigens and IgE synthesis. Our data suggest, that PWM is more likely to enhance IgE synthesis in vitro than LPS or ConA. An enhancement is more easily observed with the cells of non-infected animals or during the early phase of infection or reinfection. The mitogen-induced increase in IgE synthesis did not exceed the values obtained during infection or reinfection.

IgE-specific suppressor factors in normal human serum

The effect of normal human serum on in vitro IgE production was studied in an attempt to determine whether IgE-specific suppressor factors are present in the circulation of nonallergic individuals. Sera from 10 nonatopic donors (serum IgE less than 20 I.U./ml) were filtered through Diaflo CF50A membranes (cutoff point 50,000 D) and various dilutions of the IgE-free serum filtrates (less than 150 pg/ml of IgE) were examined for their ability to suppress spontaneous in vitro IgE synthesis by peripheral blood mononuclear cells (PBMC) from patients with hyper-IgE states. Serum filtrates from all 10 nonatopic donors tested suppressed IgE synthesis (mean suppression = 70 +/- 4%). IgE suppression was isotype specific because addition of the serum filtrates to pokeweed mitogen-stimulated normal PBMC or to spontaneously activated B cells from patients with active systemic lupus erythematosus did not suppress IgG or IgM production. The IgE suppressor activity was destroyed by treatment with trypsin but not with neuraminidase or exposure to heat. Substantial suppressor activity bound to IgE-Sepharose but not to a control IgG-Sepharose column. Further evaluation of the IgE-binding serum IgE suppressor factor(s) revealed a marked affinity for peanut agglutinin-Sepharose but minimal binding to lentil lectin-Sepharose. These results suggest that human serum from nonatopic donors contain low molecular weight IgE-binding factors which selectively suppress IgE production but not IgG production. Characterization of ths IgE-binding suppressor factor(s) reveals physicochemical features similar to those previously described for rat T-cell-derived IgE-binding factors with IgE suppressive activity.

A clonal analysis of the IgE response and its implications with regard to isotope commitment

In a clonal analysis of the IgE response, it was found that a small proportion of primary or nonimmune B cells in spleen and mesenteric lymph nodes can be stimulated by antigen to produce IgE-secreting clones. In addition, there appears to be no substantial difference in the frequency of such cells between the classical low and high IgE responder strains. An analysis of immune, or memory, B cells revealed substantial increases in the frequency of B cells secreting IgE as compared with primary B cells, although the actual proportion of B cells secreting IgE remained relatively low. When the IgE-secreting clones derived from either primary or secondary B cells were reanalyzed for the presence of other isotypes, it was found that all clones secreting IgE were secreting at least one other isotype, with the majority secreting two or three other isotypes in addition to IgE. This demonstrates that there is no distinct subpopulation of B cells committed to IgE expression per se.

New concepts concerning the clinical control of IgE synthesis

Prospects for new therapeutic approaches to IgE-mediated allergic diseases have arisen from (1) recent experimental observations that have suggested new concepts concerning the pathogenesis of the allergic phenotype, and (2) adaptation of previously described methods for induction of specific immunological tolerance to problems to allergy. The bases for these new approaches to allergic diseases are summarized herein.