Hans L. Spiegelberg

Biological activities of immunoglobulins of different classes and subclasses.

Publisher Summary This chapter discusses the biological activities of immunoglobulins of different classes and subclasses. This chapter illustrates that all immunoglobulins are composed of two types of polypeptide chains, heavy and light, which are linked by disulfide bonds. The biological activities of immunoglobulins may be divided into two categories: (1) the specific reaction with antigen and (2) the consequences of antigen - antibody reactions. The reaction with antigen has been called the primary function of immunoglobulins and is a property of the Fab fragment. This chapter reviews the biological activities that follow antigen-antibody reactions and that have been called the secondary functions of immunoglobulins. It has now been shown that the antibodies of the various classes and subclasses differ in their biological activities, and, in the future, one should attempt to determine how frequently restricted immune responses occur and how important such restricted antibody formation is in immune deficiency syndromes.

Structure and function of Fc receptors for IgE on lymphocytes, monocytes, and macrophages.

Publisher Summary This chapter establishes that the Fc fragment of immunoglobulins E (IgE) binds with high affinity to specific cell surface receptors (FcɛR) on basophils and mast cells and that cross-linking of FcɛR by antigen–IgE antibody complexes, aggregated IgE or anti-IgE receptor antibodies induces histamine release from these cells. Immunologists were somewhat surprised when it was found that radiolabeled aggregated IgE binds to human lymphocytes and an IgE-dependent killing of schistosomules by rat macrophages (MФ) was described, two observations that suggested the presence of FcɛR on lymphocytes and MФ. Several other researches on the interaction of IgE with lymphocytes and MФ established that these cells carry specific IgE Fc receptors, albeit of a different nature than those on basophils and mast cells. By employing methods involving multiple IgE–FcɛR interactions, such as rosette formation with IgE-coated erythrocytes, cells expressing low-affinity FcɛR can be detected relatively easily. The binding properties of radiolabeled IgE to FcɛR+ human cultured lymphoblastoid cells mouse lymphocytes, cultured human U937 MФ and The binding properties of radiolabeled IgE to FcɛR+ human cultured lymphoblastoid cells, mouse lymphocytes , cultured human U937 MФ have been reported.

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 Freunds 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.

Lymphocytes bearing Fc receptors for IgE.

In 1960, Boyden & Sorkin showed that certain rabbit antibodies bind to macrophages, and they designated them cytophilic antibodies. Subsequently, Berken & Benacerraf (1966) demonstrated that IgG binds to macrophages via the Fc fragment. Antibodies cytophilic to lymphocytes were first described by LoBuglio et a!. (1967), but this phenomenon was not investigated further until 1972, when several laboratories reported the binding of IgG to B and T cells. Paraskevas et al. (1972) showed that B cells bind IgG and they coined the term Fc receptor for the membrane structure binding IgG. Basten et al. (1972) investigated the binding of several Ig classes to murine B lymphocytes and found that IgGl binds better than IgG2a, IgM and IgA. Dickier & Kunkel (1972) showed that most human B cells bind aggregated IgG. Grey et al. (1972) and Yoshida & Anderson (1972) made the first observations of IgG binding to T cells. In recent years, the cytophilic binding of Ig of different classes has been extensively analyzed and Fc receptors to all five major Ig classes have been detected on subpopulations of lymphocytes. The majority (40-70%) of T cells have Fc receptors for IgM (Moretta etal. 1975). Smaller fractions (5-15%) of T cells have Fc receptors for IgG (Moretta et al. 1975), IgA (Lum et al. 1979a), IgE (Yodoi & Ishizaka 1979a) and IgD (Sjoberg 1980). Most B cells have Fc receptors for IgG (Dickler 1976), while subpopulations have Fc receptors for IgM (Ferrarini et al. 1977), IgA (Lum et al. 1979b) IgE (Gonzalez-Molina & Spiegelberg 1977) and IgD (Sjoberg 1980). Lymphocytes binding IgF were first detected in our laboratory (Lawrence et al. 1975, Gonzalez-Molina & Spiegelberg 1976, Gonzalez-Molina and Spiegelberg 1977), and our findings on the ¥cr lymphocyte population are reviewed in this chapter.

Biological role of different antibody classes

Antibodies are divided into different classes and subclasses (isotypes) according to structural differences in the constant region of the heavy polypeptide chains. The different isotypes mediate specific biologic functions that are important for the response to pathogens and in the pathogenesis of immunological diseases such as allergies. The numbers of different isotypes vary in different species, humans have 9 different Ig classes and subclasses. Of these 9, only IgM, IgG1, IgG2 and IgG3 activate the classical pathway of complement. All four IgG and both IgA subclasses, but not IgM, IgE and IgD, bind to Fc receptors on neutrophils, and induce the release of granule enzymes. All four IgG subclasses but no other Ig isotype induce serotonin release from platelets. In man, only IgE binds to the high-affinity Fc receptors (Fc epsilon RI) on mast cells and basophils and induces histamine and leukotriene release. IgE also binds to low-affinity Fc receptors (Fc epsilon RII) on lymphocytes, monocytes and eosinophils; however, the functions of Fc epsilon RII on these cells are not fully established. Monocytes from patients with atopic dermatitis that express more Fc epsilon RII than monocytes from normals do not release more LTC4 than monocytes from nonallergic healthy humans after activation with aggregated IgE. IgG and IgA are more efficient than IgE in inducing the release of mediators of inflammation from monocytes. The antibody response to certain antigens such as carbohydrates and allergens are often restricted to IgG2 and IgG1, IgG4 and IgE, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Fc receptors specific for IgE on subpopulations of human lymphocytes and monocytes

Abstract Fc receptors for IgE (Fcϵ) were detected on human lymphocytes and monocytes by rosette assays employing ox (E0) or chicken (Ec) erythrocytes coated with human myeloma IgE. Peripheral blood from normal donors contained 1.2 ± 0.6% Fc ϵ + lymphocytes and 23 ± 8% Fc ϵ + monocytes. Over 90% of the Fc ϵ + lymphocytes were B cells that did not have Fc receptors for IgG (Fcγ). Patients with severe atopic disease and highly elevated IgE levels had significantly higher percentages (7.0 ± 2.0%) of Fc ϵ + lymphocytes. Cells from 18 of 28 established human B lymphoblastoid cell lines were Fc ϵ + ; 16 of these were Fc γ − and only two were Fc ϵ + and Fc γ + . The affinity of monomeric IgE for Fcϵ receptors on cultured lymphoblastoid cells was relatively low (106–107 L/M), and the IgE rapidly washed off the cells. Monocytes specifically phagocytosed and lysed IgE-coated 51Cr-labeled Ec. These data provide evidence that Fc receptors for IgE are found not only on mast cells and basophilic granulocytes but also on lymphocytes and monocytes. The affinity of monomeric IgE to the Fc receptors of these cell types is much lower than that to mast cells and basophilic granulocytes. The function of Fcϵ receptors on monocytes is most likely promotion of phagocytosis and lysis of IgE-coated target cells. Fc receptors for IgE on lymphocytes may play a role in the regulation of IgE synthesis.

The Structure and Biology of Human IgD

IgD was first detected in 1965 and characterized as the fourth class of immunoglobulins (Ig) by Rowe & Fahey (1965a, b) through the study of a myeloma protein that could not be typed as IgG, IgM or IgA. Although at that time these authors established that IgD has all structural features of Ig, its role in the immune system is still unknown. There are many reasons for this. IgD is only a minor serum component and antibody activity is not usually found associated with IgD. No IgD secondary biological functions mediated by the Fc fragment have been found (Spiegelberg 1974). Recently, it was discovered that IgD is also a major antigen receptor on bone marrow derived (B) lymphocytes (Rowe et al. 1973) and this has stimulated the new research on the function of IgD that is reviewed in the papers of this volume. Antigenically, the serum IgD and cell bound IgD are closely related; however, it has not yet been demonstrated that they are identical. First, they may differ in that the cell bound IgD probably has an additional structure which is responsible for its persistence in the cell membrane. Second, serum and cell bound IgD may relate to one another as subclasses. The suspicion that prompts this theory originates from the unexplained observation that 90 % of IgD myeloma proteins are of X type (Jancelewicz et al. 1975), whereas the majority of cell bound IgD is of K type (Rowe et al. 1973). The frequency of K and A types of myeloma

The IgE and IgG subclass responses of mice to four helminth parasites

To investigate whether the formation of IgE is linked in vivo to an IgG subclass, mice were infected with four helminth parasites, Nippostrongylus brasiliensis (Nbr), Mesocestoides corti, Taenia crassiceps and Trichinella spiralis, and the changes in the serum levels of the different Ig isotypes as well as the antibody response to M. corti and T. crassiceps antigen extracts were determined by radioimmunoassays. All four parasites induced a concomitant increase of the IgE and IgG1 serum levels and usually a decrease of the IgG2a level. They also induced an increase of the IgM level but had little effect on the IgG2b, IgG3, and IgA serum levels. The specific antibodies to an M. corti antigen extract were mainly of the IgG1 subclass, whereas it was of both IgG1 and IgG2a subclasses to T. crassiceps. Injections of dead M. corti induced an increase of all IgG subclasses and similar levels of IgG1 and IgG2a anti-parasite antibodies. Subcutaneous instead of intraperitoneal infection with T. crassiceps induced higher IgG2a than IgG1 levels and 10-fold lower IgE levels than the natural ip infection; however, despite the greater IgG2a polyclonal response, anti-parasite antibodies were predominantly of the IgG1 subclass. The data demonstrate that natural infection with four different helminth parasites induces a concomitant polyclonal IgG1 and IgE response. These in vivo observations corroborate the recent in vitro findings demonstrating that interleukin-4 induces lipopolysaccharide-activated murine B cells to secrete both IgG1 and IgE, suggesting that the regulation of these two isotypes is linked.

Receptors specific for IgE on rat alveolar and peritoneal macrophages

Abstract Alveolar and peritoneal macrophages (aMφ and pMφ) from normal rats were analyzed for their ability to form rosettes with fixed ox erythrocytes (E o ′) coated with a rat IgE myeloma protein (E o ′-IgE). The macrophages were also examined for rosette formation with E o ′ coated with rat IgG (E o ′-IgG) and fresh ox erythrocytes sensitized with rabbit IgG anti-E o antibodies (E o A). A mean ± SD of 87.0 ± 5.2% aMφ and 56.4 ± 4.2% pMφ from normal Buffalo rats formed E o ′-IgE rosettes. Approximately 85% of the aMφ from Lewis and brown Norway rats also formed E o ′-IgE rosettes. The E o ′-IgE rosettes were inhibited by two different rat IgE myeloma proteins but not by rat or rabbit IgG nor by human IgE. Indicator cells coated with 56 °C heated or reduced and alkylated rat IgE did not form rosettes. Furthermore, heated or reduced and alkylated IgE failed to inhibit E o ′-IgE rosette formation, suggesting that the native structure of rat IgE was necessary for rosette formation. Approximately 80% of both aMφ and pMφ formed rosettes with E o ′-IgG or E o A indicator cells. The E o ′-IgG rosettes were inhibited by rat and rabbit IgG but not rat IgE. Treatment of macrophages with high doses of trypsin abolished E o ′-IgG and E o ′-IgE rosette formation and slightly decreased the percentage of E o A rosettes. The experiments indicate that the majority of rat aMφ and pMφ possess trypsinsensitive receptors for IgE, which are class and species specific.

Immunoglobulin dysregulation in murine graft-vs-host disease: A hyper-IgE syndrome

Immunoglobulin production, particularly IgE, is known to be dysregulated in graft-vs-host disease (GVHD). We examined serum levels of the highly T-dependent Ig isotypes, IgE, IgG1, and IgG2a, in two different mouse models of GVHD. GVHD across minor histocompatibility barriers is produced by injection of B10.D2 spleen cells into 600 rad irradiated BALB/c hosts. Both strains are H2d and mls b, but differ at the minor histocompatibility antigens. As GVHD progresses there is a rapid rise in serum IgE (300-fold) and IgG1 (2.5-fold) with a peak at Day 14. Concomitantly, IgG2a falls. Serum immunoglobulin levels return to normal by 11 weeks. The rise in IgE is abolished by increased (900 rad) recipient irradiation, suggesting that host-derived factors are important. GVHD across major histocompatibility barriers is produced by injection of DBA/2 spleen cells into unirradiated or 600 rad irradiated (B6 x DBA/2)F1 hosts. Only in the irradiated recipients is there severe Ig dysregulation. In this situation there is a 100-fold rise in IgE, and 5- to 10-fold rises in IgG1 and IgG2a. While the results in GVHD across minor barriers suggest stimulation of T helper cells secreting IL-4, the increase in IgE, IgG1, and IgG2a levels in GVHD across major barriers suggests activation of IL-4 and IFN-gamma-secreting T cells. These results indicate that different mechanisms may be operating in these two models of GVH. Murine GVHD can serve as a model for studying dysgammaglobulinemias in general and for hyper-IgE formation in particular.