B lymphocyte sensitivity to IgM receptor ligation is independent of maturation stage and locally determined by macrophage-derived IFN-beta

Compartmentation of B lymphocyte populations is associated with differences in both development stage and sensitivity to Ig (sIg)-dependent triggering. In order to characterize the factors that contribute in setting the level of sensitivity of a B cell, we quantified sIgM-dependent regulation of Ig secretion in purified mature and immature B cells after ex vivo and in vivo modification of their environment. These analyses formally demonstrate that the bone marrow (BM) microenvironment locally induces high B cell sensitivity to sIgM ligation irrespective of differentiation stage. We further provide evidence that BM macrophages create a dominant environment that enhances B cell sensitivity to B cell receptor triggering. Finally, using ex vivo assays as well as type I IFN receptor-deficient mice we show that IFN-beta produced by resident BM macrophages is necessary and sufficient to define B cell sensitivity. Implications of these findings for the understanding of B cell selection processes are discussed.

Neonatal tolerance to alloantigens is induced by enriched antigen-presenting cells

Spleen and bone marrow cells from normal or Rag-1-deficient donors are equally competent in their ability to induce neonatal transplantation tolerance in semi-allogeneic hosts, and the latter are also capable of tolerizing fully allogeneic recipients. Both types of donor cells resulted in comparable levels of haemopoietic chimerism in tolerant animals. Lymphoid hyperactivity, however, was absent in animals tolerized with Rag-1-deficient cells. The authors conclude that neonatal tolerance induced with haemopoietic cells requires no donor lymphocytes, and is thus not the result of deficient antigen presentation. Furthermore, the state of tolerance can be dissociated from the lymphoid hyperactivity that requires donor lymphocytes and is regularly scored in conventionally tolerized animals.

An example of idiotypic mimicry

We have evaluated the impact of transgenic immunoglobulin (TGIg) expression on endogenous antibody repertoires. The transgenic system was chosen as to allow for normal recombination of endogenous Ig genes, secretion of TGIg from early development on, and distinguishing the TGIg from endogenous Ig by several serological markers on the C and V regions of the molecules. The transgenic construct encodes a complete anti-(4-hydroxy-3-iodo-5-nitrophenyl)acetyl (NP) antibody molecule carrying a well-defined idiotype, bearing a lambda 1 light chain and a chimeric heavy chain encoded by a human alpha 2 C region devoid of its membrane exon, and the murine B1.8 VDJ-region. Endogenous antibody repertoires were analyzed in mitogen-driven limiting dilution cultures, in single-cell assays for naturally activated Ig-secreting cells, and in hybridomas derived by direct fusion of spleen cells from unmanipulated animals. The results show that a very high frequency of splenic resting B cells and plasma cells in transgenic animals produce IgM with B1.8-cross-reactive idiotypes. This was confirmed by hybridoma analysis which also established that the levels of transgene expression and of idiotype-positive IgM production by the same cell are not correlated. The affinities of idiotype-positive endogenous Ig varied, but were generally several orders of magnitude lower than the transgene-encoded idiotype. V regions from idiotype-cross-reactive IgM heavy chains showed marked diversity in sequences that were all different from the transgenic B1.8. These results are compatible with idiotypic mimicry resulting from intercellular selection based on degenerate, whole V region reactivities.

The repertoire of serum IgM in normal mice is largely independent of external antigenic contact

Antigen-free (AGF) and germ-free (GF) mice, although essentially free of serum IgG, maintain normal levels of circulating IgM. Using a quantitative immunoblot assay, we have now analyzed the repertoire of serum IgM from AGF, GF, and specific pathogen-free (SPF) BALB/c mice, on large panels of natural antigens from homologous tissues and bacteria. The reactivity profiles were very similar in the three groups of mice. Multiparametric statistic evaluation of the data showed that BALB/c animals, SPF, GF, and AGF mice constitute an homogeneous group with similar immunoreactivity profiles when compared to C57BL/6. Differences between immunoreactivity profiles of GF and AGF mice were observed, but were not statistically significant. These results suggest that the serum IgM repertoire of normal mice is strictly regulated and selected by endogenous ligands.

Differential sensitivity of B lymphocyte populations to IgM receptor ligation is determined by local factors

Ligation of surface IgM on B cells responding to lipopolysaccharide (LPS) suppresses terminal differentiation and high-rate Ig secretion with no effect on proliferation. As shown here, different B cell populations show characteristic mean values of ligand concentration required for 50% inhibition, with Gaussian distributions of sensitivity to IgM receptor ligation that reflect cellular heterogeneity of 'al-or-none' inhibitions in single cells. Differential sensitivity of B cell populations to IgM ligation seems to be locally determined by the cellular environment and unrelated to the 'maturity' of the responding cells. Thus, while long-lived peritoneal B cells are 3- to 5-fold more resistant than splenic B cells, there is no difference in sensitivity between short- and long-lived B cells in the spleen. Furthermore, while B cells in bone marrow and spleen differ in sensitivity by two orders of magnitude, B cells differentiated in vitro from bone marrow pre-B cells are as resistant as splenic B cells. Moreover, bone marrow cell culture supernatants restore a high level of sensitivity in such cell populations. Differential sensitivity to IgM receptor ligation is reproduced by multivalent nominal antigen, in cell populations that show identical dose-response inhibition curves to direct activation of protein kinase C by phorbol esters. We conclude that the level of sensitivity to IgM ligation is independent of the life span or maturity of the B cell, but differentially regulated in vivo by putative tissue factors.

Abnormal T cell selection on nod thymic epithelium is sufficient to induce autoimmune manifestations in C57BL/6 athymic nude mice

To investigate the role of primary T cell repertoire selection in the immunopathogenesis of autoimmune diseases, pure thymic epithelium (TE) from nonobese diabetic (NOD) embryos was grafted into non autoimmune prone newborn C57BL/6 athymic mice. The results show that NOD TE selects host T cell repertoires that establish autoimmunity in otherwise nondiabetic animals. Thus, such chimeras regularly show CD4 and CD8 T cell-mediated insulitis and sialitis, in contrast with syngeneic or allogeneic chimeras produced with TE from nonautoimmune strains. This is the first demonstration that autoimmunity to pancreatic beta cells and salivary glands can be established by the sole alteration of the thymic environment involved in T cell selection, regardless of the nature and presentation of both major histocompatibility complex and tissue-specific antigens on the target organ. These data indicate that T cell repertoire selection by the NOD thymic epithelium is sufficient to induce specific autoimmune characteristics in the context of an otherwise normal host.

Characteristic generated alterations of autoantibody patterns in idiopathic thrombocytopenic purpura

Using a Western blot technique that allows quantitative detection of antibody reactivities to a large number of antigens, serum IgG and IgM antibody repertoires were compared in a group of 19 patients with a diagnosis of idiopathic thrombocytopenic purpura (ITP) and respective healthy controls. The results show that, irrespective of the duration of thrombocytopenia, age of the patients, and type of therapy, all ITP donors share characteristic alterations of serum antibody reactivity patterns on homologous erythrocyte and liver antigens. Multiparametric analyses of the immunoreactivity data readily segregated the groups of ITP and healthy donors. Similar analyses also distinguished ITP sera from those of a group of patients with systemic lupus erythematosus (SLE). We conclude that ITP is an autoimmune disease associated with generalized alterations of antibody repertoires, that may be characteristic enough to allow for diagnosis.

Distinguishable patterns of connectivity in serum immunoglobulins from SLE patients and healthy individuals

Given that normal individuals maintain significant levels of serum autoantibodies that share many characteristics with those found in association with autoimmune diseases (AID), it has been proposed that disease could result from defects in supraclonal regulation, namely deviations of normal patterns of immunoglobulin (Ig) connectivity. Using conventional methods, together with a recently developed technique to quantitatively score a variety of V-region-dependent serum IgG interactions, the authors have now compared serum Ig connectivity in a group of patients with systemic lupus erythematosus (SLE) to healthy controls. The results demonstrate the existence of V-region interactions of serum IgG and IgM in SLE patients and healthy donors, with comparable connectivity titres, diversity and average affinities (microM range), but a wider individual variation and a tendency for higher F(ab')2 directed reactivities in the group of SLE patients. Multivariate statistics analysis of the data derived from reactivity patterns on F(ab')2 subsets, however, distinguished the two groups of donors, and demonstrated a larger dispersion and wider time-dependent variations in the patient population, as compared to healthy controls. The authors conclude that SLE is associated with circulating antibody repertoires that deviate from the patterns and levels of V-region connectivity characteristic of healthy individuals. These findings may shed light on the mechanisms of disease maintenance, and on the basis for the therapeutic effects of normal polyclonal Igs at high doses.

Maternal IgG stimulates B lineage cell development in the progeny

To examine the physiological role of maternal natural IgG antibodies on the development of B lineage cells of the progeny, we have bred homozygous muMT/muMT or heterozygous muMT/+ females to muMT/muMT or muMT/+ males, respectively. We could thus compare normal or B cell-deficient mice born from Ig-deprived (Ig-) or phenotypically normal mothers (Ig+). B cell-deficient progeny of heterozygous mothers contain no detectable serum IgA or IgM, but IgG concentrations that peak at 2 mg/ml by 7-21 days of age, decay after weaning with a half-life of 7 days, and remain detectable for 2 months after birth. At 7 days after birth, muMT/+ progeny born of Ig+ mothers contain two- to threefold higher numbers of bone marrow (BM) pre-B and B cells, and of splenic B cells, compared to mice of the same age born from Ig mothers. In contrast, the former progeny exhibit two to four times lower numbers of Ig-secreting plasma cells in spleen and thymus, and contain sixfold lower serum IgM concentrations. A similar maternal IgG-dependent stimulation of BM B cell precursors is also observed in muMT/muMT progeny. No significant differences were detected between the groups on day 3 after birth, suggesting the requirement for a minimal IgG concentration in the serum.

Instability of natural antibody repertoires in systemic lupus erythematosus patients, revealed by multiparametric analysis of serum antibody reactivities

Recent views on autoimmune diseases invoke generalized but specific perturbations in antibody repertoires, rather than the clonally restricted or non-specific polyclonal alterations proposed thus far. The present experiments analyse serum antibody reactivities in 24 systemic lupus erythematosus (SLE) patients and 17 healthy controls, using a method that quantitatively scores a large number of antibody reactivities and allows for multiparametric statistical analyses. The results show global but relatively specific perturbations in SLE antibody repertoires, and identify novel disease-associated reactivity patterns. Furthermore, a time series analysis of serum antibodies over 3 months demonstrates instability of natural antibody repertoires in individual SLE patients, contrasting with their remarkable conservation in healthy donors. Moreover, the method used clusters controls and patients independently, and might prove of diagnostic value, once large data bases are established.

Targeted disruption of the V(H) 81X gene: influence on the B cell repertoire

We have generated a mutant mouse in which the most D-proximal V(H) gene (V(H)81X) has been disrupted by introducing a neomycin-resistance gene into the V(H)81X exon by means of gene targeting in embryonic stem cells. The mutant mice generated are unable to express the V(H)81X gene but appear to display a normal pattern of B cell differentiation as well as normal numbers of bone marrow and peripheral B cells from fetal life all through ontogeny. They mount normal immune responses to several different antigens tested. In contrast, the distribution of V(H) gene rearrangements in the V(H)7183 family is altered in homozygous mutant mice. Thus, the antibody repertoire of the targeted mice is modified, at least as far as the expression of V(H)7183 genes is concerned.

[History of lymphatic filariasis in Pernambuco. I. Epidemiologic and control aspects]

This paper is a review of lymphatic bancroftian filariasis in the State of Pernambuco. Brazil. It shows that reports have existed since the 1st decade of the century. Knowledge of the disease in several areas during different periods makes a retrospective analyses very interesting, particularly in Great Recife. It is in the city that the epidemiological and control aspects of the diseases are examinations in details.

The age-associated increase in autoreactive immunoglobulins reflects a quantitative increase in specificities detectable at lower concentrations in young mice

Serum immunoglobulins reactive with several autoantigens have been reported to increase with age. The authors have studied the reactivity of serum immunoglobulins from mice between 2 and 24 months of age with antigens present in lysates of syngeneic tissue extracts from young mice. The profile of immunoglobulin binding with the immunoblots of spleen and brain tissue increased progressively with age, showing only minor differences from mouse to mouse and, with one exception, revealing that the age-associated increase in binding of immunoglobulins occurred with antigens with the same migratory position in the immunoblots detectable, at lower concentration, in sera from young mice. Not all sera from older mice had increased immunoglobulin binding when tested with extracts of skin, muscle and liver but those that did expressed increased binding with antigens in all three lysates and with the same profile shown by sera from young mice. These results are consistent with the hypothesis that the age-associated increase in autoreactive immunoglobulins represents a selective increase in autoreactive specificities expressed by serum immunoglobulins from young animals at lower levels.

A model of the immune network with B-T cell co-operation. I--Prototypical structures and dynamics

Hitherto, "second generation" network models of the immune system have all been restricted to B-lymphocytes and the Ig molecules they produce. These models have not so far been able to provide a convincing mechanism for the distinction between a "Central Immune System" (CIS) composed of a connected network of lymphocyte clones which couple with "self" antigens in a tolerant mode, and a "Peripheral Immune System" (PIS) composed of clones with little or no supra-clonal organization and which produce classical immune responses when interacting with "non-self" antigens. Here, we present a new network model which explicitly incorporates B-T cell co-operation. In this model, B-cell activation is dependent on T-cell help, and activated T-cells are down-regulated by engagement of their TCRs by soluble Ig. We discuss the underlying biology on which we base the system of ordinary differential equations which defines the present network model. We then illustrate some basic features of the model by examining several prototypical situations with a small number of clones. Depending on the idiotypic connectivity structure, the model exhibits two distinct modes of coupling with antigens: an "immune response" mode in which T- and B-cell clones grow exponentially; and a "tolerant" mode in which T-cell clones are controlled by inclusion of all TCRs in the repertoire of an idiotypic B-cell network. Finally, we discuss the simplifying assumptions of the present model and argue that its range of validity is indeed the region of the state-space of the system where the discrimination between the CIS and the PIS take place.

A model of the immune network with B-T cell co-operation. II--The simulation of ontogenesis

This paper is based on a new model of the immune network which explicitly incorporates B-T cell co-operation. A major feature of this model is the simplifying assumption that inhibition by anti-TCR soluble Ig is the only possible down-regulatory influence on activated T-cells. This model is capable of coupling with antigens in both an "immune response" mode and a "tolerant" mode. In the present paper, we simulate the ontogenesis of the immune system by metadynamical recruitment of T- and B-cell clones from the thymus and the bone marrow, seeking to identify the conditions under which each of these modes of antigen coupling occurs. Achieving the tolerant mode depends principally on four parameters: a high value of SB, the rate of bone-marrow production of B-cells; a relatively high efficiency of T-help through mIg-TCR recognition compared with (MHC + peptide)-TCR interaction; and a relatively high value of the product PR.NA, where PR is the average probability that an Ig recognizes another molecule and NA is the number of antigens which are present throughout ontogeny. Analysis of the conditions under which these two modes can coexist, shows that this is possible when a sufficiently numerous set of founder antigens couple in a tolerant mode, whereas isolated antigens first presented once development is completed couple in an immune response mode. The present model thus provides a possible mechanism for the distinction (hitherto purely descriptive) between a Central Immune System organized as a network and responsible for tolerance, and a Peripheral Immune System responsible for immune responses.

The self-reactive antibody repertoire of normal human serum IgM is acquired in early childhood and remains conserved throughout life

The authors have used a quantitative immunoblotting technique to analyse the antibody repertoire of IgM in cord blood and in the serum of young children, young adult males and aged males directed towards antigens in homologous tissues utilized as sources of self antigens. The reactivities of IgM with self antigens exhibited striking homogeneity and invariance among newborns. Self-reactive IgM repertoires of children, young adults and aged males were markedly conserved among individuals and comprised most of the anti-self reactivities that prevailed in neonates. Reactivities of IgM with bacterial antigens showed a high degree of homogeneity among newborns but were more diverse in children, young adults and elderly individuals. Diversity of IgM reactivities with self and non-self antigens did not vary significantly with aging. Principal component analysis (PCA) and linear discriminant analysis (LDA) of the data discriminated between self-reactive IgM repertoires of newborns and children, but failed to discriminate between repertoires of children, young adults and aged males. The data indicate that the self-reactive antibody repertoire of IgM differentiates during the first years of life and remains relatively constant thereafter.

Establishment of tissue-specific tolerance is driven by regulatory T cells selected by thymic epithelium

Grafts of thymic epithelium (TE) rudiments restore T cell development and function in allogeneic athymic mice. These TE chimeras are specifically tolerant to grafts of peripheral tissues (e.g. skin and heart) from the TE donor strain, although they harbor peripheral immunocompetent T cells capable of rejecting those grafts. Initial analysis has shown that TE chimeras also harbor TE-selected CD4 T lymphocytes that inhibit graft rejection by tissue-reactive T cells in immunocompetent recipients. Peripheral tolerance in TE chimeras is thus maintained by dominant mechanisms dependent on regulatory CD4 T lymphocytes. Here we show that TE-selected regulatory T cells recruit nontolerant tissue-reactive CD4 and CD8 T cells to express similar regulatory functions. Only recent thymic emigrants, but not peripheral resident mature T cells are susceptible to this process of functional education, which also requires exposure to specific antigens and occurs entirely in the periphery. We propose that these mechanisms play a major role in establishing and maintaining natural self tolerance to tissue-specific antigens.

Ultrasonographic evidence of abnormal lymphatic vessels in young men with adult Wuchereria bancrofti infection in the scrotal area

PURPOSE

We determined the prevalence and magnitude of dilatation of the lymphatic vessels of the spermatic cord in men infected with Wuchereria bancrofti, which is known major cause of hydrocele in the tropics.

MATERIALS AND METHODS

Scrotal ultrasound was performed with a 7.5 MHz, transducer in 78 men from Recife, Brazil (endemic for filariasis) and in 15 from a nonendemic area.

RESULTS

Among men from Recife the lymphatic vessels were dilated (1.3 to 15.0 mm., mean 3.8) at the location of the adult worm. Vessel diameter was not associated with hydrocele.

CONCLUSIONS

Lymphatic dilation was observed in all men with ultrasonographically detectable W. bancrofti infection, even those who were asymptomatic.

Ultrasonographic assessment of the adulticidal efficacy of repeat high-dose ivermectin in bancroftian filariasis

Since diethylcarbamazine, the drug recommended for treatment of lymphatic filariasis, seems only partially effective against the adult worm, intense interest persists in identifying a macrofilaricidal drug for this infection. To evaluate directly in vivo the macrofilaricidal activity of repeat high-dose ivermectin, 15 men who had living adult Wuchereria bancrofti detected in the scrotal area by ultrasound were treated with 400 micrograms/kg of ivermectin at 2-week intervals for 6 months (total dose, 4.8 mg/kg). Serial ultrasound examinations were performed before, during, and for 6 months after treatment. Profound suppression of microfilaraemia followed the first dose of ivermectin, but movements characteristic of the adult worm on ultrasound remained unchanged both in location and pattern. Even when given in total doses of 4.8 mg/kg, ivermectin appears to have no observable activity against adult W. bancrofti, although its ability to suppress microfilaraemia makes it potentially useful for the control of lymphatic filariasis.

Murine acariasis. II. Immunological dysfunction and evidence for chronic activation of Th-2 lymphocytes

The authors describe the immunological profile of BALB/c mice with Mite-Associated Ulcerative Dermatitis (MAUD)-like disease, due to Myocoptes musculinus (Koch 1844) infestation. The disease probably involves allergic mechanisms and is characterized by erythematous and pruritic skin lesions, widespread hair loss, lymphadenopathy, lymphocytopenia, granulocytosis and wasting. Affected individuals had much reduced numbers of pre-B and B cells in bone marrow and B cells in blood; decreased T-cell numbers in peripheral lymphoid organs and blood; hypergammaglobulinaemia with selective increases of IgG1, IgE and IgA, and depletion on IgM and IgG3, the same isotype distribution being detected in splenic plasmocytes; qualitative modifications of the serum antibody reactivity pattern; and increased production of IL-4 with decreased IL-2 production after in vitro polyclonal stimulation of T cells. Taken together, these results suggest that infestation by M. musculinus in BALB/c mice leads to a significant immunological disorder resulting in a T-helper-2 (Th-2) type response, with marked systemic consequences. This pathological condition may thus provide a useful model system for the immunobiological perturbation associated with chronic allergic disease.

Studies on the periodicity and intravascular distribution of Wuchereria bancrofti microfilariae in paired samples of capillary and venous blood from Recife, Brazil

We examined the periodicity and intravascular distribution of Wuchereria bancrofti microfilariae (mf) and determined the effect of these parasite properties on the accuracy of blood filming and filtration methods for diagnosis of bancroftian filariasis in the endemic area of Recife, Brazil. Microfilariae in both venous and capillary blood exhibited a nocturnal periodicity pattern with a relatively high amplitude. Overall, capillary blood contained approximately 1.25 times the number of mf present at the same time in the same volume of venous blood. However, the ratio of mf present in capillary and venous blood varied over a 24-hour period, so that the fewest mf were present in the capillary bed of the skin at the time when biting activity of the local Culex vector is the lowest. Twenty or 60 microliters blood films did not reliably detect carriers with fewer than 100 or 60 mf/ml venous blood, respectively, and were thus inadequate for the identification of low density mf carriers. In contrast, all carriers with > 1 mf/20 or 60 microliters blood smear at night could be identified during daytime hours by filtration of 1 micromilligram venous blood.

Histological evidence for adulticidal effect of low doses of diethylcarbamazine in bancroftian filariasis

The ability of diethylcarbamazine (DEC) to kill adult Wuchereria bancrofti worms was evaluated by examining lymphatic nodules formed after treatment with 4 different treatment schedules of 193 males living in the endemic area of Greater Recife, Brazil. Lymphatic nodules appeared in the spermatic cord or upper extremities in 43 of 138 microfilaraemic individuals, in 3 of 30 amicrofilaraemic patients with filarial disease manifestations, and in 1 of 25 asymptomatic amicrofilaraemic residents of the endemic area treated with DEC. Fourteen of these nodules were surgically removed 10-150 d after the start of treatment. Regardless of the DEC dosage and schedule used, all nodules contained damaged and degenerating adult worms. An exuberant granulomatous process with large numbers of eosinophils and progressive fibrosis gradually developed around the dead parasites. The mechanism(s) by which DEC killed adult W. bancrofti could not be determined.

Quantitative analysis of multiple V-region interactions among normal human IgG

There is to date no quantitative method for scoring putative V-region interactions among serum antibodies, and the available qualitative techniques are not amenable to routine utilization. This deficit may explain the paucity of observations on the characteristics of the immune network, in contrast with the multiplicity of phenomenological descriptions on idiotype regulation. We describe here a novel methodology that uses isoelectric focusing (IEF) to resolve human F(ab')2 preparations from large pools of normal serum IgG into multiple bands, and computer-aided data processing to analyze interactions between the resulting blotted proteins and normal serum IgG from individual donors. Our results show that in all normal human sera tested, there are IgG-mediated interactions with a large number of IEF fractions of human F(ab')2. These interactions are V region specific, as assessed by inhibition experiments and by lack of binding of IgG monoclonal antibodies, and are characterized by average affinities that are in the micromolar range, as measured by surface plasmon resonance.

Ig-isotype patterns of primary and secondary B cell responses to Plasmodium chabaudi chabaudi correlate with IFN-gamma and IL-4 cytokine production with CD45RB expression by CD4+ spleen cells

In this work, the authors analysed T and B lymphocyte subsets and cytokine production in the spleen of BALB/c mice during polyclonal lymphocyte activation (primary infection) and parasite-specific response to Plasmodium chabaudi chabaudi (secondary infection). The secondary response was evaluated in fully immunoprotected animals, 60 days after a chloroquine-cured infection. The authors observed that in polyclonal lymphocyte activation antibody-secreting cells of all isotypes increased, with predominance of IgG2a and IgG3 classes. At that time, IFN-gamma was largely produced, but IL-4/IL-5 were just slightly enhanced. In mice re-infected after 60 days, the Ig-isotype pattern was restricted to IgG1 and only IL-4/IL-5 were produced. In both responses, however, the levels of IL-2 were greatly reduced, while those of IL-10 were enhanced to similar levels. The different involvement of Th1 and Th2 cells in both responses was confirmed through analysis of CD45RB expression by CD4+ cells. The authors observed that CD45RBhigh cells were the major CD4+ subpopulation in primary infected mice, while CD45RBlow cells predominated in 60 days re-infected animals. Moreover, the great majority of activated (large) CD4+ cells in the primary infection belonged to the CD45RBhigh subset, while after reinfection most of the CD4+ large had a CD45RBlow phenotype.