Further evidence for coelomic-associated B lymphocytes

Previous observations indicate that "CD5 B lymphocytes" are preferentially clustered in gut-related mesenchymal areas, such as peritoneum, thymus and tonsils. We have now found that pleuropericardial spaces contain an homogeneous population of large-sized, noncycling, nonsecretory B cells, expressing very high levels of surface IgM, little or no IgD, Mac-1 and low levels of B220. This phenotype and the over-representation of some antibody clonotypes suggest that the pleuropericardial cavity contains a pure "CD5 B cell" population. In all mouse strains analyzed, however, many of these cells are CD5-. These findings, together with the common origin of peritoneum and pleural layers in the primitive coelomic cavity, suggest that such B cells differentiate locally from intraembryonic precursors; we propose to designate them as "coelomic", to distinguish them from "stromal", bone marrow-derived B cells.

Immune networks: getting on to the real thing

After some ten years of faltering development, the network approach in immunology is finally heading toward steady ground. At a recent international workshop (*), experimentalists and theoreticians discussed some of the latest developments, including an impressive array of novel results and applications to fundamental properties of biological immune networks: connectivity, patterns of dynamic activity, ontogenesis, and tolerance.

[Clinical manifestations of lymphatic bancroftian filariasis]

A review of clinical manifestations of bancroftian filariasis, based on the literature and in the authors' experience, suggests a general classification in to six groups: 1) Normal endemics; 2) Individuals bearing microfilaremia; 3) Acute manifestations; 4) Chronic manifestations; 5) Tropical Pulmonary Eosinophilia; 6) Controversial forms. An overview on diagnostic procedures and the immunologic relationship between host and parasite was made in each group. Final considerations about treatment was also considered.

Major histocompatibility complex-linked and T cell-dependent selection of antibody repertoires. Quantitation of I-E-related specificities in normal mice

Autoreactive B cell repertoires with major histocompatibility complex (MHC) class II (I-E)-related specificities were investigated by quantitating frequencies of specific B lymphocyte clonal precursors in unmanipulated normal and athymic BALB/c mice and in I-E-negative, MHC-congenic BALB.B10 mice. Clonal culture supernatants containing anti-I-E antibodies were identified by their selective binding to I-Ek alpha Ed beta-transfected fibroblasts, and those containing anti-anti-I-E antibodies were detected by their selective binding to anti-I-E monoclonal antibodies. Analysis of splenic B lymphocytes from BALB/c mice revealed high frequencies of both specificities in the compartment of large, naturally activated cells, but not among small, resting lymphocytes. The selection of such clones was found to be MHC linked because of their absence in BALB.B10 mice, and T cell dependent because of their reduced frequency in athymic BALB/c mice. The positive selection of V regions representing complementarities and mimicries of self-class II antigens may suggest a set of mechanisms participating in the maintenance of natural tolerance.

Differential binding of natural monoclonal antibodies to the surface of fixed or living cells

A few hundred monoclonal antibodies derived from normal mice were tested for binding to cell surface antigens in one T-cell hybridoma and one I-Ek-transfected fibroblast cell line. The assay, which is suitable for large screenings, used glutaraldehyde-fixed cells followed by immunoenzymatic detection of immunoglobulin. Of the 331 antibodies tested, 75 showed significant binding, not only on these cells, but also on a macrophage, fibroblast, thymoma, and pre-B cell line, and on normal syngeneic and allogeneic thymocytes. If the assay was modified so as to use live cells in a simplified ELISA on living cells, only 10 of 253 antibodies were found to be positive with the T-cell hybridoma line and 7 with the transfected fibroblast cell line. In both sets of conditions, about 75% of the positive antibodies were found to be 'multireactive' after being tested on a panel of antigens. In contrast, conventional 'immune antibodies' to cell surface antigens could be tested by routine methods in either type of assay. We conclude that, while glutaraldehyde fixation does not affect the reactivity of conventional antibodies, this technique is inappropriate for testing the binding of natural antibodies to cell surface antigens.

Suppression of antibody responses to the acetylcholine receptor by natural antibodies

Some relationships between "natural" physiological autoreactivity and antibody responses against the acetylcholine receptor (AChR) were investigated. Collections of unselected monoclonal antibodies were derived from nonmanipulated newborn mice of susceptible (BALB.B) and resistant (BALB/c) mouse strains, and screened for reactivity with heterologous AChR. Five in 200 BALB/c but none in 200 BALB.B clones were found reactive. Four of these anti-AChR antibodies were analyzed for connectivity to nine other antibodies in the same collection, and three of them found to react with a particular natural anti-idiotype. The functional in vivo significance of such natural idiotypic complementarities in the anti-AChR response could then be investigated. Treatment of BALB/c newborn animals with low (100 ng) or high (100 micrograms) doses of natural anti-idiotype significantly suppressed their anti-AChR antibody response when immunized as adults. The utilization of natural anti-idiotype reagents with broad reactivity patterns might overcome the known idiotype heterogeneity of the autoimmune antibody response to AChR and provide a strategy in prophylactic and therapeutic manipulation of disease development.

Evidence for a functional idiotypic network among natural antibodies in normal mice

We monitored in normal adult BALB/c mice the serum concentrations of four natural IgM antibodies, two of which show idiotypic complementarity in in vitro assays. In each individual, serum concentration of all four idiotypes were found to fluctuate in complex dynamical patterns with low correlation. The spectral power of some such patterns was found to be compatible with the existence of a chaotic regime. Groups of normal adult mice were injected intravenously with low (10 ng) or moderate (10 micrograms) doses of either of the two complementary idiotypes in saline. This treatment resulted in a pronounced inhibition of the fluctuation in the serum concentration of both complementary idiotypes for periods up to 3 months. Such compensations were not detected for the two unrelated natural idiotypes and were specifically induced, for they did not occur following the injection of unrelated antibodies. These results indicate the functional operation of an idiotypic network among natural antibodies.

Ontogenic development of autoantibody repertoires in spleen and peritoneal cavity of normal mice: examples of T cell-dependent and -independent reactivities

The ontogenic development of B cell clonal precursors (BCP) reactive to bromelain-treated, syngeneic erythrocytes (BrMRC) and to single-stranded DNA has been studied by limiting dilution of both spleen and peritoneal cells. It was found that the frequency of anti-BrMRC BCP in the spleen is very low up to 4 weeks of age and slowly increases thereafter, to reach adult levels by 6-10 weeks. In the peritoneal cavity, no such BCP can be found before 2 weeks, but they occur at a very high frequency already by 3 weeks of age. Injection of adult, normal syngeneic T cells at birth has no apparent effect on the representation of anti-BrMRC BCP in the peritoneal cavity, but brings these to adult levels or even higher in the spleen already at 3 weeks of age. Accordingly, adult athymic (nude) mice contain normal frequencies of BrMRC-specific BCP in the peritoneal cavity but are devoid of such clones in the spleen. In contrast, the frequency of anti-DNA BCP is very high throughout postnatal development in both spleen and peritoneal cavity, of normal and athymic mice, in both resting and naturally activated splenic B cell compartments, and it is independent of T cell transfers into nude animals. These results indicate the role of T cells in the establishment of some clonal specificities in the adult, splenic autoreactive B cell repertoire.

Indiscriminate representation of VH-gene families in the murine B lymphocyte responses to Trypanosoma cruzi

The utilization of the nine major homology families of VH-genes was quantitated in the B lymphocyte response to Trypanosoma cruzi infection of C57BL/6 mice. Normal and infected mice at various times after parasite inoculation were compared for VH-gene distribution of CFU-B produced by activated blasts recovered from spleen and lymph nodes, and for relative hybridization of total spleen RNA with each of the family probes. T. cruzi infection results in large increases of splenic RNA in the various homology families, and the numbers of activated CFU-B, reflecting the massive B lymphocyte responses. In acute phase, all nine families are expressed in roughly the same proportions as in normal mice, whereas in chronic infection, B cells expressing S107 and 7183 VH-genes might be preferentially stimulated. These results establish the polyclonal nature of the host response to T. cruzi infection.

Elevation of laminin and beta-subunit of prolyl 4-hydroxylase in the sera of human subjects with Schistosomiasis mansoni

Serum levels of several markers for liver fibrosis were measured utilizing three groups of human subjects related with schistosomiasis mansoni in northeast Brazil; (1) 20 Schistosoma mansoni egg-positives, who have never been administered with anti-schistosomal drugs, (2) 29 egg-negative inhabitants in the endemic area of schistosomiasis, and (3) 23 egg-negative Japanese immigrants in the non-endemic area. None of these sera were positive for antibody to the surface antigen of human hepatitis B (HBs) and circulating HBs antigen. There was no significant difference in the serum levels of N-terminal peptide of procollagen type-III between the egg-positive subjects and either of the egg-negative Brazilian or Japanese immigrants, whereas the mean value of serum laminin significantly increased in the egg-positive subjects. A significantly higher concentration of serum immunoreactive beta-subunit of prolyl 4-hydroxylase (IR beta PH) was also observed in the egg-positive subjects only in comparison with that of the egg-negative Brazilian. Serum laminin and IR beta PH concentrations of the egg-positive subjects did not correlate with the absorbance of enzyme-linked immunosorbent assay (ELISA) which utilized crude antigens isolated from schistosome adults or eggs. No significant difference in these two parameters was observed between two subgroups of the egg-negative Brazilian or Japanese immigrants divided according to the serological data by ELISA. These findings suggest that serum laminin and IR beta PH levels are worth further evaluation for their usefulness as the marker for liver fibrosis in schistosomiasis.

The relationship between connectivity and tolerance as revealed by computer simulation of the immune network: some lessons for an understanding of autoimmunity

According to a classical, antigen-driven view of the immune system, autoimmunity is due to the presence of self-reactive lymphocyte clones which have not been eliminated. However, computer simulations of the immune network show that the greater the degree of connectivity of a clone, the greater its degree of tolerance to chronic antigenic stimulation. This tolerance does not correspond to an absence of response on the part of the system as a whole. On the contrary, stimulation by a 'tolerogenic antigen' results in widespread modification and overall activation of the whole network. This suggests that on an autopoietic network view of the immune system, autoimmunity arises not because of the presence of self-reactive clones, which is completely normal, but because such clones are inadequately connected to the network. This amounts to a complete reversal in perspective, whose significance for the clinical treatment of autoimmunity and the future of immunology is discussed.

Immunoglobulin VH gene expression in Ly-1+ and conventional B lymphocytes

Lymphocyte populations in which Ly-1 B cells are differentially represented were studied for the expression of ten VH gene families, either by an RNA colony blot assay or by in situ hybridization of single cells, in BALB/c and C57BL/6 mice. The comparisons of cells from lymph nodes, Peyer's patches and adult spleen (poor in Ly-1 B cells) with cells from peritoneal cavity and neonatal spleen (rich in Ly-1 B cells) were confirmed by the analysis of adult peritoneal Ly-1- and Ly-1+ B cells sorted on the fluorescence-activated cell sorter. The results indicate that the peritoneal Ly-1+ B subset uses the whole spectrum of known VH gene families, and shows a preferential utilization of CP12 VH genes, most likely as a result of a selective process during life.

Indiscriminate representation of VH-gene families in the murine B lymphocyte responses to Trypanosoma cruzi

The utilization of the nine major homology families of VH-genes was quantitated in the B lymphocyte response to Trypanosoma cruzi infection of C57BL/6 mice. Normal and infected mice at various times after parasite inoculation were compared for VH-gene distribution of CFU-B produced by activated blasts recovered from spleen and lymph nodes, and for relative hybridization of total spleen RNA with each of the family probes. T. cruzi infection results in large increases of splenic RNA in the various homology families, and the numbers of activated CFU-B, reflecting the massive B lymphocyte responses. In acute phase, all nine families are expressed in roughly the same proportions as in normal mice, whereas in chronic infection, B cells expressing S107 and 7183 VH-genes might be preferentially stimulated. These results establish the polyclonal nature of the host response to T. cruzi infection.

The immune response to bacterial dextrans. VI. No correlation between the frequency of cells expressing a major anti-dextran idiotype and the idiotype profiles of specific antibody responses

C57BL/6 mice respond to Dextran B512 (Dex) with a predominant idiotype (Id) (17-9) while no such Id-positive antibodies are identified in the specific antibody response of BALB/c mice. We used limiting dilution systems to determine the absolute frequencies of clonal B-cell precursors producing the 17-9 Id in these two mouse strains and analysed the correlation between Id-expression and antibody activity at the clonal level. The results show very similar frequencies of anti-Dex and Id-positive B cells in both strains, but C57BL/6 mice contained fourfold higher frequencies of Dex-specific clonal precursors which are Id-positive. This kind of clone, although not used in the specific response of BALB/c mice, constitute roughly 20% of their anti-Dex repertoire and they are readily induced in this strain. Thus, immunization of both strains with anti-idiotypic antibodies results in the production of Id-positive anti-Dex antibodies with serum titres that directly correlate with precursor frequencies. The results show, therefore, that the section of clonal repertoires utilized in a primary immune response varies with the immunogen, even if thymus-independent. These observations are discussed in the context of the genetic controls of anti-Dex antibody responses and on the general question of the utilization of available antibody repertoires in immune responses.

Expression of VH11-gene family in hybridoma collections from peritoneum and spleen: differential correlation with BrMRBC reactivity

Hybridoma collections from spleen or peritoneal cells of newborn or adult individuals were screened by RNA hybridization for expression of the VH11-gene family using a V-region probe VCP12, which encodes anti-BrMRBC antibodies. No VH11 expression was observed in hybridomas derived from newborn spleen cells in either BALB/c, NZB or (CBA/N x BALB/c) F1 mice (0/93). Adult NZB and BALB/c spleen cell collections contained only one hybridoma expressing VH11 (1/242). Interestingly, however, the VH11-positive hybridoma showed no anti-BrMRBC reactivity, while one anti-BrMRBC clone in the same collection expressed a Q52 VH gene. In contrast, hybridomas derived from peritoneal cells showed an absolute correlation between expression of VH11 genes and anti-BrMRBC reactivity (15/32). The high expression in the peritoneal cavity of such cells is likely the result of local positive selection.

A model system for the analysis of B-cell activation and effector T-cell functions. T cell-dependent B-cell responses facilitated by anti-I-A antibodies

We have attempted to develop an in vitro system where polyclonal B lymphocyte responses could be induced in 'antigen-like' conditions, that is, where surface immunoglobulin-dependent binding mediates interaction with a mitogen. Monoclonal anti-mu and anti-delta antibodies were covalently bound to lipopolysaccharide (LPS) and these complexes were shown to display mitogenic activity. Polyclonal plaque-forming cell (PFC) responses, however, were diminished in cultures stimulated by anti-mu-LPS (but not by anti-delta-LPS) indicating that 'anti-mu inhibition' of terminal B-cell differentiation also applies to 'specific' antibody responses. Moreover, the analysis of the functional activity of monoclonal antibodies to major histocompatibility complex (MHC) class II molecules revealed a surprising synergy between low, non-stimulatory concentrations of anti-mu-LPS (but not anti-delta-LPS) with anti-I-A antibodies. These responses are T-cell dependent and synergy with anti-mu-LPS conjugates can also be obtained with 'naturally' activated CD4+ cells isolated from normal donors. A model of molecular and cellular interactions was derived, which accounts for the present findings and is applicable in antigen-dependent lymphocyte collaboration.

Transplantation tolerance correlates with high levels of T- and B-lymphocyte activity

Mice tolerized (treated to make them tolerant) at birth to transplantation antigens by injection of semiallogeneic cells contain very high numbers of activated T and B lymphocytes in their spleen. Lymphoid hyperactivity correlates with the tolerant state: it is present only in animals accepting skin allografts. Tolerized mice that reject the allogeneic skin graft have approximately the same numbers of total and activated lymphocytes as normal mice. The high level of lymphocyte activation in tolerant mice persists for up to 1 year of age, although it declines with age, and is markedly increased by a secondary allograft. The magnitudes of both primary and secondary tolerant responses are significantly higher than the immunological response of a normal mouse rejecting the same type of allograft. These observations contradict concepts of clonal deletion or anergy as the basis of neonatally induced transplantation tolerance and may contribute additional approaches to experimentation and control of transplantation reactions.

Preferential expansion of Ly-1 B and CD4- CD8- T cells in the polyclonal lymphocyte responses to murine T. cruzi infection

Acute murine infection with T. cruzi results in polyclonal lymphocyte responses manifested by blast transformation of a large fraction of B, CD4+, and CD8+ cells. We describe here the finding of significant increases in the splenic representation of minor populations, Ly-1 + B cells and CD4-CD8- T cells. These lymphocyte populations might play an important role in the host response, as shown by T. cruzi infection of hosts that had been lethally irradiated and reconstituted with autologous bone marrow. Under these conditions, the splenic polyclonal PFC responses are nearly abrogated, and not restored by the transfer of syngeneic peritoneal cells which, however, reconstitute T15 idiotype production in the same hosts. Control levels of PFC responses, however, are reconstituted by transfer of syngeneic splenic T cells. Since bone marrow-reconstituted animals contain normal numbers of CD4+ and CD8+ T cells which are actually activated by infection, these results suggest the participation of other T cell populations in the host response to infection, as also suggested by the marked increases in T cell receptor gamma and delta messages detected in the spleen of infected animals. The implications of these findings in immunopathology of Chagas' disease are discussed.

Idiotype-specific regulation might contribute to specific unresponsiveness in dextran-primed mice

Priming of adult responder mice with optimal immunogenic doses of dextran alpha, 1-6 results in reduced antibody responses to secondary antigenic challenge. We have now quantitated dextran-specific clonal precursors in the large and small B-lymphocyte compartments within several days or several months after priming with either dextran or antiidiotypic antibodies directed to a dominant idiotype of C57BL/6 mice which accounts for more than 50% of the antibody response. The results show that "secondary unresponsiveness" correlates with idiotype-directed depletion of the appropriate specificities from the immunocompetent resting B-cell pool.

Differential L chain expression in the antibody responses to phosphorylcholine of adult bone marrow or peritoneum-derived B lymphocytes

Lethal irradiation of adult BALB/c mice followed by reconstitution with autologous bone marrow results in loss of T15 Id and IdX expression in the responses to phosphorylcholine (PC) and alpha(1-3)-dextran, respectively. T15 Id, but not IdX expression can be reconstituted with low numbers of syngeneic, T cell-depleted peritoneal resident cells. All three groups of mice produce comparable titers of specific anti-PC and anti-dextran antibodies. The inability of adult bone marrow-reconstituted BALB/c mice to produce T15 Id+ antibodies is not due to differential VH-gene expression in bone marrow or peritoneum-derived B cells. Thus, the levels of T15 VH in total serum Ig and in anti-PC antibodies are similar in all groups of mice. Furthermore, IEF patterns of T15 VH-associated L chains directly demonstrate differential Vk repertoire expression in bone marrow and peritoneum-derived B cells.

Differential L chain expression in the antibody responses to phosphorylcholine of adult bone marrow or peritoneum-derived B lymphocytes

Lethal irradiation of adult BALB/c mice followed by reconstitution with autologous bone marrow results in loss of T15 Id and IdX expression in the responses to phosphorylcholine (PC) and alpha(1-3)-dextran, respectively. T15 Id, but not IdX expression can be reconstituted with low numbers of syngeneic, T cell-depleted peritoneal resident cells. All three groups of mice produce comparable titers of specific anti-PC and anti-dextran antibodies. The inability of adult bone marrow-reconstituted BALB/c mice to produce T15 Id+ antibodies is not due to differential VH-gene expression in bone marrow or peritoneum-derived B cells. Thus, the levels of T15 VH in total serum Ig and in anti-PC antibodies are similar in all groups of mice. Furthermore, IEF patterns of T15 VH-associated L chains directly demonstrate differential Vk repertoire expression in bone marrow and peritoneum-derived B cells.