Bendazac decreases in vitro glycation of human lens crystallins. Decrease of in vitro protein glycation by bendazac

Bendazac has been used as an anti-cataractogenic drug. It has been reported that this acts by preventing protein denaturation. In this study the ability of bendazac to inhibit in vitro glycation of human lens crystallins was evaluated. Possible effects of bendazac were detected by incubation of WS crystallins with the reducing sugars glucose and fructose. The efficiency of bendazac was evaluated by means of selected parameters including: browning, glycation (measured as tyrosine content) and specific NTP-fluorescence. The results showed clearly that bendazac (bendazac L-lysine and sodium) inhibits the early stages of protein glycation, as well as the formation of fluorescent advanced glycation products. Bendazac lysine (20 mM) proved to be more effective in inhibiting fluorescence development (67% inhibition) that the corresponding sodium salt (35% inhibition). No significant differences were found with respect to furosine levels; about 40% inhibition was produced with either bendazac lysine or sodium salt bendazac clearly inhibits glycation of human lens crystallins, as can be efficiently monitored by following specific changes in lens protein fluorescence. These results may constitute a new and relevant therapeutic approach to monitoring cataract development.

The 1993 epidemic of dengue fever in Mangalore, Karnataka state, India

An epidemic of febrile illness with hemorrhagic manifestations occurred in certain parts of Mangalore city, Karnataka state, India, from the last week of July 1993. The epidemic reached its peak by mid-August and then started declining. Sporadic cases, however, continued to occur till early December. About 200 cases were reported covering all age groups and both sexes. The cases presented with pyrexia, myalgia, arthralgia and headache. Palatal petechiae, magenta colored tongue with central coating, maculopapular rash and facial flush were observed as classical signs. The tourniquet test was positive in 12% of the cases. Hemorrhage was observed in the form of epistaxis (2 cases), subconjunctival hemorrhage (2 cases) or purpura (3 cases). There were no deaths which were attributable to the epidemic. Five strains of dengue (DEN-2) virus were recovered from the acute-phase sera. Dengue virus-specific IgM type of antibodies were detected in 29/116 (25%) sera. Breeding of Aedes aegypti was observed in some of the areas where cases had occurred. No virus was isolated from any of the field-caught Ae. aegypti mosquitos.

Regulatory T cells in thymic epithelium-induced tolerance. I. Suppression of mature peripheral non-tolerant T cells

Athymic mice grafted at birth with allogeneic thymic epithelium (TE) display life-long tolerance to tissue grafts of the TE donor strain, in spite of harboring peripheral T cells capable of rejecting those grafts. Tolerance is maintained in these chimeras by TE-specific regulatory CD4 T cells. We presently address the quantification and the mechanisms of this dominant tolerance process. C57BL/6 mice containing variable but defined numbers of peripheral, resident T cells received cell transfers of graded numbers of peripheral T cells from B6(BALB E10) chimeras (C57BL/6 nude mice grafted with TE from 10-day-old BALB/c embryos), resulting in a series of animals containing a wide range of donor (tolerant) versus host (non-tolerant) T cell chimerism. Increasing the relative representation of donor T cells results in a progressive delay in the rejection of BALB/c skin grafts, life-long tolerance being achieved at a ratio of tolerant and non-tolerant T cell populations of 1. In recipients displaying full tolerance, graft-reactive non-tolerant T cells were not deleted, anergized or committed to noninflammatory functions. Thus, sorted host T cells from tolerant recipients readily rejected BALB/c skin grafts upon transfer to immunodeficient animals. Finally, measurements of "helper" and inflammatory activities, as well as interleukin-4 and interferon-gamma production, failed to discriminate between T cell populations from tolerant and non-tolerant animals after specific in vitro stimulation. We conclude that: (a) TE-selected regulatory T cells can suppress, in a quantitative manner, in vivo T cell responses against major and minor histocompatibility antigens expressed by the TE and, (b) this suppressive activity neither inactivates mature non-tolerant T cells, nor does it seem to drive their differentiation along noninflammatory pathways.

[Abdominal involvement in neurofibromatosis type 1]

Neurofibromas are benign tumours that arise from neuroectodermal tissues. They may occur as solitary lesions, or multiple, then referred to as neurofibromatosis, or von Recklinghausen's disease. We report on a 27-year old patient with large involvement of many nerve trunks and plexus (elephantiasis nervosa), responsible for bowel obstruction and anuria.

Urban levels of air pollution increase lung responsiveness in rats

This study was designed to investigate if animals exposed to urban levels of air pollution develop pulmonary hyperresponsiveness and to test if this change was reversed after moving the animals to a nonpolluted environment. One hundred twenty male Wistar rats were kept in (a) São Paulo (polluted environment) for 3 months (SP3); (b) Atibaia (clean region), for 3 months (A3); (c) São Paulo for 3 months and then Atibaia for a further 3 months (SPA6); (d) Atibaia for 6 months (A6). After the exposure period, the rats were submitted to dose-response curves to inhaled methacholine. Older animals (SPA6 and A6) had lower responses to methacholine in terms of respiratory system resistance when compared to the animals studied after 3 months of experiment (SP3 and A3). However, the response in terms of respiratory system elastance of the SP3 group was significantly (P = 0.0004) greater than those of the other three groups. Our results suggest that the environmental conditions of the large urban centers can induce pulmonary hyperresponsiveness in rats that can be reversed when the animals are removed to a nonpolluted area.

Myocarditis in enteric fever

1. Myocarditis in the course of enteric fever is a common occurrence. In a series of 100 bacteriologically or serologically proved enteric fever, we found 7 cases with clinical evidence of myocarditis and 46 cases with ECG evidence of myocarditis. 2. Commonest ECG abnormality was Q-Tc prolongation (29%) followed by ST-T changes (20%) bundle branch block (7%) first degree A-V Block (%) and arrhythmia (2%). 3. All the ECG changes were transient except bundle branch block which persisted in 3 cases. 4. Those with other systemic complications had a higher chance of having myocarditis (P < 0.01). 5. Autopsy evidence of myocarditis was found in 2 cases. With our results, it is obvious that ECT must be recorded in all cases of enteric fever. Those with ECG changes must be observed carefully for clinical evidence of myocarditis. All these patients must have absolute bed rest. Judicious use of corticosteroids is indicated in selected cases of selected cases of severe myocarditis. Diuretics are indicated in cases with evidence of congestive cardiac failure.

Prospective study of renal transplant infections in 50 consecutive patients

A prospective study of the frequency, timing, etiology and risk factors of infections in renal transplant recipients during the first year after transplantation was conducted in 50 consecutive patients. Neither prophylaxis with trimethoprim-sulfamethoxazole nor antiviral prophylaxis was administered. Two hundred twenty-eight episodes of infection were registered (4.5 per patient), 19 of which were severe. Forty-seven percent of all infectious episodes occurred during the first two months after transplantation. The more frequent infections were bacterial (64%), viral (22%) and fungal (11%). Escherichia coli was the most common agent isolated (n = 36), followed by cytomegalovirus (n = 32). Urinary tract infections were most common (n = 144), especially asymptomatic bacteriuria (n = 106). Surgical reintervention and the use of anti-lymphocytic globulins were associated with a higher frequency of severe infections (p < 0.05), and invasive candidiasis was associated with allograft loss (p < 0.03). Annual survival rates of patients and allografts were 100% and 94%, respectively. The frequency of mild infections was higher than that observed in other studies using bacterial or viral prophylaxis. Nevertheless, the number of severe infections and the survival rates of patients and allografts were similar to those reported in previous studies.

[Diagnosis of a left-sided cervical aortic arch with nuclear magnetic resonance tomography]

Aortic arch anomalies are rare. They arise as a failure of the normal development of the left fourth dorsal arch. Cervical aortic arches are believed to result from persistence of the third dorsal arch, which re-routes the aortic arch in the cervical region. We describe a case of a left-sided cervical aortic arch in which the diagnosis was confirmed, and the anatomy defined, using magnetic resonance tomography.

A fatal case of cerebral artery gas embolism following fine needle biopsy of the lung

OBJECTIVES

To report a case of cerebral artery gas embolism (CAGE), following fine needle biopsy of the lung, and to discuss the pathophysiology and treatment.

CLINICAL FEATURES

A 65-year-old woman presented to an emergency department with the clinical features of a right thromboembolic stroke following a fine needle biopsy of the lung.

INTERVENTIONS AND OUTCOME

Computed tomography (CT) was performed after an unexpected deterioration in the woman's condition. The CT demonstrated the presence of intracranial translucencies consistent with CAGE. Hyperbaric oxygen therapy was initiated but, despite two courses, the woman's condition continued to deteriorate and she died two days later.

CONCLUSION

CAGE is a known but little appreciated complication of fine needle biopsy of the lung, and may be clinically indistinguishable from thromboembolic strokes. Successful treatment is dependent on early recognition and application of hyperbaric oxygen therapy, which appears to protect against injury and reverse many of the pathological changes associated with CAGE. The increasing popularity of fine needle biopsy of the lung as an outpatient procedure is likely to result in further presentations with CAGE to emergency departments.

Gamma delta T cells differentiate into a functional but nonproliferative state during a normal immune response

To obtain a homogeneous population of gamma delta T cells to investigate their role in an immune response, we have made a scid mouse doubly transgenic for rearranged gamma and delta genes. The receptor (KN6) encoded by these genes is specific for the major histocompatibility complex class I protein encoded by the T22b gene. This mouse contains high levels of transgenic gamma delta T cells in the spleen and thymus and no other T lymphocytes. Immunization of these KN6-scid (H-2d, TLd) mice with 10(7) C57BL/6J (abbreviated B6) (H-2b, TLb) spleen cells resulted in proliferation and activation of the gamma delta T cells in spleen and clearing of the allogeneic B6 lymphocytes. Subsequently, the majority of activated cells died by apoptosis and the remaining cells were anergic with regard to proliferation. The anergic cells did not respond to restimulation by B6 spleen cells in vitro or in vivo, and addition of exogenous interleukin 2 failed to restore the response to B6 cells. Cytotoxicity, a property of KN6+ cells during a primary stimulation, was no longer detectable in the proliferatively anergic cells. However, B6 spleen cells injected into mice primed 12 days previously were cleared with a much greater efficiency than on primary challenge and in an antigen-specific manner. We conclude that after exposure to antigen, gamma delta T cells rapidly proliferate into blasts; the majority of the blasts rapidly die, with the nonproliferating cells remaining in a highly active state for several weeks and able to initiate elimination of lymphoid cells bearing the TLb epitope.

Gamma/delta cells

Before TCR rearrangements, T cell progenitors are committed not only to the alpha beta and gamma delta T cell lineage but also to various subsets of both lineages. In the mouse, distinct gamma delta T cell subsets can develop in the fetal thymus, the adult thymus, or independently of a thymus, probably in intestinal epithelia. The two subsets that develop in the fetal thymus home to and are maintained throughout adult life in the skin and the mucosa of the uterus, vagina, and tongue. They are monospecific. This unusual restriction in receptor repertoires is the result of severe limitations in the generation of diversity in the fetal progenitors of these subsets and the thymic selection. After birth, one gamma delta T cell subset appears in the blood, spleen, and lymph nodes and one in the intestinal epithelia. The receptor repertoires of these subsets are characterized by the preferential usage of particular V gamma gene segments and extensive junctional diversity. Several murine and human gamma delta T cell clones have been shown to recognize classical MHC class I and class II proteins or MHC class I-like proteins, and in very few cases the presented peptides are known. We suspect that the various murine gamma delta T cell subsets interact with different antigen presenting cells which utilize different antigen presenting proteins and reside in different tissues. The function of gamma delta T cells remains unknown. Preliminary results of experiments with gene knock out mice which lack either alpha beta T cells or gamma delta T cells or both suggest that gamma delta T cells do not function as helper cells in humoral immune responses but may complement alpha beta T cells in the defense against various microorganisms.

Blockade of transgenic gamma delta T cell development in beta 2-microglobulin deficient mice

The gamma delta T cell receptor (TCR) of the hybridoma KN6 recognizes the self molecule encoded by a class I gene which maps within the TL region of the major histocompatibility complex (MHC) of H-2b mice. Mice transgenic (Tg) for this TCR were crossed with mice genetically deficient in beta 2-microglobulin (beta 2m). No mature Tg gamma delta T cells were detected in the thymus or the spleen of the beta 2m- gamma delta Tg mice. We conclude that interaction between the Tg gamma delta TCR and a beta 2m-associated molecule (probably an MHC class I molecule) is required for the generation of mature Tg gamma delta T cells.

Post- thymic in vivo expansion of mature alpha beta T cells

To discriminate whether peripheral T cell expansion is a property of pluripotent T cell precursors or of T lymphocytes precommitted to the expression of a single T cell receptor, we have evaluated the repopulation capacity of T lymphocytes expressing defined V beta gene products after transfer into syngeneic nude mice. The results showed no difference in the expansion potential of cells expressing different V beta s. The frequency of cells bearing different V beta gene products in the donor and the expanded cell populations are very similar, even when sorted populations enriched or deleted in T cells expressing a defined V beta gene product were used as a source of donor cells. These results demonstrate that peripheral T cells expressing alpha beta TCR are fully competent of extensive division in the peripheral pools.

Selective expansion of idiotype sharing T and B cells in cyclosporin A-mediated autoimmunity

CBA/N mice submitted to autologous bone marrow reconstitution after lethal irradiation and simultaneous Cyclosporin A (CsA) treatment develop a chronic graft-versus-host disease with autoimmune characteristics. When compared to normal controls, diseased mice show an overrepresentation of V beta 8-expressing T cells (65-80% of all CD3+ lymphocytes), together with a marked increase in the titres of serum Ig that specifically bind to F(ab')2 fragments of anti-V beta 8 F23.1 antibodies. Such 'V beta 8-like' Ig V regions are abundantly represented among the IgG2b and mAbs of an unselected collection of hybridomas derived from these mice. These mAbs are not multireactive Ig as they fail to bind to a panel of various antigens and antibodies, but often show simultaneous reactivity with anti-idiotypic mAbs to F23.1 and auto-binding. These molecules may provide the structural basis of V-region specific complementarities, driving the expansion of restricted T and B cell repertoires associated with pathological autoimmunity.

[Auto-immune polyglandular syndrome in an adult with chronic active hepatitis]

We present a case report with IgA deficiency, pernicious anemia, chronic active hepatitis, insulino-dependent diabetes mellitus and hypogonadism. A diagnosis of Polyglandular Auto-immune Syndrome was done and we discuss the difficulty in including this particular case in any of the types of the Neufeld's classification of Polyglandular Auto-immune Disease.

A monoclonal anti-idiotypic antibody against the antigen-combining site of anti-factor VIII autoantibodies defines and idiotope that is recognized by normal human polyspecific immunoglobulins for therapeutic use (IVIg)

The present study demonstrates that normal human immunoglobulins for therapeutic use (IVIg) contain anti-idiotypes that recognize an antigen-binding site-related idiotope of anti-Factor VIII autoantibodies defined by a mouse monoclonal antibody (MoAb). MoAb 20F2 was obtained by immunizing a mouse with affinity-purified anti-Factor VIII F(ab')2 fragments prepared from the IgG fraction of a patient with anti-Factor VIII autoantibodies. The monoclonal antibody was directed against an overlapping epitope on the antigen-binding site of the patient's anti-Factor VIII autoantibodies and the CH1 domain of human IgG1. The anti-Factor VIII activity of the patients's autoantibodies was neutralized by MoAb 20F2 in a dose-dependent manner. A fraction of the patient's anti-Factor VIII auto-antibodies was specifically retained on affinity columns of Sepharose-bound MoAb 20F2; anti-Factor VIII activity of antibodies in this fraction was totally inhibited by MoAb 20F2, indicating an idiotopic homogeneity of retained anti-Factor VIII autoantibodies. IVIg inhibited the anti-Factor VIII activity of 20F2 idiotope-positive F(ab')2 antibodies, thus indicating that the IVIg recognize the 20F2 idiotope on patient's autoantibodies. These observations further support the concept of the presence in IVIg of anti-idiotypes against autoantibodies associated with human autoimmune diseases.

I-E-linked control of spontaneous rheumatoid factor production in normal mice

The concentration of serum IgM molecules binding to IgG2a (rheumatoid factor [RF]) in solid phase assays is 10-100-fold higher in normal, unmanipulated C3H/HeJ (H-2k) than in C57BL/6 (H-2b) mice. Analysis of MHC-congenic mice with the prototype strains show that C3H SW (H-2b) are low, and B6.H-2k are high RF expressor strains, respectively. Furthermore, segregation of RF phenotypes in progenies from backcrosses to C3H/HeJ of (C3H/HeJ x C57BL/6)F1 hybrid mice shows MHC- and IgH-linked controls. RF phenotypes also segregate as if they are MHC linked in crosses between H-2-congenic strains (C3H/HeJ and C3H.SW). The study of intra-H-2 (k/b and k/s) recombinant mice suggested that RF phenotype control is linked to the I-E region. This was confirmed by the typing of C57BL/6 mice expressing a transgenic E alpha chain, and thus, I-E+, which, in contrast to nontransgenic littermates, are high expressors of RF.

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.

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.

Peripheral T lymphocytes: expansion potential and homeostatic regulation of pool sizes and CD4/CD8 ratios in vivo

Peripheral T lymphocytes are self-renewable cell populations since, when transferred into syngeneic T cell-deficient athymic mice, they expand in the absence of exogenous antigen stimulation. Quantification of the expansion potential of CD4+ cells by transfer of the same population into successive host mice shows that these cells are able to divide up to 56 times in vivo. Therefore, as a population, CD4+ cells can increase in size 8 x 10(5)-fold, an expansion potential of similar magnitude to that previously reported for colony-forming units. Injection of different numbers of T cells at different CD4/CD8 ratios is followed by T cell accumulation to a similar plateau in recipient nude mice. This indicates that peripheral T lymphocytes are tightly regulated by homeostatic mechanisms that control pool sizes and CD4/CD8 ratios, in a manner independent of the cell input into the peripheral compartment. This kinetic behavior of mature T cells permits the maintenance at the periphery of any T cell specificity previously selected in the thymus. The expansion capacity of peripheral T cells may also allow extensive modulation of peripheral T cell specificities, which would confer a major role to post-thymic selection of mature peripheral T cell repertoires.

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.

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.

Back-stimulation of B lymphocytes binding to helper T cell surface antigens

Helper T cells directed to B cell surface determinants activate their "targets" into polyclonal antibody production in vitro and in vivo, but B cells which bind to epitopes on the helper cell surface are preferentially induced. Furthermore, "anti-helper" B cell activation also occurs by "back-stimulation", that is even when the responding B lymphocytes are not specific targets for the inducing helper cells, as long as these are simultaneously activated by appropriate interactions with presenting cells. In our experimental systems, this is the only condition where "bystander" activation can be recorded. These findings suggest mechanisms of auto-antibody production associated with unrelated helper cell activity in vivo.

Most B cells in acute Trypanosoma cruzi infection lack parasite specificity

The specificity of B lymphocytes activated in the acute phase of murine Trypanosoma cruzi infection was analysed in a panel of immunoglobulin-secreting hybridomas derived by fusion of lymph node cells 7 days after intraperitoneal parasite inoculation. The immunoglobulin isotype distribution of the hybrids reflected the total plaque-forming cell (PFC) response in the animal at this point, with a predominance of IgG2a, IgM, and IgG2b. Screening of the hybridoma antibodies on parasite antigens by three independent methods (western blot, ELISA, and immunofluorescence) revealed only one (out of a total of 51) that bound a parasite molecule with an apparent molecular mass of 180 kDa. In contrast, antibodies of both IgM and IgG classes were found to react with a panel of autologous antigens. These results establish that most B cells activated by T. cruzi infection are not specific for parasite antigens and therefore indicate the relevance of analysing the totality of host responses to infection.

T cell dependence of the "natural" autoreactive B cell activation in the spleen of normal mice

A high frequency of clonal precursor B cells producing lytic antibodies to syngeneic erythrocytes treated with bromelain (BMRC) is revealed in normal mouse spleen cells by lipopolysaccharide-driven limiting dilution analysis. All such specificities are recovered as activated blasts after density gradient fractionation, the "small lymphocyte" pool being depleted of anti-BMRC reactivities. In contrast, the spleens of athymic (nude) mice contain undetectably low frequencies of these specificities in either lymphocyte compartment. Transfer of relatively low numbers of normal syngeneic splenic T lymphocytes to adult nude mice restores the high frequency of anti-BMRC clonal precursor B cells, again in the activated, but not in the resting spleen cell fractions. Large total T cells are more than tenfold better than resting T cells in reconstitution potential, as are enriched CD4+ as compared to CD8+ cells which are practically devoid of activity in this respect. These results apply exclusively to B cells at a differentiative stage that allows for extensive clonal expansion, since there is a marked difference between the frequency of clonal precursors determined by limiting dilution analysis and the frequency of Ig-secreting plaque-forming cells of the same specificity, and induced by the same mitogen in short-term cultures. The implications of these findings for the physiology of autoreactivity and repertoire selection in the compartment of perinatal B cells are discussed.

B cell participation in the recursive selection of T cell repertoires

Normal BALB/c mice produce 2,4,6-trinitrophenyl (TNP)-I-Ad specific T helper (Th) cells expressing a receptor heterodimer which share with anti-TNP antibodies an idiotope defined by the F6(51) anti-idiotypic antibody. Expression of this Th idiotype is controlled by major histocompatibility complex and immunoglobulin heavy chain-linked genes and results from antibody-dependent selection of T cell repertoires (Martinez-A. et al., Eur. J. Immunol. 1986. 16: 417). We now present evidence for the recursive nature of T----B cell repertoire selection and suggest that perinatal B cells, present in adult peritoneal cavity, operate in the early phases of this process. Thus, the Th idiotype is absent in BALB/c mice which are either suppressed from birth with anti-mu antibodies, or reconstituted with autologous bone marrow after lethal irradiation as adults. Supplementation of bone marrow reconstitution with syngeneic Thy-1-, Ly-1+ peritoneal B cells, however, selects Th cell repertoires that are undistinguishable from normal mice as to expression of the F6(51) clonotype. This effect is lost after depletion of Ly-1+ cells in the reconstituting Thy-1- peritoneal cell population. Interestingly, large in vivo "naturally" activated Ly-1- splenic B cells can also reconstitute Th idiotype expression if they are isolated from normal, but not from athymic, nude donors. However, transfer of normal large splenic T cells to adult nude mice "educates" the splenic "large B cell" compartment in these animals such that they acquire the ability to recursively select, upon transfer to bone marrow reconstituted recipients, the Th clonotype.(ABSTRACT TRUNCATED AT 250 WORDS)

A common idiotope on T cell receptors and antibodies expressed in the absence of network selection

The monoclonal antibody F6(51), directed to an idiotope of MOPC 460-like anti-1,4,6-trinitrophenl (TNP) antibodies produced in IgHa mouse strains, identifies in helper T cells from C57BL/6 (IgHb) mice with (4-hydroxy-3-nitrophenyl)acetyl (NP)-self specificity, a clonotypic determinant functionally and biochemically associated with the specific T cell receptor. The expression of this antibody-related T cell clonotype in C57BL/6 mice, although "recurrent", is independent of network selection, as shown by its presence in B mice suppressed from birth with anti-mu antibodies, and in IgH-congenic mouse strains. These results indicate aleatory cross-reactivity between T cell receptors and antibodies and command caution in network interpretations for "idiotype sharing".

Suppression of polyclonal antibody production in Trypanosoma cruzi-infected mice by treatment with anti-L3T4 antibodies

Acute Trypanosoma cruzi infection of mice results in a very marked polyclonal activation of B and T lymphocytes, accompanied by high numbers of Ig-secreting PFC and lectin-dependent effector CTL. Treatment of mice with monoclonal anti-L3T4 antibodies from the time of infection (days 0, 4, and 8) completely suppresses the polyclonal PFC response and CTL generation. Treatment of nude mice with antibody does not alter the lipopolysaccharide-induced polyclonal PFC response, and it only modulates the isotypic profile of the PFC response to T. cruzi infection, without reducing its magnitude. Furthermore, antibody-treated, T. cruzi-infected euthymic mice do not develop the typical B cell blastogenic response, but show high numbers of activated Lyt-2+ lymphoblasts in the spleen. These results indicate that effector cell generation in T. cruzi-infected mice is predominantly helper T cell-dependent.

Suppression of polyclonal antibody production in Trypanosoma cruzi-infected mice by treatment with anti-L3T4 antibodies

Acute Trypanosoma cruzi infection of mice results in a very marked polyclonal activation of B and T lymphocytes, accompanied by high numbers of Ig-secreting PFC and lectin-dependent effector CTL. Treatment of mice with monoclonal anti-L3T4 antibodies from the time of infection (days 0, 4, and 8) completely suppresses the polyclonal PFC response and CTL generation. Treatment of nude mice with antibody does not alter the lipopolysaccharide-induced polyclonal PFC response, and it only modulates the isotypic profile of the PFC response to T. cruzi infection, without reducing its magnitude. Furthermore, antibody-treated, T. cruzi-infected euthymic mice do not develop the typical B cell blastogenic response, but show high numbers of activated Lyt-2+ lymphoblasts in the spleen. These results indicate that effector cell generation in T. cruzi-infected mice is predominantly helper T cell-dependent.

"In vivo" activated splenic T cells are refractory to interleukin 2 growth "in vitro"

Naturally activated T lymphocytes present in normal mouse spleen were studied for direct reactivity to interleukin 2 (IL 2) and for binding of anti-IL 2 receptor (IL 2R) antibodies or radiolabeled IL 2. The majority of large-sized splenic T lymphocytes are IL 2R-; thus, at the most one third of large L3T4+ T cells and of large Lyt-2+ T lymphocytes bind (weakly) anti-IL 2R antibodies; furthermore, most IL 2R+ cells in the normal spleen are actually Lyt2-, L3T4-. Total large splenic lymphocytes do not express more than an average of 150 high-affinity IL 2R/cell. Such cell populations, as well as large T cells enriched from them, failed to proliferate exponentially in the presence of recombinant IL 2, but did not suppress the IL 2-dependent proliferative responses of small T cells activated in the same cultures. In vivo activation of small T cells, in concanavalin A-treated irradiated syngeneic hosts, also results in refractoriness to growth in recombinant IL 2. In addition, these cells remain insensitive to ligands such as concanavalin A, phorbol myristate acetate and ionomycin, in the presence or absence of IL 2. These results question the role of IL 2 as a growth factor of in vivo activated splenic T lymphocytes, or else indicate that most of these are terminally differentiated cells.

Turning (Ir gene) low responders into high responders by antibody manipulation of the developing immune system

The ability of helper T cells directed against trinitrophenyl-modified syngeneic spleen cells to recognize low-hapten densities on target cells is under major histocompatibility complex-linked Ir gene control. Thus, BALB/c (H-2d) mice are low responders while H-2 congenic BALB.C3H (H-2k) mice are high responders. Immunization of adult BALB/c mice with the monoclonal antibody F6(51), directed to shared idiotopes by anti-trinitrophenyl antibodies and clonal receptors on anti-trinitrophenyl-self helper T cells, leads to the production of high titers of circulating idiotype, has no influence on helper T cell idiotypic profiles, but shifts to a high-responder phenotype the ability of helper T cells to recognize low-hapten densities. These effects on Ir gene phenotype are even more striking in untreated progenies from F6(51)-immunized BALB/c females, which are better responders than genetically high-responder BALB.C3H mice, although completely different in the expression of the F6(51)-defined clonotype. The general significance of these findings on Ir gene-directed T-cell repertoire selection is discussed, for they constitute formal evidence against antigen-presentation as a mechanism of Ir gene effects and strong support for the importance of maternal influences on the development of T-cell repertoires.

A functional idiotypic network of T helper cells and antibodies, limited to the compartment of "naturally" activated lymphocytes in normal mice

As shown previously, idiotype (Id) sharing between anti-2,4,6-trinitrophenyl T helper (Th) cells and antibodies in BALB/c mice results from immunoglobulin (Ig)-dependent selection of the T cell repertoire. In contrast, a clonotype defined by the same F6(51) anti-Id antibody is expressed by C57BL/6 anti-(4-hydroxy-3-nitrophenyl)acetyl Th cells independently of Ig influences. We have now used these systems to test the hypothesis that Ig-dependent Th cell repertoire selection occurs in the compartment of "naturally" activated lymphocytes. "Naturally" activated or resting splenic L3T4+ cells were separated from normal BALB/c and C57BL/6 mice and tested, either directly or after in vitro priming, in hapten-specific helper assays for expression of the clonotope defined by the F6(51) anti-Id antibody. The results show the selective expression of the antibody-dependent T cell Id in the "naturally" activated helper cell compartment. In contrast, when the T cell Id is expressed in the absence of Ig-dependent selection, it is only detected in the resting helper cell repertoire. Furthermore, BALB/c "natural" IgM antibodies with anti-Id specificities similar to F6(51) show functionally relevant interactions with syngeneic "naturally" activated Th cells. These are also characterized by high paratopic/Id degeneracy, as compared to helper cells obtained by conventional immunization. These results demonstrate repertoire differences between the set of (resting) lymphocytes participating in immune responses, vs. those "internally" activated in normal individuals. They also suggest the importance of Id network interactions in the compartment of "naturally" activated T and B cells.

Autonomous activation of B and T cells in antigen-free mice

The spleen of adult antigen-free mice contains a sizable proportion (5-15%) of activated cells in all lymphocyte sets, as marked by the membrane expression of immunoglobulins, L3T4 and Lyt-2 antigens. The frequency of activated cells is very high in early post-natal life, and reaches adult levels by 6 weeks of age when it is comparable to that observed in healthy unmanipulated mice raised in conventional conditions. The effector B cell compartment is quantitatively similar in antigen-free mice and specific pathogen-free mice, but the former is deficient in isotype diversification, since IgG- and IgA-secreting cells are drastically reduced. The effector T cell compartment is slightly reduced in number, but is equally competent in providing help or suppression of syngeneic B cells. The results indicate the existence of a compartment of the immune system displaying autonomous self-determined activity which is predominant early in life. This compartment, physically localized to the spleen, appears to be distinct from an antigen-dependent compartment which is essential for the development of peripheral lymphoid organs draining sites of "natural" environmental immunization.

The role of immunoglobulin receptors in "cognate" T-B cell collaboration

The functional effects of anti-Ig antibodies have been investigated, using an experimental system where B cell activation is brought about by direct and specific interactions with T helper (Th) cells without participation of surface Ig receptors on the responding B cell. We have used Th cell lines and clones directed to class II major histocompatibility complex antigens of the responding B cells, and titrated into cooperative cultures either purified rabbit anti-mouse mu, or monoclonal mouse anti-delta antibodies. Both types of antibodies greatly enhanced B lymphocyte responses to suboptimal concentrations of functionally efficient Th cells, while they had no effect in cultures containing optimal Th:B cell ratios. In contrast, helper activity by low efficiency Th was, at all Th:B cell ratios, enhanced by appropriate concentrations of anti-Ig antibodies. Anti-Ig effects were exclusively observed when B cells were the targets for "cognate" recognition by Th cells. We conclude that ligand binding to surface Ig receptors on resting B cells fails, in our experimental conditions, to overcome "linked" collaboration, but it greatly facilitates productive Th-B cell interactions. Whatever the mechanisms underlying this facilitation, the observations imply roles of surface Ig in Th-dependent B lymphocyte activation other than either passive "focusing" of antigen or activation into reactivity to soluble, unspecific factors.

The basis for major histocompatibility complex (MHC) and immunoglobulin gene control of helper T cell idiotopes

BALB/c helper T cells, prepared against 2,4,6-trinitrophenyl (TNP)-derivatized syngeneic spleen cells, fail to recognize other hapten modifications [(4-hydroxy-3-nitrophenyl)acetyl, fluorescein isothiocyanate] of syngeneic cells, as well as TNP-derivatized cells from major histocompatibility complex-congenic donors. T helper cell interactions with "presenting" cells and "target" B lymphocytes are inhibited by monoclonal antibodies directed either to the hapten or to I-A molecules on target cells. Helper activity is also inhibited by monoclonal anti-idiotypic antibodies directed to an idiotope expressed by the TNP-binding myeloma protein MOPC460, but not by soluble TNP-protein conjugates. The study of congenic mouse strains revealed that while the fine specificity of TNP recognition and the quantitative levels of M 460 idiotope expression are I-A linked, the expression of the M 460 idiotope by helper cells is controlled by IgCh-linked genes. Absence of anti-idiotope inhibition of helper cells prepared in anti-mu-suppressed mice suggests, however, that immunoglobulin idiotype expression by T cells results from network interactions selecting available lymphocyte repertoires which operate before antigenic stimulation.