IgG anti-F(ab')2 antibodies from SLE patients react with immunodominant residues in kappa CDRs, but show reduced C kappa region reactivity

We studied reactivity of affinity-purified human IgG anti-F(ab')2 antibodies for antigenic determinants on kappa light chains. Variable (VL) and constant (CL) regions of a human kappa I light chain (EU) were studied for enzyme-linked immunosorbent assay reactivity with monoclonal anti-k antibodies and human IgG antiF(ab')2 using overlapping heptamers of primary sequence synthesized as peptides on polypropylene pins. Polyclonal IgG anti-F(ab')2 antibodies isolated by affinity chromatography from the serum of patients with systemic lupus erythematosus (SLE) were found to react primarily with CDR1- and CDR3-related peptides. The most reactive residues included IL29, TRY32, LEU33, ALA34, GLU90, TYR91, and ASN 92. No striking difference in overall V-region anti-F(ab')2 reactivity profiles was noted when 10 IgG anti-F(ab')2 preparations from normal subjects and SLE patients were compared. In contrast, however, when tested against overlapping C kappa heptamer sequences, the reactivity in SLE-associated anti-F(ab')2 antibodies was markedly decreased. We report that this difference may reflect a defect in anti-idiotypic control mechanisms in SLE.

Molecular localization of human IgG anti-F(ab')2 reactivity with variable- and constant-region lambda light-chain epitopes

Human IgG antibodies reacting with antigenic determinants on F(ab')2 fragments represent generic antiidiotypic antibodies present in the serum of normal individuals. Additionally, the titers of these antibodies in the sera of patients with systemic lupus erythematosus (SLE) are inversely related to disease activity. Because these autoantibodies recognize predominantly light chain-related epitopes, especially lambda type, we synthesized constant (C)lambda- and variable (V)lambda-related overlapping 7-mer peptides on polypropylene pins to determine anti-F(ab')2-reactive epitopes on human lambda light chains. ELISA reactivity of affinity-purified anti-F(ab')2 antibodies obtained from normal individuals and from patients with SLE, as well as murine anti-human light-chain monoclonal antibodies specific for C lambda and V lambda subgroup-related determinants, was tested using the overlapping 7-mers of human lambda light-chain sequence. The patterns of reactivity against C lambda-related peptides were similar in both normal and SLE-derived anti-F(ab')2 antibodies. However, reactivity profiles against V lambda-related peptides were distinctively different between the normal and the SLE-associated anti-F(ab')2 autoantibodies. A decrease in reactivity among the SLE IgG anti-F(ab')2 antibodies was noted for particular amino acid V lambda complementarity-determining region (CDR) residues, including glycine at positions 27 and 54, alanine at 16 and 37, and tyrosine at 28 and 91. This different pattern of reactivity from normal may indicate that in SLE there is a failure of antiidiotypic control mechanisms, as reflected by a defect in production of antibody to immunodominant V lambda CDR residues.

CDR molecular localization of possible anti-idiotypic anti-DNA antibodies in normal subjects, patients with SLE, and SLE first-degree relatives

Patients with active systemic lupus erythematosus (SLE) with disease worsening or severe flares frequently show very low levels of serum immunoglobulin G (IgG) anti-F(ab')2 antibody. Anti-F(ab')2 antibody probably represents a polyclonal collection of generic anti-idiotypic antibodies involved in immune homeostasis. We synthesized the entire variable regions of the heavy and light chains (VH and VL) of two monoclonal anti-DNA antibodies, V88 and 2A4, as overlapping 7-mers on small polypropylene pins and tested these linear segments of anti-DNA V-regions for reactivity against serum samples from 10 normal subjects with high serum IgG anti-F(ab')2, 11 normal subjects with low anti-F(ab')2, 5 patients with SLE with active uncontrolled disease, 3 patients with SLE in remission, and 8 unaffected normal first-degree SLE relatives. VH and VL regions of a human monoclonal IgG anti-rabies antibody were also tested as a control. Concordant IgG antibody reacting with the same complementarity-determining regions (CDRs) was arbitrarily scored as indicative of the presence of anti-idiotypic antibody in test serum samples. Among normal subjects with either high or low serum anti-F(ab')2 levels, 10% to 21% showed strong concordant anti-CDR reactions with either the monoclonal anti-DNA or the control monoclonal anti-rabies V-region sequences. However, all patients with active SLE showed no detectable anti-CDR-reactive antibody. Patients with SLE in remission often showed return of strong concordant anti-CDR antibody. Normal unaffected SLE relatives also showed high levels of anti-CDR reactivity for both monoclonal anti-DNA and anti-rabies antibody sequences.

Active systemic lupus erythematosus is associated with depletion of the natural generic anti-idiotype (anti-F(ab')2) system

OBJECTIVE

To study the relationship of serum IgG anti-F(ab')2 and clinical disease activity in 108 patients with systemic lupus erythematosus (SLE) and to determine whether low serum anti-F(ab')2 with active renal disease is accompanied by deposition of anti-F(ab')2 in renal immune complex lesions.

METHODS

We studied 108 patients with definite SLE over a 5 yr period and assayed serum anti-F(ab')2 levels in relation to degree of clinical disease activity. Renal biopsy eluates of 26 patients with SLE were examined by enzyme linked immunosorbent assay (ELISA) for relative amounts of IgG, anti-DNA, and IgG anti-F(ab')2.

RESULTS

Active SLE was strongly associated with low serum anti-F(ab')2. SLE renal biopsy eluates frequently contained high levels of IgG and IgG anti-DNA and lower, but definite, IgG anti-F(ab')2 activity. When specific activity of IgG anti-DNA and IgG anti-F(ab')2 was compared between kidney biopsy eluates and concomitant serum, marked relative renal concentration was found for both anti-DNA (19-fold) and anti-F(ab')2 (74-fold). Some biopsy eluates contained IgG antibodies bearing apparent double specificity for both DNA and F(ab')2.

CONCLUSION

Active SLE is often associated with low serum anti-F(ab')2. Relative enrichment over specific activity in serum of both IgG anti-F(ab')2 and anti-DNA in SLE kidney biopsy eluates may indicate participation of both reactants in the glomerular disease process. Low serum anti-F(ab')2 in active SLE may reflect down modulation of failure of idiotypic control mechanisms associated with disease progression.

Autoreactivity in HIV-1 infection: the role of molecular mimicry

Autoimmunity during HIV-1 infection may contribute to the immunopathogenesis of AIDS. Titers of autoantibodies to HLA molecules and other surface markers of CD4+ T cells appear to increase with the progression of disease and may correlate with lymphopenia. Other autoantibodies are directed at a number of regulatory molecules of the immune system. Genesis of autoreactivity may be related to structural homologies of HIV-1 env-products to such functional molecules involved in the control of self-tolerance. The most impressive similarities include the HLA-DR4 and DR2, the variable regions of TCR alpha-, beta-, and gamma-chain, the Fas protein, and several functional domains of IgG and IgA. Thus, HIV-1 infection may induce dysregulation leading to autoimmune response, through a number of molecular mimicry mechanisms. Pathogenicity of antibodies to T cells could also include the activation of membrane-to-nucleus signal transducers resulting in increased apoptosis. The evolution of autoimmune mechanisms during HIV-1 infection cannot exclude, however, progression to immunoproliferative malignancy, since aspects of oligoclonal immune response to HIV-1 components may occur in several autoimmune diseases which in some instances evolve to lymphoma.

Long-term therapy with recombinant human erythropoietin (rHu-EPO) in progressing multiple myeloma

Recombinant human erythropoietin (rHu-EPO) is an effective growth factor for erythroid progenitor cells in anemia provoked by several conditions, including bone marrow tumors such as multiple myeloma (MM). We studied a group of 54 patients with MM undergoing second-induction chemotherapy. Thirty of them were randomly assigned to receive rHu-EPO at an initial dosage of 150 units/kg body weight three times a week, increased to 300 units/kg from the sixth week to the end of the 24-week study. Hemoglobin (Hb) levels increased in 77.7% of these patients by the eighth week. In addition, five transfusion-dependent patients in treatment with the VMCP protocol completed the trial without requiring blood supplement after the third month, whereas seven control patients required frequent supplements. Monthly assessment of hematologic parameters demonstrated the ability of rHu-EPO to increase reticulocyte counts, whereas five patients became resistant to the second-induction chemotherapy in apparent concurrence with their rHu-EPO therapy. The response to rHu-EPO in four of the five MM patients receiving cytotoxic protocols combined with alpha-interferon (alpha-IFN) included an increase of serum IgM after the third month. This effect was not demonstrable in any other group, including three rHu-EPO-untreated patients undergoing alpha-IFN + VMCP combined therapy, as well as rHu-EPO-treated patients not receiving alpha-IFN. Our data suggest that alpha-IFN plus rHu-EPO treatment in MM patients is effective in restoring normal B cell function. These results may reflect in vivo the modulation of normal human B cells and lymphoblasts by rHu-EPO observed in vitro.

Immunomodulation of T and B cell functions in multiple myeloma patients treated with combined erythropoietin and alpha-interferon therapy

T and B lymphocyte functions were investigated in the course of a long-term trial of recombinant human erythropoietin in patients with progressing multiple myeloma. Peripheral mononuclear cell as well as T and B lymphocyte cultures were established at the 1st, 13th, and last week of the 24-week protocol from 16 treated and 15 untreated patients. Control cultures from healthy individuals were also obtained. A suppression of phytohemagglutinin-induced proliferation of T cells was noted in all 1st-week cultures, whereas a variable increase of 3H-thymidine uptake was noted at the end of the trial in the cultures from erythropoietin-treated patients. A significant increase was observed, however, in cultures from 5 erythropoietin-treated patients who also received alpha-interferon when their cells were grown in the presence of the hormone. In contrast, the pokeweed mitogen-driven in vitro synthesis of immunoglobulins was not significantly influenced by the duration of erythropoietin treatment, nor by addition of the hormone. IgG secretion by Epstein-Barr virus-transformed B cells in cultures from 9 erythropoietin-treated and 6 untreated patients was enhanced in the presence of both recombinant human erythropoietin and alpha-interferon. These data suggest that synergy between the two cytokines may variably modulate certain immune functions in vitro. This effect might account for the increase of serum IgM levels noted in some patients who received alpha-interferon.

[Apoptosis or programmed cell death: regulatory and pathophysiological mechanisms]

Apoptosis is an active death process genetically encoded to eliminate abnormal or unwanted cells. The phenomenon is induced by a cascade of molecular events leading to nucleolysis by endonucleases and involves a number of membrane receptors and cytoplasmic proteins. These structures (including Fas, müllerian inhibiting substance, p53 and the c-myc oncogene) contribute, by interactive regulatory mechanisms, to the promotion or inhibition of apoptosis, on the basis of both external stimulus and cell activation state. Since apoptosis is a selective process to suppress defective cells, deregulation of genes encoding for such apoptosis-related proteins could be relevant in the growth of several tumors. Remarkably, overexpression of the bcl-2 gene in a few experimental lymphomas has been associated with neoplastic proliferation because of its inhibitory effect on apoptosis. Conversely, early activation of Fas, an apoptosis-inducing gene on HIV-infected CD4+ lymphocytes, is thought to aggravate T cell lymphopenia in HIV infection by increasing the level of normal apoptosis. Genetic deregulation of apoptosis has also been postulated in the pathogenesis of several diseases. Indeed, while preliminary studies suggest that apoptosis plays a role in autoimmune disorders including systemic lupus erythematosus, the pathogenesis of a few degenerative neuropathies, such as Alzheimer's disease, could depend on a similar altered mechanism in apoptosis of neuronal cells. However, no studies are presently available to suggest that exploitation of molecular events of apoptosis would imply therapeutic progress.

Distribution and antigenic analysis of circulating F(ab')2-reactive IgG in patients with HIV-1 infection

Serum titers and molecular specificity of anti-F(ab')2 antibodies were investigated in human immunodeficiency virus type 1 (HIV-1) infection with respect to their supposed cytopenic role on CD4+ cells. The levels of antibodies to F(ab')2 fragment and to HIV-1 glycoprotein epitopes were measured by immunoenzymatic methods in an HIV-1+ population, including 86 drug addicts, 12 sexually infected patients, and 1 hemophiliac, grouped into Walter Reed (WR) clinical stages 2 to 6 of HIV-1 infection. Monoclonal F(ab')2-reactive IgM and IgG from cloned Epstein-Barr B cell transformants of selected patients were also investigated in regards to their HIV-1 glycoprotein specificities and cytotoxicity to the CD4+ cell membrane antigens (CEM) lymphoblasts by a Terasaki assay. Group A (51 sera from WR2 patients) showed the highest titers of IgG anti-F(ab')2 with no correlation to positivities to gp120, whereas sera with undetectable anti-F(ab')2 levels from group B (37 WR5 and WR6 patients) and from group C (11 WR3-WR6 patients with lymphocytotoxin-associated lymphopenia) were reactive to the virus envelope. Both anti-F(ab')2 monoclonal IgM and IgG failed to cross-react with the HIV-1 glycoproteins and the CD4+ CEM. Based on our data, anti-F(ab')2 antibodies are apparently unrelated to the CD4+ lymphopenia occurring in HIV-1-infection. In addition, their inability to bind the HIV-1 gp120 as sequence homologue of the CH1 domain of IgG suggests that their molecular target could include a few epitopes located within the VH and VL regions, thus supporting their potential role of antiidiotype molecules as described in autoimmunity.

Expression of F4, 8.12, 3I, and 16/6 anti-DNA idiotype-related antigens on cationic human IgG myeloma proteins

One hundred cationic isolated human IgG myeloma proteins were studied for expression of four anti-DNA idiotypic (Id) markers F4, 3I, 8.12, and 16/6. Forty-three of 100 myelomas showed the presence of at least one anti-DNA idiotype. Twenty-seven were F4 positive, 18 were 16/6 positive, 8 were 3I positive, and 7 were positive for 8.12. Two different anti-DNA idiotypic markers were found together on the same 14 myeloma proteins and 3 myelomas showed three different anti-DNA Ids. Anti-DNA activity was found on only 1 of 100 myelomas but not associated with presence of an anti-DNA Id. Ten myelomas showed anti-F(ab')2 activity and 6 of these also showed the presence of an anti-DNA Id marker. When myeloma proteins expressing anti-DNA Ids were compared in direct competition ELISAs with known Id-positive human IgG anti-DNA antibodies, much less inhibition was recorded in comparison to known human anti-DNA antibodies. Our findings indicate that human IgG myeloma proteins may show positive reactions with anti-DNA idiotypic antibodies but do not express the complete anti-DNA idiotypic antigenic complex.

Differential expression of two ICAM-1 epitopes and LFA-1 chains in B-cell non-Hodgkin's lymphomas

B-cell non-Hodgkin's lymphomas (B-NHL) and B-cell areas of reactive lymphadenopathies were investigated immunohistochemically for expression of two distinct ICAM-1 epitopes, Me14/D12 and P3-58, and the LFA-1 alpha and beta chains. Partial or total loss of expression of one or both epitope(s) and/or chain(s) was evident in all B-NHL in function of increasing Working Formulation (WF) malignancy grade, with most defects in the high-grade tumors, namely the lowest detectability of the ICAM-1 Me14/D12 and LFA-1 alpha chain, the lowest co-expression of ICAM-1 epitopes and LFA-1 chains, and the most frequent simultaneous loss. The ICAM-1 and LFA-1 profiles overlapped within the low- and intermediate-grades, whereas striking differences between the high-grade subtypes were detected. Specifically, Burkitt's and lymphoblastic tumors always lost both epitopes and both chains. Large cell, immunoblastic tumors occasionally did so, and also showed either uncoordinated expression or co-expression of these constituents. It is suggested that expression defects of this type may help differentiate malignant from benign lymphoproliferations, and also be involved in the progression of B-NHL, since most are observed in high-grade tumors, whose ICAM-1 and LFA-1 profiles indicate that their subtypes are the expression of distinct normal B-cell differentiation stages.

Bone marrow angiogenesis and progression in multiple myeloma

Tumour growth is angiogenesis-dependent. We found a high correlation between the extent of bone marrow angiogenesis, evaluated as microvessel area, and the proliferating (S-phase) fraction of marrow plasma cells, evaluated as labelling index (LI), in patients with multiple myeloma (MM) and in those with monoclonal gammopathies of undetermined significance (MGUS). Angiogenesis itself was significantly associated with active as opposed to non-active MM and MGUS. The highest microvessel area accompanied rapidly progressive MM with the highest LI. When a cut-off value of 2% or greater of the microvessel area was used, most patients with active MM were classified correctly. The risk of active disease in patients with MM increased in parallel with the microvessel area. A causal relationship between plasma cell growth, activity phase in MM and marrow angiogenesis is suggested. Since angiogenesis proceeds in step with the enlargement of plasma cell tumours and the activity phase in MM, its measurement could be a useful prognostic marker in patients with plasma cell proliferative disorders.

Pathogenic anti-DNA idiotype-reactive IgG in intravenous immunoglobulin preparations

This study was addressed to explore the reactivity of natural anti-idiotypes from commercial lots of immunoglobulins to several idiotypes (Ids), usually expressed by anti-DNA molecules in lupus nephritis. Eleven intravenous immunoglobulin (IVIG) preparations and nine (three polyvalent and six hyper-immune) intramuscular IgG were investigated for specific content of anti-DNA, anti-F(ab')2 and antibodies reacting with several anti-DNA IgG Ids. Two samples (nos 6 and 11) showed high reactivity with allogeneic F(ab')2 and with F(ab')2 of myeloma proteins bearing the anti-DNA Id 3I+ and the 8.12+. Since both 3I and 8.12 Id markers are known to characterize pathogenic anti-DNA IgG in systemic lupus erythematosus (SLE), anti-Id antibodies to these markers were obtained by absorbing the IVIG samples nos 6 and 11 to Sepharose columns coupled with pooled F(ab')2 fragments of 3I(+)-F4(+)-8.12(+)-myeloma proteins. Inhibition experiments showed that anti-8.12 Id-eluted IgG induced a selective suppression of the DNA-reactive antibodies derived from patients with active lupus nephritis to their substrate, suggesting the involvement of 8.12+ molecules in the SLE glomerular damage. Since 8.12+ anti-DNA are nephritogenic antibodies, the occurrence of anti-8.12+ Id in commercial IVIG may be of potential therapeutic relevance in modulating the pathogenic SLE Id network. Previous variable results of IVIG treatment in SLE, such as resolution of proteinuria or worsening nephritis, could be related to variable enrichment of different lots of IVIG in suppressive anti-pathogenic Id antibodies.

Molecular specificities of CD4+ T cell-reactive IgM in human immunodeficiency virus (HIV-1) infection

The molecular targets and biological properties of lymphocytotoxic sera in 11 human immunodeficiency virus (HIV)+ subjects in CDC stages II to IVC were investigated. A purified soluble CEM membrane used as the CD4+ T cell clonotypic model in immunoblotting techniques revealed a homogeneous pattern of IgM-mediated reactivity to a 43.5-kDa membrane component in 10 sera. Conversely, CEM membrane-reactive IgG from these sera were weakly reactive to various antigens with no prevalent specificity. ELISA assay against purified 25.5-, 43.5-, and 60.8-kDa CEM membrane antigens revealed a significant affinity of IgM from sera 3, 8, 9, and 10 for the 43.5-kDa receptor, thus confirming the high specificity of these cytotoxic antibodies for their substrate. Additional experiments included the idiotypic saturation of purified IgM molecules with increasing amounts of the 43.5-kDa antigen. Functional inhibition of CEM-reactive IgM by their antigen was dose-dependent. The maximum inhibition of the ELISA reactivity was detected at 1/7 antigen/antibody concentration. By contrast, a significant decline of cytotoxic properties of sera 8, 9, and 10 to CEM lymphoblasts was noted only when equivalent concentrations of the 43.5-kDa receptor and purified IgM were incubated. In addition, the 43.5-kDa antigen appeared to be the preferential target of cytotoxic IgM in HIV-1 infection, since purified cytotoxic IgM from two SLE patients were not inhibited by this molecule. Our data provide specific molecular support for earlier evidence of exacerbation by T cell-reactive antibodies of the lymphopenia associated with HIV-1 infection.

Human anti-F(ab')2 antibodies show preferential reactivity for F(ab')2 molecules bearing lambda light chains

In order to evaluate binding specificities of anti-F(ab')2 antibodies from patients with systemic lupus erythematosus (SLE) and from normal healthy controls, F(ab')2 fragments were prepared from 24 IgG myelomas with defined isoelectric points, DNA-associated idiotypes, and kappa/lambda light chain types. Using ELISA and hemagglutination assays, anti-F(ab')2 antibodies from 12 healthy controls and 29 SLE patients were observed to exhibit preferential binding (lambda > kappa) to myeloma F(ab')2 fragments composed of lambda light chains (P < 0.0001). No correlation of anti-F(ab')2 binding and presence of cationic, neutral, or anionic isoelectric points or for DNA-associated idiotypes on monoclonal F(ab')2 was detected. Anti-F(ab')2 antibodies, often elevated in SLE during remission, show preferential specificity for F(ab')2 fragments bearing lambda light chains.

Differential isotype expression and binding properties of T cell-reactive antibodies in human immunodeficiency virus (HIV) infection

Isotype and binding characteristics of T cell-reactive antilymphocyte antibodies (ALA) were investigated in 287 human immunodeficiency virus (HIV)+ sera from patients with CDC II to IVC clinical disease. Using purified soluble T-lymphoblast (CEM cell line) membranes and an ELISA method, 29 HIV+ sera showed significant reactions with this substrate and a selective expression of IgG-ALA was detected in 7 HIV+ sera. Subsequent microcytotoxicity assays, utilizing peripheral T lymphocytes and CEM cells as targets, demonstrated no significant cytotoxic capability in such sera, whereas 12 of 17 HIV+ serum samples with IgM-ALA ELISA reactivities showed a significant degree of killing in the Terasaki test. Further experiments of saturation of CD4 molecules on CEM extract by OKT4 monoclonal antibody (MoAb) induced a high inhibition of IgG-ALA binding to the T-cell membranes in only two IgG-ALA+ sera (No. 93, CDC III; No. 179, CDC II stage). Conversely, treatment of CEM membrane lysate with Leu3a MoAb, specific for the gp120 reactive domain of the HIV receptor, failed to prevent membrane binding in all seven of the IgG-ALA+ sera. Following the adsorption of serum 93 on a T-cell membrane antigen affinity column, SDS-PAGE analysis demonstrated that the predominant ALA material reacting with T-cell membranes was IgG with no detectable traces of IgM. These data provide evidence that ALA in HIV+ patients may be simultaneously or selectively expressed as IgG and/or IgM with different properties.(ABSTRACT TRUNCATED AT 250 WORDS)

Parallelism of serum anti-F(ab')2 and anti-cationic IgG reactivities in patients with systemic lupus erythematosus

Cationic anti-DNA antibodies may be related to glomerular injury in murine lupus nephritis or in patients with systemic lupus erythematosus (SLE). Therefore, anti-cationic antibodies in SLE could include antibodies with regulatory function on such pathogenic cationic molecules. Since anti-F(ab')2 antibodies may be involved in the idiotype control of anti-DNA antibodies in some patients with inactive SLE, the present study was aimed to determine if SLE patients with significant serum levels of anti-F(ab')2 produce antibodies reacting with cationic IgG molecules. Three SLE sera with high titers of anti-F(ab')2 antibodies were individually adsorbed by sequential affinity chromatography on three Sepharose columns coupling normal IgG from Cohn Fraction II, pooled cationic IgG myeloma paraproteins displaying idiotypic anti-DNA markers (F4 and 8.12), and F(ab')2 fragment from allogeneic IgG, respectively. Eluates obtained from cationic IgG adsorption showed predominant anti-F(ab')2 reactivity. A similar profile was also detected in a serum from a normal control donor with high levels of anti-F(ab')2. Biotinylation of anti-cationic eluates showed that such antibodies were significantly more reactive with cationic than anionic or neutral IgG, confirming their apparent affinity for positively charged antigens on IgG molecules. Since anti-cationic absorptions were able to remove the anti-F(ab')2 activities in the SLE sera studied, it is possible that anti-cationic antibodies could function as immunoregulatory antibodies in the idiotypic control of some SLE autoreactive phenomena, including glomerular anti-DNA deposition.

Monoclonal antibodies against human anti-F(ab')2 antibodies react with light chain epitopes

Anti-F(ab')2 antibodies affinity isolated from sera of patients with rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), or normal SLE relatives were used to produce monoclonal antibodies (mAbs) in Balb/c and NZB mice. Four of five mAbs showed only primary light chain specificity. Only one mAb produced in an NZB mouse against anti-F(ab')2 from a single SLE patient showed anti-mu-chain specificity. Parallel identical control immunizations with IgG or a single human IgG kappa myeloma produced mAbs with a predominant gamma-chain/Fc fragment specificity. Anti-light chain specificity of mAbs was demonstrated to involve epitopes requiring tertiary structure of the entire light chain instead of antigens confined to Ckappa/lambda or Vkappa/lambda fragments. Anti-kappa specificity of three mAbs was extremely similar but not identical to that defined by anti-Km1 allotyping systems. No evidence was obtained with any of the mAbs produced for antigens unique to SLE or RA anti-F(ab')2 antibodies. The light chain antigenic prominence of many anti-F(ab')2 antibodies may reflect structural features shared by this group of immunoglobulins somehow important for their biologic function.

Isotype, distribution and target analysis of lymphocyte reactive antibodies in patients with human immunodeficiency virus infection

Anti-lymphocyte (ALA) antibodies were investigated by using both microcytotoxicity and immunofluorescence analyses in 87 subjects with different clinical features of human immunodeficiency virus (HIV) infection. A similar mean percentage of killing in microcytotoxicity assays using heterologous lymphocytes as cellular target was recorded in four groups of patients, including 36 HIV-seropositive asymptomatic subjects, 34 patients with HIV-induced lymphadenopathy syndrome (LAS), 13 with acquired immunodeficiency syndrome (AIDS)-related complex (ARC), and 4 patients with the full-blown AIDS. Conversely, an increasing percentage of ALA-positive subjects paralleled the evolution of the HIV infection. The majority of ALA were IgM isotype with a significant reactivity against T cells. This specificity was indifferently directed to CD3+, CD4+, and CD8+ lymphocytes. In additional experiments employing enzymatic digestion of lymphocyte membrane antigens, we demonstrated that CD4 and CD8 receptors were digested by the pronase, whereas CD3 molecules were highly resistant. Subsequent flow cytometry analyses using these pronase-digested T cells showed that reactivity of ALA for their target was unchanged. Our data suggest that antigenic specificities of ALA in HIV infection are resistant to pronase treatment and are not related to CD4 and CD8 molecules.

Distribution of anti-F(ab')2 antibodies and the 16/6 idiotype in systemic lupus erythematosus (SLE) probands and kindreds

Levels of serum anti-F(ab')2 antibodies and expression of the 16/6 anti-DNA idiotype were studied in 103 sera from first-degree relatives of 17 systemic lupus erythematosus (SLE) kindreds. Among healthy SLE relatives, 35.9% showed anti-F(ab')2 elevations and 24%, Id 16/6 expression. Forty-three and two-tenths percent of healthy SLE relatives with elevated anti-F(ab')2 also showed expression of 16/6; when Id 16/6 was positive, 16 of 25 relatives (64%) showed parallel elevations of anti-F(ab')2. However, within individual families, distribution patterns of elevated anti-F(ab')2 and Id 16/6 often did not coincide. Affinity-isolated anti-F(ab')2 from four members of a single SLE kindred showed relative enrichment for Id 16/6 in only two of the four individuals studied. Moreover, none of the isolated anti-F(ab')2 antibodies within this kindred or another kindred showing 16/6 Id expression reacted directly with 16/6 Id. Our studies suggest that whereas both anti-F(ab')2 and Id 16/6 are increased within SLE kindreds, expression of the two does not always coincide. Furthermore, anti-F(ab')2 antibodies do not show direct reactivity with Id 16/6. A number of anti-DNA idiotypic markers may play a role in idiotypic networks among such SLE kindreds.

Studies of anti-F(ab')2 antibodies and VH region distribution among SLE kindreds

Genomic DNA samples from kindreds of patients with systemic lupus erythematosus were examined for VH region genotypes using probes representing JH and representative members of the human VH gene families (VHI-VHVI) in parallel with distribution of high levels of anti-F(ab')2 (generic anti-idiotype) in some non-affected SLE family members. Identical VH region genotypes were present in an SLE female proband and one unaffected normal male sibling. Three normal unaffected family members with elevated anti-F(ab')2 showed AB, AD, and AC (non-identical)VH genotypes. VH region genotype pattern distributions do not appear to directly correlate with production of high levels of anti-F(ab')2 in SLE families.

Immunologic effects of long-term thymopentin treatment in patients with HIV-induced lymphadenopathy syndrome

The immunologic effects of a year-long therapeutic trial with the synthetic thymic hormone thymopentin were investigated in 29 patients with human immunodeficiency virus--induced lymphadenopathy syndrome. Peripheral T4 and T8 lymphocyte subsets and in vitro immunoglobulin synthesis with pokeweed mitogen (PWM) were monitored before treatment, every 4 months during treatment, and after treatment. Significant increases in circulating T4 cells and a reduction of PWM-induced immunoglobulin suppression were noted in the 21 patients who completed the trial. Furthermore, addition of thymopentin to the in vitro cultures improved the PWM response of T and B cells. After thymopentin treatment, a slight variability of clinical symptoms, including weight loss, diarrhea, night sweats, or a combination of these, was also noted in several subjects.

In vitro inhibition of anti-DNA producing cells from systemic lupus erythematosus patients by autologous anti-F(ab')2 antibodies

We have previously documented an inverse relationship between serum levels of anti-F(ab')2 antibodies and disease activity in systemic lupus erythematosus (SLE). The present study focused on the specific in vitro inhibition of anti-DNA producing cells from SLE patients by autologous anti-F(ab')2 antibodies. Peripheral blood lymphocytes (PBL) from eleven inactive SLE patients with no apparent disease activity were cultured in vitro to evaluate anti-DNA antibody secretion. Low levels of synthesis of anti-DNA antibody were detected in 3 of 11 SLE patients using unstimulated PBL; on the contrary, pokeweed mitogen stimulation of cultured cells increased production of anti-DNA in all SLE subjects. Parallel cultures were also performed in the presence of heterologous and autologous anti-F(ab')2 antibodies and results on production of anti-DNA evaluated. Lymphocytes from SLE patients in remission showed inhibition of synthesis of anti-DNA antibodies when autologous anti-F(ab')2 antibodies were added to the cultures, whereas production of anti-tetanus toxoid IgG by the same cells was not significantly altered under the same conditions. These data suggest that a functional anti-idiotypic role may be assigned to anti-F(ab')2 antibodies during clinical remission of SLE.

Human anti-F(ab')2 antibodies and pepsin agglutinators react with Fv determinants

Affinity-purified human IgG anti-tetanus antibody was subjected to papain and then pepsin digestion, and residual fragments retaining antibody activity were re-isolated by adsorption and elution from Sepharose-tetanus toxoid columns. Both Fab' and Fv fragments isolated by gel filtration showed strong reactivity with anti-F(ab')2 antibodies. Failure of tetanus toxoid to completely block reactivity of anti-F(ab')2 antibody with anti-tetanus Fv fragments indicates that these antibodies react with framework antigens within variable antibody regions.