Certain polyclonal antinuclear antibodies cross-react with the surface membrane of human lymphocytes and granulocytes

Five out of 24 human sera with antinuclear antibody (ANA) titers of 1250 or more contained ANA that bound in vitro to normal viable human mononuclear blood cells and granulocytes, but not to erythrocytes. The antibodies can be eluted off from the cell membranes and shown to possess ANA activity. Antinative DNA antibodies and lupus erythematosus factor were not recovered in eluates, indicating that they did not react with the cells. The cells absorbed 75%-87% of the ANA activity from three sera. ANA reacted with both T-lymphocyte-depleted and -enriched mononuclear cells. No or minimal amounts of ANA bound to mouse spleen cells in suspension; in contrast, the ANA eluted from human cells reacted with nuclei of smeared mouse spleen cells. The cross-reacting antibodies were predominantly IgG that bound well at 37 degrees C, and F(ab')2 fragments carried both activities. The ANA-binding plasma membrane antigen was resistant to trypsin and RNAse but was completely inactivated by glutaraldehyde. The data indicate that human leukocyte plasma membranes and cell nuclei from many species contain a cross-specific antigen. Alternatively, the antigen may be produced in the nucleus and somehow attach to the plasma membrane.

Antinucleosome autoantibodies bind directly to cell lines in vitro and via the FcgammaRIIB receptor to B lymphocytes in vivo: a role for immune complexes in interactions between antinucleosome IgG2a and B cells of BXSB lupus mice

The initial novel observation of this study was that most B cells of male BXSB lupus mice bear surface IgG2a(b) of extrinsic origin. To define the surface antigen, we here examine three (NZBxBXSB)F1-derived IgG2a(b) monoclonal antibodies (mAbs) selected for binding to cell surfaces. Surprisingly, all three mAbs bound the nucleosome (nuc) particle, the fundamental unit of chromatin and an early target of autoimmunity in systemic lupus erythematosus. Their tentative dissociation constant (K(d)) for soluble nuc particles was approximately 7 x 10(-10) m. The mAbs bound more weakly to both H2A-H2B-DNA and H3-H4-DNA complexes, and in immunoblot they stained all four core histones. The mAbs detected a surface antigen on all cell lines examined, present on viable cells. When stripped of nuc, and in the presence of DNase I, their binding to cell lines improved. Heparin displaced the antigen from the cell surface. In vivo, the three mAbs stained B cells of several BALB/c mice clearly stronger than the isotype control; this differential staining was significantly reduced in FcgammaRIIB-deficient mice. The results indicate that the three mAbs recognize (a) planted antigen on viable cultured cells and (b) soluble autoantigen in vivo, leading to immune complexes that bind to FcgammaRIIB. Further experiments demonstrated that antinuc IgG2a could be eluted from splenocytes of a male BXSB lupus mouse. Hence, at least part of the extrinsic IgG2a(b) found on BXSB B cells may represent FcgammaRIIB-bound nuc-IgG2a(b) complexes.

The primary IgM antibody repertoire: a source of potent idiotype immunogens

A widely held view is that, to elicit adaptive immune responses, most protein antigens must be given with adjuvants that activate the innate immune system. It has also been proposed that the immune system is tolerant to idiotypes (Id) of the syngeneic primary antibody (Ab) repertoire. We now show that among 73 purified noncomplexed secretory IgM monoclonal antibodies (mAb), 4 (5.5%) elicited high levels of IgG Ab against the Id even though no adjuvant was added. The responses were controlled by H2-linked immune response genes. IgG1, but no IgG2a or IgG2b, anti-Id Ab were detected, indicating involvement of T helper type 2 (Th2) cells. All 4 IgM mAb are likely germ-line gene-encoded, and 1 was shown to represent a recurrent Id. After endotoxin depletion the most potent immunogen of the 4 still provoked robust humoral anti-Id responses. The results suggest that a natural protein of the primary IgM Ab repertoire can be immunogenic without an adjuvant.

Genes predisposing to autoimmunity augment constitutive major histocompatibility complex class II-associated presentation of the self-antigen IgG2a in vivo

The self-antigen IgG2ab is poorly presented to a gamma2ab 435-451-reactive I-Ad-restricted T-cell hybridoma unless available in high concentrations or targeted to Fcgamma- or complement receptors. Environmental factors, probably the extent of microbial challenge, profoundly influence the constitutive gamma2ab/I-Ad presentation in IgCHb, H-2d mice. Here we report also a strong genetic impact. Constitutive presentation was highly efficient in spleen and thymus of (NZB x BXSB)F1 mice, which inherit a predisposition to develop lupus. Presentation correlated with disease progression and the serum levels of IgG2ab and IgG2ab complement factor 3 complexes. The finding that constitutive presentation was by far most efficient in males indicated that it was augmented by the Y chromosome-linked autoimmune acceleration Yaa gene. In line with previous data for healthy mice, constitutive gamma2ab/I-Ad presentation was most pronounced in the adherent spleen cell fraction and improved by further enrichment for dendritic cells. Notably, however, whereas in normal mice the gamma2ab determinant was undetectable on B cells lacking surface IgG2ab, such B cells contributed considerably to constitutive presentation in (NZB x BXSB)F1 hybrids. Presumably this resulted from complement receptor-mediated internalization of IgG2ab-containing immune complexes formed in lupus. These data add to the evidence that B cells with self-reactive receptors, known to exist in the mature repertoire, may present non-cognate foreign antigen to anti-foreign helper T lymphocytes and thus differentiate into autoantibody-secreting cells, and might likewise account for the polyclonal B-cell activation characteristic of several autoimmune syndromes.

Native IgG2a(b) is barely antigenic to major histocompatibility complex class II-restricted T cells owing to inefficient internalization by professional antigen-presenting cells

Peptide epitopes derived from immunoglobulin variable regions represent tumour-specific antigens on B-cell neoplasms and can be recognized by syngeneic, major histocompatibility complex (MHC) class II-restricted T cells. Immunoglobulin peptide/MHC class II complexes may also be involved in autoimmunity and CD4+ T-cell-mediated B-cell regulation. Thus, the IgG2a(b) H-chain allopeptide gamma2a(b) 435-451 presented on I-Ad mimics the epitope implicated in herpes simplex virus-induced autoimmune stromal keratitis and is the target of T helper 1 (Th1) clones that suppress IgG2a(b) production in vivo. We here report that spleen and thymus cells constitutively present the autologous gamma2a(b) epitope to a gamma2a(b) 435-451/I-A(d) reactive T-cell hybridoma as a function of the animal housing conditions (specific pathogen-free or not) and the serum levels of IgG2a(b). Constitutive presentation in the spleen was predominantly performed by dendritic cells. Whereas spleen cells poorly presented native IgG2a(b) to a gamma2a(b) 435-451/I-A(d) reactive T-cell hybridoma, IgG2a(b) in the form of immune complexes were presented > 200-fold more efficiently owing to internalization via low-affinity FcgammaR on macrophages. The antigenicity could also be improved by homotypic aggregation and by targeting IgG2a(b) to complement receptors on the A20 B-cell lymphoma. Mice without detectable IgG2a(b)-containing immune complexes typically exhibited minimal constitutive presentation. Nevertheless, native IgG2a(b) can sensitize antigen-presenting cells in vivo, as mice that were devoid of immune complexes and carried an IgG2a(b)-producing tumour did present constitutively, even at physiological IgG2a(b) serum levels. Whereas the amounts of IgG released from most B-cell lymphomas may be too low to allow spontaneous priming of tumour-specific MHC class II-restricted T cells, administration of tumour immunoglobulin in aggregated form might improve the efficacy of idiotype vaccination.

The P9 peptide sidechain specificity of I-Ad

The murine MHC class II variant I-Ad confers susceptibility to herpes simplex virus (HSV)-induced keratitis and relative protection against type 1 diabetes mellitus. The association to these autoimmune diseases appears to be largely determined by the peptide sidechain specificity of the P9 pocket, which we therefore have analyzed in detail. Assessment of T-cell responses and I-Ad binding capacity of position 446-substituted analogs of an IgG2a allotype b (IgG2a(b)) heavy chain peptide demonstrates that engagement of the P9 pocket is crucial for effective peptide presentation. Sidechain size rather than charge decides the capacity to engage the P9 pocket. Thus, small, uncharged sidechains are accepted, whereas acidic and aromatic amino acids as well as lysine and arginine are disfavored. The specificity of the P9 pocket of I-Ad (serine beta57) is distinct from that of the diabetes-associated I-Ag7 (aspartic acid beta57), supporting the contention that the polymorphism at residue beta57 influences diabetes susceptibility via P9-specific effects on the repertoires of self peptides presented to T cells. Furthermore, the data rationalize the susceptibility to HSV-induced keratitis conferred by the a and the protection conferred by the b allotypes of the IgG2a heavy chain. Keratitogenic T cells, which cross-react with the viral UL6 protein and a corneal antigen, are silenced in IgG2a(b) mice because of antigenic mimicry with gamma2a(b) 435-451. Our finding that the lysine P9 residue of the corresponding gamma2a(a) allopeptide precludes high-affinity binding to I-Ad indicates that the susceptibility of IgG2a(a) mice reflects inefficient thymic presentation of autologous IgG2a and thus failure to purge the T-cell repertoire of the pathogenic clones.

N-terminal elongation of a peptide determinant beyond the first primary anchor improves binding to H-2 I-Ad and HLA-DR1 by backbone-dependent and aromatic side chain-dependent interactions, respectively

The IgG2a(b) heavy chain allopeptide determinant gamma2a(b) 436-451 (Kabat numbering) presented by the major histocompatibility complex (MHC) class II molecule I-Ad is recognized by T cells which cross-react with a corneal self antigen and with the UL6 protein of the herpes simplex virus which induce autoimmune keratitis, and is the target of Th1 clones that suppress IgG2a(b) production in vivo. In the gamma2a(b) peptide/l-Ad complex, tyrosine438 is the first primary anchor (P1) and residues 440-445 encompass the T cell receptor contact residues. Amino-terminal elongation of gamma2a(b) 437-451 by a single residue (P-2) augmented the I-Ad binding capacity 10-fold and the antigenicity 55-195-fold. This was a function of the peptide main chain, since non-conservative substitutions were accepted. The gamma2a(b) peptide also bound HLA-DR1, and amino-terminal extension by a single aromatic amino acid at P-3 augmented binding 15-fold. The interaction between HLA-DR1 and P-3 specifically required an aromatic peptide side chain, and computer simulations indicated that the aromatic ring at P-3 engaged conserved HLA-DR1 phenylalanine residues at the edge of the peptide binding groove. Thus, these data demonstrate that residues amino terminal to P1 may substantially increase peptide affinity for MHC class II by main chain-dependent as well as side chain-dependent interactions, and imply that the HLA-DR1 motif should be extended to include an aromatic amino acid at P-3.

Immunization with the light chain and the VL domain of the isologous myeloma protein 315 inhibits growth of mouse plasmacytoma MOPC315

Prior immunization of BALB/c mice with free light chains from myeloma protein 315 (L315) and its variable domain (VL315) inhibited the growth of subcutaneously injected MOPC315 tumour cells. The growth suppression observed after immunization with L315 was equivalent to that which resulted from immunization with the complete M315. VL315 and non-polymerized L315 did not elicit specific antibodies. Polymerized L315 induced both suppression of MOPC315 growth and antibodies specific for free L315; however, these antibodies did not react with the complete M315, nor were they absorbed by MOPC315 tumour cells. The data indicate that the suppression of tumour growth was mediated by specifically sensitized cells acting in the absence of antibodies against M315 or L315. Immunization with the variable domain of the heavy chain from M315 (VH315) had no effect on the growth of MOPC315. The M315 fragments and subunits that induced growth suppression were thus identical with those capable of inducing T helper cells in BALB/c mice.

A novel first primary anchor extends the MHC class II I-Ad binding motif to encompass nine amino acids

The MHC class II molecule I-Ad has been reported to bind peptides containing a motif of six consecutive amino acids. We demonstrate that binding of the murine IgG2ab heavy chain allopeptide gamma 2ab 435-451 (Kabat numbering) to I-Ad is strongly enhanced by a novel first primary anchor (P1) three residues N-terminal to this hexamer. This is based on flow cytometric assessment of the I-Ad binding capacity of gamma 2ab peptide analogues, their antigenicity for I-Ad-restricted T cell clones and molecular modelling. The P1 pocket is broadly specific since allphatic, aromatic, acidic, the basic histidine and small polar side chains all allowed good binding. By contrast, asparagine, arginine and glycine reduced the binding capacity 10-, 16- and > 100-fold respectively. Truncation or glycine substitution at P1 decreased antigenicity by a factor > 1000. Nevertheless, I-Ad-restricted T cells are not completely dependent on this anchor since high concentrations of a peptide with glycine-substituted P1 elicited maximal responses. Additional anchoring side chains are found at P4, P6 and P9. The autologous IgG2aa heavy chain shares prominent epitopic residues with gamma 2ab 435-451 at P3, P5 and P8. However, the lysine of gamma 2aa at P9 impairs binding to I-Ad, which may explain why the gamma 2ab allopeptide-reactive T cells escaped negative selection. The data rationalize our observation (Bartnes, K. and Hannestad, K. 1997. Eur. J. Immunol. 27:1124) that these T cells recognize a syngeneic B cell lymphoma, provided its presentation of intrinsic gamma 2aa is enhanced by surface IgG2aa ligation.

A retro-inverso analog mimics the cognate peptide epitope of a CD4+ T cell clone

Synthetic analogs of peptide epitopes may activate specific T helper cells, antagonize their antigen receptors, or block recognition by competing for major histocompatibility complex (MHC) class II binding sites. Rationally designed peptides may therefore prove useful as vaccines and for treatment of autoimmune diseases and allergies mediated by CD4+ T cells. However, their susceptibility to proteolytic degradation limits the applicability of conventional peptides in vivo. By contrast, retro-inverso analogs, in which a native sequence is substituted with D-amino acids linked with a reversed backbone, resist proteolysis and still maintain the side chain topology of the corresponding natural peptide. We report here that an end group-modified retro-inverso analog of the IgG2ab heavy chain allopeptide determinant gamma 2ab 435-447 was recognized by an I-Ad-restricted, gamma 2ab 435-447-reactive T cell clone. The pseudopeptide elicited near-maximal interleukin-2 responses, although 300-fold higher concentrations were needed than the native determinant. The weaker antigenicity of the retro-inverso analog could be fully accounted for by an impaired I-Ad binding capacity, which might reflect reduced ability of the distorted main chain to form hydrogen bonds with I-Ad. Glycine substitution at the residue corresponding to the first primary anchor (P1) of the native peptide abrogated I-Ad binding and antigenicity of the retro-inverso analog. Thus, the pseudopeptide resembled the native determinant with respect to orientation in the class II binding site, configuration of the epitopic side chains, and the constraints that governed the interactions between a major anchoring side chain and I-Ad. In conclusion, proteolytically resistant compounds with predefined capacity to interact with MHC class II allelic products and T cell antigen receptors may be designed by retro-inverso modification of native determinants.

Engagement of the B lymphocyte antigen receptor induces presentation of intrinsic immunoglobulin peptides on major histocompatibility complex class II molecules

By means of the clonotypic variable region, the immunoglobulin (Ig) is a tumor-specific antigen on B cell neoplasms. We report that engagement of the B cell antigen receptor (BcR) promotes presentation of peptides derived from the B cell's intrinsic Ig to major histocompatibility complex (MHC) class II-restricted T cells. Thus, anti-Ig endowed normal, ex vivo B lymphocytes from H-2d, Ig constant heavy chain allotype b (IgCHb) mice with the capacity to stimulate an I-Ad-restricted T cell clone which recognizes the gamma 2ab 435-451 allopeptide. The corresponding self gamma 2aa peptide is cryptic and 6000-fold less antigenic than the gamma 2ab allopeptide. Even so, the syngeneic B cell lymphoma A20 which expresses surface(s) IgG2aa, was also recognized by the T cells after BcR ligation. Thus, anti-Ig triggered the disclosure of a cryptic tumor antigen determinant. We propose that autoantigens, by engaging the BcR of self-reactive B cells, induce presentation of intrinsic Ig peptides to which the T helper cell (Th) repertoire is not tolerant. In this way, B cells with anti-self potential may be activated without Th recognition of nominal autoantigen.

A syngeneic idiotype is immunogenic when borne by IgM but tolerogenic when joined to IgG

Some syngeneic monoclonal antibodies (mAb) elicit immune responses like conventional T-dependent antigens. To find out whether the heavy chain class (isotype) plays a role for the immunogenicity of an idiotype (Id), we isolated rare subclones of an IgM mAb (termed Id3) in which the variable region of the heavy chain (VH) is associated with a new constant region (CH). The VH-Id3 gene is a member of the murine 36-60 family and probably has three replacement mutations. The light chain V gene is germ-line V lambda 2. IgM, IgG1, IgG2a and IgG2b variants of Id3 were purified from protein-free medium and injected without adjuvant into BALB/c mice. The parental 19S IgM mAb given subcutaneously (s.c.) elicited a vigorous humoral response against Id3; in comparison, monomeric 8S IgM was a much weaker immunogen. Unlike IgM, multiple challenges with the IgG switch variants failed to induce anti-Id3 Ab. IgG variants gained immunogenicity if they were purified from medium containing fetal calf serum, mixed with complete Freund's adjuvant or injected into mice primed with IgM-Id3. Pretreatment with 100 micrograms s.c. + 50 micrograms of the IgG2a variant extinguished the Ab response to parental IgM, but the response to adjuvant-free bovine serum albumin was intact. Therefore, the tolerance induced by the IgG2a switch variant is antigen-specific and not due to toxicity. Significant inhibition of the Ab response to parental IgM was observed after treatment with 4 micrograms of the IgG2a switch variant. Administration of the IgG1 and IgG2b switch variants also inhibited this response significantly. Thus, the outcome of an encounter with Id3 is strongly influenced by the CH isotype to which the Id is joined. This suggests novel ways to minimize unwanted Ab responses against Id of human therapeutic mAb. In the context of the theory of Id networks, we suggest that dominant B cell clones can preempt anti-Id Ab responses against themselves by early switching from IgM to IgG secretion, before immunogenic IgM Ab have had time to activate anti-Id B cells.

A human hybridoma monoclonal antibody (TrJ11) recognizing a new HLA-DR epitope shared by DR4, DR8, DR11, and DRB1*1303

The cytotoxic IgM lambda human hybridoma mAb TrJ11 reacts with lymphoblastoid B-cell lines expressing DR4, DR8, DR11, and DRB1*1303. However, TrJ11 was monospecific when normal B cells freshly isolated from blood served as targets in that it only killed HLA-DR4-positive cells. Thus, of 235 HLA-typed persons TrJ11 was strongly cytotoxic for normal B cells of all 90 DR4-positive individuals, but it did not react with B cells from any of the 145 DR4-negative donors. Hence, mAb TrJ11 proved to be suitable for routine DR4 typing. The specific binding of TrJ11 to a DR4-positive cell line was profoundly blocked by the mouse HLA-DR beta chain-specific monomorphic mAb TAL 14.1, indicating that the epitope recognized by TrJ11 is located in the DR beta chain. The possibility that amino acids located in the floor of the peptide-binding site are critical for the TrJ11 epitope is discussed.

Identification of the gene encoding a novel HLA-B39 subtype. Two amino acid substitutions on the beta-sheet out of the peptide-binding floor form a novel serological epitope

Serological analysis suggests the existence of a novel HLA-B39 subtype (HLA-B39N) in the Japanese population. To identify this novel allele, a gene encoding HLA-B39N was cloned and the exons were sequenced. A gene encoding HLA-B39N (B*3904) and B*39011 differs by two nucleotide substitutions at codons 11 and 12 whereas B*3904 and B*39013 differ by three nucleotide substitutions at codons 11, 12, and 312. One nucleotide difference at codon 11 produces a change from serine in B*3901 to alanine in B*3904 whereas another difference at codon 12 changes valine in B*3901 to methionine in B*3904. The residues 11 and 12 are located on the beta-sheet out of the peptide-binding floor and are completely buried in the molecule. These results suggest that the substitutions at these residues alter the conformation of other residues forming epitopes of alloantibodies. Analysis of HLA-B*3901 genes in the Japanese population showed that both B*39011 and B*39013 were observed in the Japanese population. The present study suggests that B*3904 may have evolved from B*39011 rather than B*39013.

A novel HLA-A determinant recognized by a cytotoxic human hybridoma IgG1 monoclonal antibody (TrJ14)

TrJ14 is a cytotoxic human IgG1 lambda hybridoma mAb that recognized a novel HLA-A epitope expressed by lymphoblastoid B cells that are homo- or heterozygous for A2, A3, A11, A30, A31, A33, A68 and A69. Based on these results, the HLA type of cell line TEM (10w9057) was retyped as A66. When peripheral blood T cells isolated freshly from 265 HLA-typed normal individuals served as targets, TrJ14 killed cells expressing two TrJ14-positive HLA-A alleles, as well as the majority of cells having one TrJ14-positive and one TrJ14-negative HLA-A antigen. However, TrJ14 failed to recognize or reacted weakly with most HLA-A2 and -A3 heterozygous normal T cells when A2 or A3 was coexpressed together with a TrJ14-negative antigen. The serological reactivity of TrJ14 correlated with the amino acid valine and aspartic acid at positions 76 and 77 of the alpha 1-domain helix. These amino acids were shared exclusively by all the identified TrJ14+ alleles.

A cytotoxic human hybridoma monoclonal antibody (TrJ6) defining an epitope expressed by HLA-DQ4 and -DQ5

We have generated a cytotoxic human hybridoma monoclonal IgM lambda antibody, designated TrJ6, that is specific for a new epitope shared by HLA-DQ4 and -DQ5. TrJ6 strongly killed all ten DQ4-bearing cells and weakly killed all four DQ5-bearing cell lines. In contrast, none of the 36 cell lines lacking DQ4 and DQ5 antigens was recognized by TrJ6. This was confirmed by fluorescence cytometry. The specific binding of TrJ6 to a DQ4-bearing line was efficiently blocked by IIB3 (murine anti-DQ8+9+4+5+6 mAb) and TrG6 (human IgG mAb against DQ4+5+6), confirming that TrJ6 is specific for a polymorphic DQ epitope. TrJ6 can be used to distinguish DQ5+ from DQ6+ B-lymphoblastoid cells. DQ4 beta and DQ5 beta chains share one unique residue (Ser-74) and one relatively unique residue (Val-75), which may therefore need to be coexpressed in order for the TrJ6 epitope to be formed. Alternatively, Ser-74 alone contributes critically to the allospecificity of this epitope. In addition, one or more of three residues unique for DQ4 (Leu-56, Glu-70, and Asp-71 on the DQ4 beta chain) could also contribute to the TrJ6 epitope because TrJ6 reacted stronger with DQ4- than with DQ5-bearing cell lines.

Th1 clones that suppress IgG2ab specifically recognize an allopeptide determinant comprising residues 435-451 of gamma 2ab

We have previously reported that gamma 2ab/I-A(d)-specific Th1 clones from BALB/c mice (gamma 2aa, H-2d) mediated a long-lasting, selective suppression of serum IgG2ab levels when transferred to newborn (BALB/c x B10.D2)F1 (gamma 2a/b, H-2d) mice (Bartnes, K. and Hannestad, K. Eur. J. Immunol. 1991. 21: 2365). We here analyze the peptide specificity of hybridomas derived from two suppressive T cell clones. The shortest synthetic peptide with optimal antigenicity comprises gamma 2ab residues 435-451 (Kabat numbering). The determinant core encompasses the gamma 2ab 440-446 (KLRVQKS) sequence which contains an I-A(d) allele-specific motif. Challenge with single amino acid-substituted gamma 2ab 435-447 analogs revealed that residues K440, R442 and K445 which are shared by the autologous and allogeneic gamma 2a, as well as residues Q444 and S446 which represent allogeneic differences, are critical for recognition. We obtained evidence that K440, R442 and Q444 are epitope residues, while K445 and S446 contribute to anchoring of the peptide to I-A(d). Amino acids located outside of the core also influence antigenicity, the most striking effect being a 340-870-fold augmentation of potency when gamma 2ab 437-451 is extended by F436. IgG2ab required processing in order to stimulate the hybridomas. The data support the contention that the Th1 clones specific for Fc of gamma 2ab mediated IgG2ab suppression by cognate interaction with sIgG2ab+ B cells that presented a C gamma 2ab peptide(s) derived from their endogenous Ig on major histocompatibility complex class II. The T cells cross-reacted weakly with peptide 435-451 of the autologous gamma 2aa allotype. This opens the possibility that self-peptides from Ig C regions can target B cells for regulatory interactions with autologous Th cells.

A cytotoxic human hybridoma monoclonal antibody (TrJ5) specific for HLA-B38(16) and -B39(16)

We have generated a cytotoxic IgM lambda human hybridoma mAb (TrJ5), that is specific for HLA-B38(16) and -B39(16). Among a panel of 42 HLA-defined cell lines, TrJ5 killed all five B38-positive and both B16-positive cell lines, as well as the single B39-positive cell line, but not any cell lines lacking these antigens. It could be ruled out that the TrJ5 epitope is located on the alpha 1 domain because TrJ5 did not react with cells bearing HLA-B14, the alpha 1 domain of which is identical to alpha 1 of B39. In the alpha 2 domain of B38 and B39, a unique threonine residue at position 158 (Thr-158) is not shared by any of 29 other HLA-B alleles. This suggests that Thr-158 of the alpha 2-domain helix is critical for the TrJ5 epitope.

A human monoclonal hybridoma antibody (TrJ1) specific for HLA-DQ2

TrJ1 is a cytotoxic human hybridoma mAb (IgM lambda). Its reaction pattern with a panel of 42 HLA-defined lymphoblastoid B-cell lines correlated precisely with expression of DQ2. By flow cytometry it was shown that the binding of TrJ1 to DQ2 was efficiently blocked by the murine anti-DQ2 mAb 358.4, indicating that the TrJ1 and 358.4 epitopes overlap. TrJ1 reacted much better with EBV-transformed B cells than with B cells freshly isolated from blood. TrJ1 seemed suitable for typing freshly isolated B cells provided the incubation with complement lasted for 115 min in Terasaki plates. One or more of the DQ2-specific polymorphic amino acids E46, F47, L52, L55, K71 or A74, situated on the alpha-helix of the DQ2 beta chain, are probably critical for the TrJ1 epitope.

Mapping of an epitope defined by a human hybridoma antibody (TrD3): a new HLA-B supertype associated with a subset of HLA-Bw6

The new human-human hybridoma TrD3 secretes a cytotoxic IgM mAb, which reacted with 28 of a panel of 56 HLA-typed lymphoblastoid cells. All 28 TrD3+ cells expressed the HLA-B supertype Bw6, whereas 10 Bw6+ cells were not recognized by the mAb. None of the 17 Bw4 homozygous cells were positive with TrD3. Thus, TrD3 divided the Bw6+ HLA-B specificities of the cell lines into two subgroups, namely, Bw6+TrD3+ and Bw6+TrD3-, and therefore defines a new HLA-B supertype. TrD3 reacted strongly with some B8+ cell lines and weakly or not at all with others, suggesting a new split of HLA-B8. Compared with cell lines, TrD3 reacted more weakly with freshly isolated T cells from blood. The Bw6-specific rat mAb SFR8-B6 partially blocked the binding of 125I-labeled TrD3 to a Bw6+ cell line. By using cell lines transfected with hybrid genes between HLA-B7 (Bw6+) and HLA-B27 (Bw6-) as targets in flow cytometry, critical residues for the TrD3 epitope could be mapped to the amino acid region 24-62 of the HLA class-I alpha 1 domain. Comparison of deduced amino acid sequences of TrD3-positive and -negative cells indicated that a tryptophane residue at position 95 destroyed the TrD3 epitope, and that one or more of the residues in positions 24, 45, and 46 may be critical, suggesting that it is a discontinuous epitope. It is notable that none of these residues are located on alpha-helixes.(ABSTRACT TRUNCATED AT 250 WORDS)

A cytotoxic monoclonal human hybridoma antibody (TrJ3) against HLA-B44(12) and -B45(12)

We have generated a human monoclonal cytotoxic IgM lambda antibody (TrJ3) that reacted specifically with all lymphoblastoid B-cell lines expressing HLA-B44(12) and B45(12). TrJ3 hybridoma supernatant was suitable for HLA-B12 typing of freshly isolated blood mononuclear cells. Analysis of available amino acid sequences of HLA-B molecules indicated that the alpha 1 domain does not contain the TrJ3 serological epitope. Since HLA-B44 is associated with a unique serine residue at position 167 that points towards the peptide binding groove, we propose that S167 of the alpha 2 domain helix is a critical part of the TrJ3 epitope.

Anti-idiotypic immune responses against adjuvant-free isologous IgM monoclonal antibodies and their augmentation by complex formation between IgM and albumin in bovine serum

In previous studies we demonstrated that the hypermutated isologous myeloma protein MOPC 315 (isotype IgA; lambda 2) is recognized by T helper cells like an ordinary foreign protein antigen. To what extent can an immune system recognize and respond to V domains from the primary (pre-immune) repertoire? To study this question we made 21 BALB/c hybridoma anti-2,4,6 trinitrophenyl monoclonal antibodies (mAb) of IgM; lambda isotype. All mAb purified from supernatants containing fetal bovine serum had formed spontaneous complexes with bovine serum albumin possibly by way of disulfide interchange. Twenty of twenty-one mAb from this source elicited IgG1 anti-idiotypic (Id) Ab when given as a single adjuvant-free dose of 200 micrograms. For 12 of them even 10 micrograms was sufficient. This indicated that BSA augmented the anti-Id responses by a carrier effect. Three of the mAb were therefore purified from ascites fluid and from serum-free medium. Only one of them then induced humoral anti-Id responses in BALB/c mice when given as a single adjuvant-free dose of 100 micrograms. The other two became immunogenic when emulsified in Freund's complete adjuvant. The results indicate that some IgM mAb exist whose Id determinants alone can elicit substantial anti-Id responses because they are recognized like ordinary foreign protein antigens. Since albumin in fetal bovine serum forms complexes with IgM and greatly augments its immunogenicity, serum-free medium should be used for production of human or humanized therapeutic IgM mAb. A possible role for Id for IgM Ab as cardinal autoantigens is discussed.

Igh-1b-specific CD4+CD8- T cell clones of the Th1 subset selectively suppress the Igh-1b allotype in vivo

The demonstration of major histocompatibility complex (MHC)-restricted T helper (Th) cells specific for peptides from the variable (V) regions of syngeneic immunoglobulin (Ig) (idiopeptides) opens the possibility that Th cells regulate B cell functions via idiopeptide-based cognate T-B interactions. As a model for such interactions we investigated the influence of Ig allotype-specific T cells on the differentiation of H-2-syngeneic B cells expressing that particular Ig allotype. We established a BALB/c (H-2d, Iga) CD4+CD8- T cell line and clones of the Th1 subset (interleukin 2+, interleukin 4-, interferon-gamma+, tumor necrosis factor-alpha+) that recognized Igh-1 (IgG2a) of the b allotype (Igh-1b) together with I-Ad. These T cells specifically suppressed surface Igh-1b+ B cells in vitro and in vivo. In 12 out of 15 6-week-old (BALB/c X B10.D2)F1 mice neonatally injected with Igh-1b-specific T cells, the serum Igh-1b concentrations were less than 5% of the levels in the controls. Thus, allotype suppression can be accomplished solely by adoptive transfer of Igh-1b-specific CD4+ T cells. The in vivo suppression was specific for Igh-1b+ B cells as the recipients' levels of Igh-1a and Igh-4b (IgG1b) were unaffected. The V beta 14-specific anti-T cell receptor (TcR) monoclonal antibody 14-2 inhibited activation of hybridomas derived from two of the clones. Collectively the data indicate that suppression resulted from cognate interactions between allopeptide-specific TcR alpha/beta+ T cells and normal unmanipulated B lymphocytes presenting their endogenous Igh-1b in association with MHC class II molecules. The data support the possibility that normal B cells can be suppressed by idiopeptide-specific T cells in vivo.

Epitope mapping of human monoclonal antibodies to HLA-B27 by using natural and mutated antigenic variants

The epitopes defined by three human monoclonal antibodies (mAbs) (Tr3B6, TrCG10, TrBH12) against HLA-B27 have been mapped by flow cytometry. For this purpose we used murine transfected cells expressing at their surface hybrid antigens between HLA-B7 and -B27 and, in addition, Epstein-Barr virus cell lines expressing the six HLA-B27 alleles B*2701 to B*2706. The results indicated that the mAbs are domain specific. TrBH12 recognizes the first external (alpha-1) domain. Residues critical for the TrBH12 epitope are located in the alpha-1 helix and include the polypeptide stretch 63-76 plus a critical amino acid at position 77. Tr3B6 binds the second external (alpha-2) domain, and one mutation (VAL152----GLU152) destroyed its epitope. TrCG10 also binds the alpha-2 domain.

A supertypic HLA-DP specificity defined by two human-human hybridoma antibodies (TrB50; TrE11)

We here report two human-human hybridoma antibodies: TrB50 (IgG) and TrE11 (IgM), derived from the same donor. They displayed an identical reaction pattern with 76 Epstein-Barr virus-transformed cell lines. Of these, 29 lines were completely HLA-typed and both antibodies recognized all cells expressing DPwl (six lines), DPw3 (five lines), or DPw5 (three lines). In addition, they bound to one out of four DPw2+ cells and three out of four DPblank+ cells. This specificity correlated strikingly with a characteristic DP beta amino acid sequence (DEAV) at positions 84-87 that had been determined by others. Binding of 125I-labeled TrB50 to lymphoblastoid cells was inhibited by unlabeled IVA-12 (anti-DR + DP monomorphic) and by TrE11. Furthermore, antigens in lysates from TrB50+TrE11+ cells cross-linked TrB50 and TrE11 to the monomorphic anti-DP monoclonal antibody B7/21. Collectively the data provide strong evidence that the epitopes reside on DP molecules. TrE11 can be used to type for this DP beta supertypic specificity by microcytotoxicity using isolated blood B lymphocytes as targets or by a rosette assay directly on whole blood.

A cytotoxic human-human hybridoma antibody (TrC7) specific for HLA-A29

TrC7 is a cytotoxic IgM human-human hybridoma anti-HLA Ab. Its reaction pattern with a panel of 48 HLA-typed EBV-transformed cell lines and PBMC from 348 HLA-typed individuals correlated precisely with expression of HLA-A29. TrC7 did not react with HLA-A30, -31, -32 or -w33, which, like A29, are splits of Aw19.

Two cytotoxic human-human hybridoma antibodies to HLA: TrAH10 (anti A3.1) and TrAG2 (anti B7, Bw42)

Two cytotoxic human-human hybridoma IgM antibodies to HLA were generated by EBV transformation of PBMC from multiparous women and fusion of EBV transformed cells with the human fusion partners KR4 or KR12. Both mAbs required the sensitive immunomagnetic cytotoxicity method to display killing of freshly prepared PBMC. One mAb (TrAH10) was specific for HLA-A3. Strikingly, TrAH10 reacted much more strongly with lymphoblastoid cell lines of HLA-A3.1 than of the rare variant HLA-A3.2, previously detected by cytotoxic T cells. Thus, in the microcytotoxicity test, the titer of concentrated TrAH10 was approximately 2000 times higher for A3.1 as compared to A3.2, and a clear difference was also observed in radioimmunoassay. Since the two HLA-A3 variants differ by only two amino acids at positions 152 and 156 of the alpha 2-domain's alpha-helix, the epitopes defined by the mAb TrAH10 and HLA-A3.1 specific cytotoxic T cells must be closely related. The observations with TrAH10 suggest that the HLA polymorphism detected by human mAbs may turn out to be as extensive as the T-cell defined HLA polymorphism. The other mAb (TrAG2) bound B7 and Bw42 with equal strength, and in addition bound weakly to some cells that were Bw22 or B39. Magnetic polymerbeads coated with affinity purified human mAbs TrAH10 or TrAG2 formed rosettes with EBV transformed cells carrying relevant HLA antigens; however, rosette formation with freshly isolated PBMC was very weak and unsuitable as a typing assay.

Multiple sclerosis patients have a high frequency of an HLA-DQ beta epitope defined by a human-human hybridoma antibody

Epstein-Barr virus (EBV) transformed B-cells from patients with multiple sclerosis (MS) and healthy controls were analysed for reactivity with the HLA-DQ-specific human-human hybridoma Ab TrB12 (anti-DQw6 + DQw8 + DQw9) by indirect immunofluorescence (IIF). Positive results were obtained with 34 out of 35 MS patients (97.1%) and 79 out of 106 controls (74.5%) (p less than 0.005, RR = 11.6). Thus, DQ molecules that express the TrB12 epitope may contribute to the susceptibility to develop MS.

Direct HLA typing by rosetting with immunomagnetic beads coated with specific antibodies

Paramagnetic monodisperse polymer beads were coated with purified human hybridoma antibodies specific for polymorphic HLA determinants. The mAb-coated beads bound specifically to cells from individuals with the relevant HLA type. The rosettes formed by beads and cells were isolated with a magnet. Rosette formation was evaluated microscopically and used as criterion for positive typing. By this rosette assay, fast and reliable HLA typing of whole blood was possible.

Two HLA-DQ-specific human-human hybridoma antibodies (TrG6;TrC5) define epitopes also expressed by a transcomplementing hybrid DQ molecule (DQw7 alpha/DQw4 beta)

We have generated two IgG human-human hybridoma Abs, TrG6 and TrC5, that define subsets of HLA-DQ. TrG6 combined selectively with lymphoblastoid cell lines that expressed DQw1 or DQw4. By sequential immunoprecipitation, competition with other mAbs of defined specificity for binding to antigen, and experiments where HLA antigens from cell lysates crosslinked pairs of mAbs, it was established that TrG6 bound a DQ-molecule. mAb TrC5 specifically recognized DQw2+DR3+ and DQw7+DR5+ cells. The reaction pattern of TrC5 with HLA-loss mutants indicated that TrC5 bound to DQw2 of the DQw2+DR3+ haplotype. Antigens in lysate from DQw7+DR5+ cells crosslinked TrC5 to the murine mAbs Tü22 (anti-DQ monomorphic) and IVD-12 (anti-DQw7 + DQw8 + DQw9), demonstrating that on these cells the TrC5 epitope is located on DQw7 molecules. Lysates from DQw7+DR5+/DQw4+DRw8+ heterozygous cells crosslinked TrG6 and TrC5, and available evidence indicated that the epitopes defined by these two mAbs were expressed by the transcomplementing DQ-molecule DQw7 alpha/DQw4 beta, where the DQw7 alpha chain specifies epitope TrC5 and the DQw4 beta chain specifies epitope TrG6. Taken together with published nucleotide sequences of DQ alpha and beta genes, our data are consistent with the conclusion that the amino acids at positions 69 and/or 75 of the DQ alpha chain of DQw2+DR3+ and DQw7+DR5+ haplotypes are critical for epitope TrC5. The previously reported human-human hybridoma Ab TrB12 reacts with DQw6, DQw8, and DQw9. The specificity of the murine mAb IIB3 is similar to that of TrB12, but, unlike TrB12, IIB3 also binds DQw4+ cells.

Four cytotoxic human-human hybridoma antibodies that react with HLA-B27

PBMC were isolated from a multiparous woman with HLA-B27 specific Abs in her serum. The HLA type of the donor was A2,9:B7. The PBMC were EBV transformed, and four cell lines making cytotoxic Abs to HLA-B27+ cells prepared. Hybridomas were constructed by fusing the EBV lines with the human fusion partner KR4. All four mAbs were of IgM isotype. One mAb (TrBH12) reacted specifically with B27+, B37+ and Bw47+ lymphoblastoid cell lines and with all B27+ PBMC except for a rare variant so far found only in one Norwegian family. Another mAb (Tr3B6) was cytotoxic for all B27+ cells tested, including the TrBH12- variant; in addition, it showed weaker cross-reactions to Bw42, B49 and a cell line with the probable phenotype B7,38. Supernatant from the Tr3B6 hybridoma was tested in lymphocytotoxicity against a panel of 658 individuals, 141 of whom were B27+. With this panel, Tr3B6 showed perfect correlation with HLA-B27. The two last mAbs (TrCG10 and TrBF1) reacted with all B27+ cells tested, but in addition showed quite extensive cross-reactions.

Immune responses to an adjuvant-free native syngeneic myeloma protein (M315)

Myeloma protein 315 (M315; isotype IgA, lambda 2) is used in this report as a model to explore the immunogenicity of a syngeneic Ig under nearly physiological conditions. We have previously shown that a synthetic peptide spanning the mutated HV3 loop of the L-315 chain, when emulsified in complete Freund's adjuvant, elicits T helper cells (Th) that respond to a boost with L-315 or M315, indicating that M315 is recognized as a processed protein antigen. We now show that the adjuvant-free 7S monomer of native or of mildly reduced and alkylated M315, given in divided doses totalling 300 or 800 micrograms to BALB/c mice, induced persistent anti-M315 antibodies (Ab), a large part of which was IgG1 directed mainly to idiotypes (Id) associated with M315's hapten-binding site. Polymers of M315 IgA (800 micrograms) failed to induce Ab, due probably to their rapid clearance into bile. Short-term treatment with anti-CD4 monoclonal Ab GK1.5 at the time of priming with 7S M315 inhibited the responses almost completely. The spleens of M315-immune mice contained Th that recognized the L-chain subunit of M315 as a carrier indicating that these Th did not require an assembled (VH-VL) pair of 315 V regions to be activated. We also observed low amounts of Ab specific for epitopes of the C alpha region. This evidence opens the possibility that a distinct autoimmune pathway exists for elicitation of rheumatoid factor (RF; autoAb to Fc gamma) that involves help to RF-producing B cells by Id-specific Th. We suggest that these Th recognize V-region peptides from IgG that have been captured, processed and presented by these B cells.

Minimal expression of blood group A antigen on thrombocytes from A2 individuals

Two multiply transfused group O patients developed refractoriness to random-donor platelet transfusions. Both had high-titer IgG antibodies to group A and B antigens. Subsequent transfusions with ABO-compatible platelets were successful, suggesting that the ABO blood group system is significant in the development of refractoriness to platelet transfusions. By indirect immunofluorescence, the patients' IgG anti-A reacted with platelets from group A1 donors but not with those from group A2 donors. A2 platelets were at least 38 times less efficient at adsorbing a mouse monoclonal anti-A; the difference between the adsorbence capacities of A2 and O platelets was minimal. Transfusion of A2 platelets, unlike that of A1 platelets, effected a good increment in the platelet counts of these two patients. The results indicate that the expression of A2 antigen on platelets from A2 subjects is minimal.

A cytotoxic human-human hybridoma antibody (TrH6) specific for HLA-DRw52

TrH6 is a new human-human hybridoma antibody (Ab) of IgM, lambda isotype. At concentrations of 17-5000 ng IgM/ml, TrH6 killed twelve out of fourteen lymphoblastoid cell lines that expressed DRw52, but none of the nine DRw53 homozygous lines. Both DRw52+ cells (LUY, TAB) not killed by TrH6 were DR8+, suggesting that these lines express a structural variant of DRw52 linked to DR8. The murine cytotoxic DRw52-specific mAb 7.3.19.1 (Koning et al. 1984) exhibited the same pattern of reactivity with DRw52+ cells as TrH6. However, unlike TrH6, 7.3.19.1 cross-reacted weakly with two DR7+DRw53+ homozygous cell lines, suggesting that the TrH6 epitope has a more limited distribution. The reactions with a panel of cells with known deletions in the HLA-region supported the conclusion that TrH6 is specific for DRw52. Further evidence was obtained in a competition RIA, where the murine mAbs L243 (anti-DR monomorphic) and 7.3.19.1 (anti-DRw52) inhibited binding of radiolabeled TrH6 to DRw52 homozygous cells. TrH6-coated magnetic beads provided a simple rosette-assay for typing of "buffy-coat" leukocytes for the TrH6 epitope.

Are idiotypic peptides from variable domains critical for T-dependent production of rheumatoid factors?

Studies from this laboratory have indicated that isologous myeloma protein 315 (M315, isotype IgA, lambda 2) elicits T helper cells which recognize processed forms (peptides) of its V-domains and that recognition is controlled by H-2 linked immune-response (Ir) genes (J Exp Med 1982; 155:1587-96; Eur J Immunol 1986; 16:889-93). We now report that adjuvant-free soluble M315, particularly the mildly reduced and alkylated form, stimulates a T-dependent antibody response mainly specific for M315's paired V-domains. A small subset of the antibodies appeared to recognize the C-region of IgA, thus being analogous to rheumatoid factors (RF). On the basis of these observations, we propose that one pathway to RF production depends on T helper cells that interact directly with RF-producing B cells across peptide-MHC bridges. These peptides are envisaged to be derived from hypervariable regions of IgG V-domains, and they are therefore called "idiotypic peptides". This hypothesis assumes that the number of different idiotypic peptides is so large that the immune system has not developed tolerance to all of them.

A human-human hybridoma (Tr7E2) producing cytotoxic antibody to HLA-DQw1

A human-human IgM (lambda) hybridoma antibody (called Tr7E2) was constructed by fusing Epstein-Barr virus-transformed cells from a multiparous woman with the human fusion partner KR12. By eosin exclusion microcytotoxicity the monoclonal antibody killed 12 of 13 human leukocyte antigen DQw1-bearing lymphoblastoid cells. No reaction was seen with any of 19 DQw1-negative cells. The single DQw1+ cell line that was not killed by Tr7E2 was the homozygous cell called 9WS 806 TAB (DR8,8; DQw1,1) of Japanese origin. The radioimmunoassay indicated that this result was probably not because of a decreased expression by this cell of DQ antigens, and these cells were killed by the mouse monoclonal antibody Genox3.53G2a5, reported to be specific for DQw1. Thus, the Tr7E2- cell line TAB probably expresses a novel structural DQw1 variant. Of 213 Norwegians, 107 were Tr7E2+ Genox+; none expressed only one of these epitopes. The putative split is, therefore, probably very rare in this population. Monodisperse magnetic polymer beads coated with Tr7E2 formed rosettes selectively with peripheral blood mononuclear cells from DQw1-positive individuals, suggesting a new approach to typing for class II antigens.

A human-human hybridoma antibody (TrB12) defining subgroups of HLA-DQw1 and -DQw3

We have constructed an IgG, kappa human--human hybridoma Ab(TrB12), which precipitates a molecule consisting of two polypeptides of about 33 and 27 kD in size. TrB12 reacted with; (1) 7 out of 10 DQw1-positive cell lines in IIF, and all 10 in a rosette-assay; (2) 5 out of 12 DQw3-positive cells, both in IIF and the rosette-assay; (3) none of 4 DQw2 homozygous cells. Detergent cell lysate of DQw1 homozygous cell lines contained antigens that cross-linked the mouse monoclonal antibody Genox 353 G2a-5 (anti-DQw1) and TrB12. TrB12 competed with the mouse DQw3-specific monoclonal antibody IVD-12 for binding to DQw3 homozygous cells. The data imply that the TrB12 epitope is associated with molecules that carry DQw1 and DQw3 serological specificities. By radioimmunoassay, TrB12 and the mouse monoclonal antibody IIB3 divided both DQw1- and DQw3- bearing cell lines into three phenotypic groups: (1) TrB12+IIB3hi, (2) TrB12-IIB3lo, and (3) TrB12-IIB3-. For DQw1 the results suggest that the first two groups represent structural variants but the third group may reflect low expression of DQw1. For DQw3 the evidence suggests that all three phenotypes represent structural variants. DQw3 has previously been divided into two serologically defined alleles, TA10+IIB3- and TA10-IIB3+. The TrB12+IIB3hi and TrB12-IIB3lo variants of DQw3 described in this study probably represent novel subgroups of the TA10-IIB3+ allele.

Simple rosette assay for HLA-B27 typing of whole blood samples

Two human IgM monoclonal antibodies (TrBH12 and Tr3B6) specific for HLA-B27 were coupled to magnetic monodisperse polymer beads by spontaneous adsorption. A few minutes after mixing the beads with 50 microliter of whole blood, rosettes had formed specifically with leucocytes from HLA-B27 positive individuals. In this simple way, reliable typing for HLA-B27 could be conducted rapidly (in about 20 min) by evaluation of rosettes with an inverted microscope and ordinary light. The method requires purified monoclonal antibodies.

Two M315 idiotopes defined by isologous monoclonal antibodies: one depends on germline and the other on mutated murine lambda 2 light chain sequences

We have previously reported that T helper cells of BALB/c mice recognize the unique mutated sequence Phe94, Arg95, Asn96 of the lambda 2 L chain of isologous (BALB/c) myeloma protein 315. Here we study two Id (Id-315.1.4 and Id-315.TH) of the DNP-Lys binding M315 defined by two monoclonal isologous anti-Id Ab (Ab 2-1.4 and Ab 2-TH). Both Id were (1) totally expressed by Fv-315, but not by free unpaired V domains, (2) specifically dependent on VH-315, since lambda 2-315 recombined with four other H chains did not express the Id, (3) related to the hapten-binding site because their expression was blocked by the haptens DNP-Lys and DNP-Gly, and (4) topographically related because Ab 2-1.4 and Ab 2-TH competed with each other for binding to M315. The contribution of lambda chain V regions was studied with the aid of reconstituted Ig molecules of H-315 paired with lambda 1, lambda 2, and lambda 3 L chains. Id-315.TH was expressed equally well by reconstituted Ig containing three different lambda 2 chains (lambda 2-5-7, lambda 2-T952, and lambda 2-315), but its expression was profoundly reduced when H-315 was associated with lambda 3-SAPC15 or lambda 1-J558 L chains; it therefore depended upon amino acids encoded by germline lambda 2 genes. By contrast, Id-315.1.4 was only restored by the lambda 2-315 chain paired with H-315. Since lambda 2-5-7 and lambda 2-T952 differ from lambda 2-315 at positions 38, 94, 95, 96, and 98 or 99, respectively, Id-315.1.4 probably requires the unique mutated amino acids Phe94, Arg95, Asn96 of lambda 2-315. This resembles the effects on Id expression of previously reported unique amino acids of the D region. We failed to confirm that hyperimmunization of BALB/c mice with Ab 2-1.4 cross-linked to KLH induced M315-like Ab. The results are discussed in terms of the contribution of the third hypervariable loop of lambda chains to Id and the immunogenicity of isologous Ig.

A human-human hybridoma producing cytotoxic antibody to HLA-B15, cross-reacting with B17, B5, B35 and B18

Mononuclear blood cells from a multiparous woman were transformed with Epstein Barr virus, and a cell line (Tr2D8) producing anti-HLA antibody was obtained. This cell line was immortalized by hybridization to the human fusion partners KR4 and KR12. While the EBV line died after 7 months, the hybridomas have remained stable for 13 months. The EBV line supernatant (40 micrograms IgM/ml) lysed peripheral blood mononuclear cells (PBMC) bearing B15, B17, B5 and B35. Consistent lysis of B18 bearing cells was only observed with lymphoblastoid cell lines. The supernatant from the Tr2D8 (EBV line X KR4) hybridoma (2.7 micrograms IgM/ml) only lysed B15 bearing PBMC. At a concentration of 13.5 micrograms IgM/ml, the hybridoma antibody lysed lymphoblastoid cell lines bearing B15, B17, B5, B35 and B18.

Synthetic peptides and beta-chain gene rearrangements reveal a diversified T cell repertoire for a lambda light chain third hypervariable region

Twelve L3T4+ Ly-2.2- subclones, derived from 4 independent BALB/c T cell lines, responded to a combination of the I-Ed molecule and a synthetic peptide corresponding to residues 91-108 of the lambda light chain from BALB/c myeloma protein M315 (alpha, lambda 2). Peptide analogues in which the mutated residues Arg95 or Asn96 were exchanged with the corresponding germ-line-encoded Ser95 or Thr96 had an abolished or greatly reduced capacity to stimulate T cell clones. However, responses of subclones to an analogue where the mutated Phe94 was substituted with the germ-line-encoded Tyr94 revealed three specificity patterns: 5 clones reacted only with the lambda 2(315) peptide, 6 clones responded equally well to both peptides and a single clone reacted better with the Tyr94 analogue. Analysis of the T cell receptor beta-chain gene rearrangements disclosed 7 distinct rearrangements, identical rearrangements only being found for subclones originating from the same line. At least 3 different V beta genes were used. Subclones with identical or nearly identical peptide specificity, major histocompatibility complex-restriction and alloreactivity could differ in their V beta or J beta gene segment utilization.

The T lymphocyte response to syngeneic lambda 2 light chain idiotopes. Significance of individual amino acids revealed by variant lambda 2 chains and idiotope-mimicking chemically synthesized peptides

In the present study we have investigated the structure of the helper T cell (Th)-defined idiotope (Id) of myeloma protein 315 lambda 2 light chain (lambda 2(315] in BALB/c (H-2d) mice which carry a high-responder immune response gene for this Id. Three peptides were synthesized which spanned the third hypervariable region (HV3) of lambda 2(315): peptides 88-99, 94-108 and 91-108. Only peptide 91-108 was capable of eliciting carrier-specific Th that recognized M315 or free lambda 2(315). These Th did not recognize lambda 2(5-7) chain which differs from lambda 2(315) at 4 positions in this region; these are Tyr94, Ser95, Thr96, Tyr98 for lambda 2(5-7) and Phe94, Arg95, Asn96, Phe98 for lambda 2(315). Immunization with peptide analogues revealed that substitution of Tyr for Phe94 was compatible with Id-lambda 2(315) mimicry, but substitution of Ser for Arg95 or Thr for Asn96 destroyed the Th-recognized Id. Furthermore, Th primed with lambda 2(5-7) chain did not cross-react with lambda 2T952; these lambda 2 chains only differ from each other at positions 98 and 99 at the V lambda 2-J lambda 2 junction. The data indicate that individual amino acids of short peptide segments are critical for Th-recognized Id of the lambda 2 HV3 loop and V lambda 2-J lambda 2 junction. Furthermore, the immunogenicity of a small peptide suggests that the carrier (lambda 2)-specific Th recognize Id that have been processed by antigen-presenting cells (APC). This implies the existence of two categories of "internal images" of foreign or of self antigens: (a) serologically defined and (b) T lymphocyte defined. We propose that as a rule, Id processing by APC, including B cells, destroys the first and reveals the second category. The possible physiological function of these Id-specific T cells in network interactions with B cells is discussed.

T helper cell recognition of idiotopes on lambda 2 light chains of M315 and T952: evidence for dependence on somatic mutations in the third hypervariable region

Previous work has indicated that BALB/c T helper cells (Th) recognize an idiotope expressed on a 88-114/117 fragment of V lambda 2 of BALB/c myeloma protein 315. In the present study the antigenic structure of this idiotope was further analyzed. Conventional carrier-specific Th elicited by immunization of BALB/c mice with free lambda 2(315) did not cross-react with the free lambda 2 chain of the BALB/c myeloma protein T952 which differs from lambda 2(315) in five amino acid positions (38, 94, 95, 96, 99). Similarly, Th primed with free lambda 2T952 did not respond to a boost with free lambda 2(315). Thus, BALB/c lambda 2(315)-specific Th recognize an idiotope that depends on some or all of the residues at positions 94, 95, 96 and 99. Furthermore, free lambda 2T952 contains an idiotope immunogenic to Th that depends on some or all of residues 38, 94, 95, 96 and 99. Th recognition of the free lambda 2T952 idiotope was quenched upon H + L chain assembly because Th elicited by free lambda 2T952 did not respond to a boost with the complete T952 myeloma protein. In contrast to the lack of Th cell cross-reactivity, some of the antisera from BALB/c mice immunized with free lambda 2T952 cross-reacted with free lambda 2(315), free lambda lJ558 and free lambda 3CBPC49 but not with free kappa W3129 or polyclonal L chains. The H chain of T952 (alpha, kappa 2) myeloma protein was abnormally short (Mr = 48 000) and T952 existed as a halfmere probably due to this H chain deletion. Furthermore, H and L chains were disulfide bonded to each other.

Antibodies to granulocytes detected by an indirect immunofluorescence method not requiring chemical modification of cells

IgG antibodies to neutrophil polymorphonuclear cells (PMNs) were detected by a simple indirect immunofluorescence method that did not require chemical or enzymatic modification of the cells. Based on recent information about the human PMN Fc gamma-receptor, nonspecific binding of IgG to PMNs was virtually completely prevented by incubating cells at 37 degrees C with human serum diluted 1 to 3 in the presence of a high concentration of rabbit IgG. This also facilitated distinction of sera with weak anti-PMN activity from normal sera. On the other hand, nonspecific staining remained on a fraction (10-25%) of mononuclear leukocytes. Following first-time transfusion of 0.5 to 5 units of whole blood or red cell concentrate, 4 of 27 patients (15%) developed anti-leukocyte antibodies. Anti-leukocyte antibodies were detected in 51 percent of 47 patients with reported febrile transfusion reactions; the IgG antibodies bound to PMNs in 38 percent of these 47 patients. Since only about one in three patients with febrile transfusion reactions had detectable IgG anti-PMN antibodies, fever may be caused by lysis of leukocytes other than PMNs.

H-2-linked Ir genes have a striking influence on the immunogenicity of idiotopes of myeloma protein 315 for T helper cells

H-2-linked immune response (Ir) genes control T helper cells (Th) that recognize idiotopes of the V domains of myeloma protein 315 as carriers; Th recognition was detected by augmentation of antibody responses of hapten (4-hydroxy-3-iodo-5-nitrophenylacetyl (NIP]-primed B cells boosted with NIP conjugated to Fab315. The present study indicates that the responder k allele of the Ir VH315 gene maps to the I-A subregion of H-2. A responder s allele of the Ir V lambda 2(315) gene on an A-strain background was identified, which also most likely maps to I-A. Although the d allele of the Ir V lambda 2(315) gene is a responder allele on DBA/2 background, the D2.GD strain (with I-region haplotype AdBbJbEbCb) was non-responder to V lambda 2(315), suggesting either that the responder d allele maps to I-E or that the b allele of a second Ir V lambda 2(315) gene located to the right of I-A exerts a strong suppressive influence. The H-2b haplotype conferred non-responsiveness to VH315, V lambda 2(315), and Fv315.

Specificity of antibody and helper T-cell responses to the isologous myeloma protein W3129 and its subunits

The specificity of BALB/c antibodies and Th elicited by BALB/c myeloma protein W3129 (alpha, kappa) and its subunits was studied. Antibodies were detected with RIA and ELISA techniques. Th were demonstrated by their ability to augment a secondary anti-NIP antibody response in a Mitchison type assay of adoptive immunity. The major proportion of antibodies elicited by the complete W3129 was directed to an idiotypic determinant(s) that depended on assembled H + L chains. The determinant(s) was probably located in or near the antibody combining site because binding was hapten-inhibitable. A second minor antibody population bound an idiotypic determinant(s) on VW3129H expressed on isolated H-chain as well as on the complete myeloma protein. A third and very weakly reactive set of antibodies was specific for a C alpha antigenic site(s) which was expressed much more efficiently on free than on assembled alpha-chains. The antibody response to free kappa W3129 was directed to idiotypic determinants that were inaccessible in the complete molecule. By contrast, free kappa W3129 elicited Th that responded to an idiotypic determinant(s) on VW3129K; the determinant(s) was expressed on both the isolated chain and the complete W3129, suggesting that Th responded to an idiotope not recognized by B-cells. Priming with free alpha W3129 failed in four out of five experiments to induce Th that responded to the complete W3129, demonstrating that a major difference existed between VH and VL of W3129 regarding their immunogenicity for Th. Nevertheless, free alpha W3129 did elicit antibody responses that displayed high reactivity with the complete molecule, indicating that certain serologically defined antigenic sites on the surface of W3129 are also expressed on isolated alpha W3129. Thus, certain differences were detected as to the specificities of Th and B-cells for W3129 and its subunits since they recognized separate idiotopes located in the VL- or VH-region, respectively. The pattern of Th recognition of W3129 resembled that of another isologous myeloma protein, M315, but was unlike that of a third, J558, previously described from this laboratory.

Determinant-specific regulation of T helper cell responses to murine lambda light chains by both H-2 and non-H-2 genes

Previous work has revealed that the T helper cell (Th) responses to an antigenic determinant of V lambda 2(315) (called lambda 2.1) is regulated by both H-2 and non-H-2 genes. In the present study this was confirmed and extended to two other determinants, one shared between free lambda 2(315) and lambda 1(J558) (called lambda 2.2) and one unique for free lambda 1(J558) (called lambda 1.1). H-2 genes regulate the responses to the latter determinants, because BALB.B (H-2b) mice were low responders and BALB/c (H-2d) mice were high responders. Thus, the H-2d haplotype on BALB/c background was associated with high responder status. However, when the H-2d haplotype was examined on other genetic backgrounds than BALB/c, the animals could be classified as either intermediate or low responders, depending upon the non-H-2 background. This demonstrated that non-H-2 genes also influenced Th responses. Furthermore, C3H-H-2o, DBA/2 and B10.D2 mice (all H-2d) responded to only one (lambda 2.1) but not the other (lambda 2.2) of two determinants physically linked on the same polypeptide chain (lambda 2(315)). This indicated that the non-H-2 gene effect is capable of fine discrimination, i.e. the non-H-2 gene-mediated low responder phenotype may at least in part be due to failure of recognition of certain antigenic sites, like the H-2-linked Ir-gene defect. F1 hybrids responded to the same determinants as their parental strains; e.g., the BALB/c non-H-2 background exerted a dominant influence over the low responder background of C3H, B10 and DBA/2 strains.

T helper cells recognize an idiotope located on peptide 88-114/117 of the light chain variable domain of an isologous myeloma protein (315)

Isolated variable region light chain 315 (VL-315), the VL domain of a myeloma protein of BALB/c origin, induces T cells of BALB/c (H-2d) mice that help the adoptive secondary anti-4-hydroxy-3-iodo-5-nitrophenylacetyl (NIP) antibody response to NIP-Fab315. The location of the epitope recognized by helper cells was examined with two fragments of VL-315, obtained by cleavage with cyanogen bromide at Met 87. Both N-terminal fragment 1-86 and C-terminal fragment 88-114/117 elicited BALB/c antibodies that bound to the respective fragments and to VL-315. By contrast, only fragment 88-114/117, which consists of the third hypervariable region, J region, and 5-7 amino acids of the C region, induced helper cells that augmented the anti-NIP response to NIP-Fab 315.

Cultured human endothelial cells display an antigen that is recognized by certain human anti-chromatin autoantibodies

Certain human anti-nucleosome autoantibodies cross-reacted specifically with an antigen on the surface of human vascular endothelial cells. This was shown by two different techniques. First, antibodies eluted from the surface of cultured endothelial cells bound to cell nuclei; this binding was inhibited by soluble mononucleosomes. Second, X-ANA, specifically isolated by their affinity to polynucleosomes, stained the plasma membranes of single cell suspensions of endothelial cells in the indirect immunofluorescence test. Several lines of evidence excluded Fc receptor-mediated binding of Ig to the cells. Thus, plasma membranes of vascular endothelial cells and chromatin bear an antigen that is serologically related.